diff --git a/examples/generate_phpdoc.py b/examples/generate_phpdoc.py
index 0f2c60f..632db36 100755
--- a/examples/generate_phpdoc.py
+++ b/examples/generate_phpdoc.py
@@ -31,7 +31,9 @@
     GValue.array_int_type: 'integer[]|integer',
     GValue.array_double_type: 'float[]|float',
     GValue.array_image_type: 'Image[]|Image',
-    GValue.blob_type: 'string'
+    GValue.blob_type: 'string',
+    GValue.source_type: 'Source',
+    GValue.target_type: 'Target'
 }
 
 # php result type names are different, annoyingly, and very restricted
@@ -48,7 +50,9 @@
     GValue.array_int_type: 'array',
     GValue.array_double_type: 'array',
     GValue.array_image_type: 'array',
-    GValue.blob_type: 'string'
+    GValue.blob_type: 'string',
+    GValue.source_type: 'Source',
+    GValue.target_type: 'Target'
 }
 
 # values for VipsArgumentFlags
diff --git a/examples/streaming-bench.php b/examples/streaming-bench.php
new file mode 100644
index 0000000..1fcf04c
--- /dev/null
+++ b/examples/streaming-bench.php
@@ -0,0 +1,131 @@
+#!/usr/bin/env php
+<?php
+
+use Jcupitt\Vips\Config;
+use Jcupitt\Vips\Image;
+use Jcupitt\Vips\Source;
+use Jcupitt\Vips\SourceResource;
+use Jcupitt\Vips\Target;
+use Jcupitt\Vips\TargetResource;
+
+require dirname(__DIR__) . '/vendor/autoload.php';
+
+$doBenchmark = static function () {
+    $sourceOptions = ['access' => 'sequential'];
+    $sourceOptionString = 'access=sequential';
+    $iterations = 100;
+    $targetWidth = 100.0;
+    $targetSuffix = '.jpg';
+    $targetOptions = ['optimize-coding' => true, 'strip' => true, 'Q' => 100, 'profile' => 'srgb'];
+    $targetFile = dirname(__DIR__) . "/tests/images/target.jpg";
+    $sourceFile = dirname(__DIR__) . '/tests/images/img_0076.jpg';
+
+### Callbacks
+    $start = microtime(true);
+
+    for ($i = 0; $i < $iterations; $i++) {
+        $source = new SourceResource(fopen($sourceFile, 'rb'));
+        $target = new TargetResource(fopen($targetFile, 'wb+'));
+        $image = Image::newFromSource($source, '', $sourceOptions);
+        $image = $image->resize($targetWidth / $image->width);
+        $image->writeToTarget(
+            $target,
+            $targetSuffix,
+            $targetOptions
+        );
+        unlink($targetFile);
+    }
+
+    echo (microtime(true) - $start) . ' Seconds for Streaming with callbacks' . PHP_EOL;
+
+### Builtin
+    $start = microtime(true);
+
+    for ($i = 0; $i < $iterations; $i++) {
+        $source = Source::newFromFile($sourceFile);
+        $target = Target::newToFile($targetFile);
+        $image = Image::newFromSource($source, '', $sourceOptions);
+        $image = $image->resize($targetWidth / $image->width);
+        $image->writeToTarget(
+            $target,
+            $targetSuffix,
+            $targetOptions
+        );
+        unlink($targetFile);
+    }
+
+    echo (microtime(true) - $start) . ' Seconds for Streaming with builtin source/target' . PHP_EOL;
+
+### Callbacks Thumbnail
+    $start = microtime(true);
+
+    for ($i = 0; $i < $iterations; $i++) {
+        $source = new SourceResource(fopen($sourceFile, 'rb'));
+        $target = new TargetResource(fopen($targetFile, 'wb+'));
+        $image = Image::thumbnail_source($source, $targetWidth);
+        $image->writeToTarget(
+            $target,
+            $targetSuffix,
+            $targetOptions
+        );
+        unlink($targetFile);
+    }
+
+    echo (microtime(true) - $start) . ' Seconds for Streaming Thumbnail with callbacks' . PHP_EOL;
+
+### Builtin Thumbnail
+    $start = microtime(true);
+
+    for ($i = 0; $i < $iterations; $i++) {
+        $source = Source::newFromFile($sourceFile);
+        $target = Target::newToFile($targetFile);
+        $image = Image::thumbnail_source($source, $targetWidth);
+        $image->writeToTarget(
+            $target,
+            $targetSuffix,
+            $targetOptions
+        );
+        unlink($targetFile);
+    }
+
+    echo (microtime(true) - $start) . ' Seconds for Streaming Thumbnail with builtin source/target' . PHP_EOL;
+
+### Thumbnail
+    $start = microtime(true);
+
+    for ($i = 0; $i < $iterations; $i++) {
+        $image = Image::thumbnail($sourceFile . "[$sourceOptionString]", $targetWidth);
+        $image->writeToFile(
+            $targetFile,
+            $targetOptions
+        );
+        unlink($targetFile);
+    }
+
+    echo (microtime(true) - $start) . ' Seconds for Thumbnail API' . PHP_EOL;
+
+### Classic
+    $start = microtime(true);
+
+    for ($i = 0; $i < $iterations; $i++) {
+        $image = Image::newFromFile($sourceFile, $sourceOptions);
+        $image = $image->resize($targetWidth / $image->width);
+        $image->writeToFile(
+            $targetFile,
+            $targetOptions
+        );
+        unlink($targetFile);
+    }
+
+    echo (microtime(true) - $start) . ' Seconds for Classic API' . PHP_EOL;
+};
+
+$doBenchmark();
+
+//echo "=== NOW NO CACHE ===" . PHP_EOL;
+//
+//Config::cacheSetMax(0);
+//Config::cacheSetMaxFiles(0);
+//Config::cacheSetMaxMem(0);
+//
+//$doBenchmark();
diff --git a/examples/streaming.php b/examples/streaming.php
new file mode 100644
index 0000000..f5628e2
--- /dev/null
+++ b/examples/streaming.php
@@ -0,0 +1,12 @@
+#!/usr/bin/env php
+<?php
+
+require dirname(__DIR__) . '/vendor/autoload.php';
+
+use Jcupitt\Vips;
+use Jcupitt\Vips\Source;
+
+$source = Source::newFromFile(dirname(__DIR__) . '/tests/images/img_0076.jpg');
+$target = Vips\Target::newToFile(dirname(__DIR__) . "/tests/images/target.jpg");
+$image = Vips\Image::newFromSource($source);
+$image->writeToTarget($target, '.jpg[Q=95]');
diff --git a/src/Connection.php b/src/Connection.php
new file mode 100644
index 0000000..ea38166
--- /dev/null
+++ b/src/Connection.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Jcupitt\Vips;
+
+abstract class Connection extends VipsObject
+{
+    /**
+     * A pointer to the underlying Connection. This is the same as the
+     * GObject, just cast to Connection to help FFI.
+     *
+     * @internal
+     */
+    public \FFI\CData $pointer;
+
+    public function __construct(\FFI\CData $pointer)
+    {
+        $this->pointer = \FFI::cast(FFI::ctypes('VipsConnection'), $pointer);
+        parent::__construct($pointer);
+    }
+
+    /**
+     * Get the filename associated with a connection. Return null if there is no associated file.
+     */
+    public function filename(): ?string
+    {
+        return FFI::vips()->vips_connection_filename($this->pointer);
+    }
+
+    /**
+     * Make a human-readable name for a connection suitable for error messages.
+     */
+    public function nick(): ?string
+    {
+        return FFI::vips()->vips_connection_nick($this->pointer);
+    }
+}
diff --git a/src/FFI.php b/src/FFI.php
index b76c8bf..f6cb23d 100644
--- a/src/FFI.php
+++ b/src/FFI.php
@@ -178,6 +178,18 @@ public static function shutDown(): void
         self::vips()->vips_shutdown();
     }
 
+    public static function newGClosure(): \FFI\CData
+    {
+        // GClosure measures 32-bit with the first few fields until marshal
+        // Marshal is a function pointer, thus platform-dependant.
+        // Data is a pointer, thus platform-dependant.
+        // Notifiers is an array-pointer, thus platform-dependant.
+        // All in all it's basically 4 (bytes) + 3 * POINTER_SIZE
+        // However, gobject wants 8 (bytes) + 3 * POINTER_SIZE.
+        // I'm not sure where that extra byte comes from. Padding on 64-bit machines?
+        return self::gobject()->g_closure_new_simple(8 + 3 * PHP_INT_SIZE, null);
+    }
+
     private static function libraryName(string $name, int $abi): string
     {
         switch (PHP_OS_FAMILY) {
@@ -302,6 +314,7 @@ private static function init(): void
 typedef int32_t gint32;
 typedef uint64_t guint64;
 typedef int64_t gint64;
+typedef void* gpointer;
 
 typedef $gtype GType;
 
@@ -366,6 +379,7 @@ private static function init(): void
 void g_value_set_flags (GValue* value, unsigned int f);
 void g_value_set_string (GValue* value, const char* str);
 void g_value_set_object (GValue* value, void* object);
+void g_value_set_pointer (GValue* value, gpointer pointer);
 
 bool g_value_get_boolean (const GValue* value);
 int g_value_get_int (GValue* value);
@@ -376,6 +390,7 @@ private static function init(): void
 unsigned int g_value_get_flags (GValue* value);
 const char* g_value_get_string (GValue* value);
 void* g_value_get_object (GValue* value);
+gpointer g_value_get_pointer (GValue* value);
 
 typedef struct _GEnumValue {
     int value;
@@ -429,6 +444,19 @@ private static function init(): void
     int connect_flags);
 
 const char* g_param_spec_get_blurb (GParamSpec* psp);
+
+typedef void *GClosure;
+typedef void (*marshaler)(
+    struct GClosure* closure, 
+    GValue* return_value, 
+    int n_param_values, 
+    const GValue* param_values, 
+    void* invocation_hint, 
+    void* marshal_data
+);
+void g_closure_set_marshal(GClosure* closure, marshaler marshal);
+long g_signal_connect_closure(GObject* object, const char* detailed_signal, GClosure *closure, bool after);
+GClosure* g_closure_new_simple (int sizeof_closure, void* data);
 EOS;
 
         # the whole libvips API, mostly adapted from pyvips
@@ -703,12 +731,6 @@ private static function init(): void
 
 VipsSourceCustom* vips_source_custom_new (void);
 
-// FIXME ... these need porting to php-ffi
-// extern "Python" gint64 _marshal_read (VipsSource*,
-//    void*, gint64, void*);
-// extern "Python" gint64 _marshal_seek (VipsSource*,
-//    gint64, int, void*);
-
 typedef struct _VipsTarget {
     VipsConnection parent_object;
 
@@ -752,11 +774,17 @@ private static function init(): void
         // look these up in advance
         self::$ctypes = [
             "GObject" => self::$gobject->type("GObject*"),
+            "GClosure" => self::$gobject->type("GClosure"),
             "GParamSpec" => self::$gobject->type("GParamSpec*"),
             "VipsObject" => self::$vips->type("VipsObject*"),
             "VipsOperation" => self::$vips->type("VipsOperation*"),
             "VipsImage" => self::$vips->type("VipsImage*"),
             "VipsInterpolate" => self::$vips->type("VipsInterpolate*"),
+            "VipsConnection" => self::$vips->type("VipsConnection*"),
+            "VipsSource" => self::$vips->type("VipsSource*"),
+            "VipsSourceCustom" => self::$vips->type("VipsSourceCustom*"),
+            "VipsTarget" => self::$vips->type("VipsTarget*"),
+            "VipsTargetCustom" => self::$vips->type("VipsTargetCustom*"),
         ];
 
         self::$gtypes = [
@@ -780,6 +808,8 @@ private static function init(): void
 
             "GObject" => self::$gobject->g_type_from_name("GObject"),
             "VipsImage" => self::$gobject->g_type_from_name("VipsImage"),
+
+            "GClosure" => self::$gobject->g_type_from_name("GClosure"),
         ];
 
         // map vips format names to c type names
diff --git a/src/ForeignDzLayout.php b/src/ForeignDzLayout.php
index ae36259..021d75f 100644
--- a/src/ForeignDzLayout.php
+++ b/src/ForeignDzLayout.php
@@ -53,5 +53,4 @@ abstract class ForeignDzLayout
     const ZOOMIFY = 'zoomify';
     const GOOGLE = 'google';
     const IIIF = 'iiif';
-    const IIIF3 = 'iiif3';
 }
diff --git a/src/GObject.php b/src/GObject.php
index 4ebc500..0047e20 100644
--- a/src/GObject.php
+++ b/src/GObject.php
@@ -38,6 +38,9 @@
 
 namespace Jcupitt\Vips;
 
+use Closure;
+use FFI\CData;
+
 /**
  * This class holds a pointer to a GObject and manages object lifetime.
  *
@@ -55,7 +58,7 @@ abstract class GObject
      *
      * @internal
      */
-    private \FFI\CData $pointer;
+    private CData $pointer;
 
     /**
      * Wrap a GObject around an underlying vips resource. The GObject takes
@@ -64,12 +67,12 @@ abstract class GObject
      * Don't call this yourself, users should stick to (for example)
      * Image::newFromFile().
      *
-     * @param FFI\CData $pointer The underlying pointer that this
+     * @param CData $pointer The underlying pointer that this
      *  object should wrap.
      *
      * @internal
      */
-    public function __construct(\FFI\CData $pointer)
+    public function __construct(CData $pointer)
     {
         $this->pointer = \FFI::cast(FFI::ctypes("GObject"), $pointer);
     }
@@ -94,7 +97,164 @@ public function unref(): void
         FFI::gobject()->g_object_unref($this->pointer);
     }
 
-    // TODO signal marshalling to go in
+    /**
+     * Connect to a signal on this object.
+     * The callback will be triggered every time this signal is issued on this instance.
+     * @throws Exception
+     */
+    public function signalConnect(string $name, callable $callback): void
+    {
+        $marshaler = self::getMarshaler($name, $callback);
+        if ($marshaler === null) {
+            throw new Exception("unsupported signal $name");
+        }
+
+        $gc = FFI::newGClosure();
+        FFI::gobject()->g_closure_set_marshal($gc, $marshaler);
+        FFI::gobject()->g_signal_connect_closure($this->pointer, $name, $gc, 0);
+    }
+
+    private static function getMarshaler(string $name, callable $callback): ?Closure
+    {
+        switch ($name) {
+            case 'preeval':
+            case 'eval':
+            case 'posteval':
+                return static function (
+                    CData  $gClosure,
+                    ?CData $returnValue,
+                    int    $numberOfParams,
+                    CData  $params,
+                    CData  $hint,
+                    ?CData $data
+                ) use (&$callback) {
+                    assert($numberOfParams === 3);
+                    /**
+                     * Signature: void(VipsImage* image, void* progress, void* handle)
+                     */
+                    $vi = FFI::gobject()->g_value_get_object(\FFI::addr($params[0]));
+                    FFI::gobject()->g_object_ref($vi);
+                    $image = new Image($vi);
+                    $pr = \FFI::cast(
+                        FFI::ctypes('VipsProgress'),
+                        FFI::gobject()->g_value_get_pointer(\FFI::addr($params[1]))
+                    );
+                    $callback($image, $pr);
+                };
+            case 'read':
+                if (FFI::atLeast(8, 9)) {
+                    return static function (
+                        CData  $gClosure,
+                        CData  $returnValue,
+                        int    $numberOfParams,
+                        CData  $params,
+                        CData  $hint,
+                        ?CData $data
+                    ) use (&$callback): void {
+                        assert($numberOfParams === 4);
+                        /*
+                         * Signature: gint64(VipsSourceCustom* source, void* buffer, gint64 length, void* handle)
+                         */
+                        $bufferLength = (int)FFI::gobject()->g_value_get_int64(\FFI::addr($params[2]));
+                        $returnBuffer = $callback($bufferLength);
+                        $returnBufferLength = 0;
+
+                        if ($returnBuffer !== null) {
+                            $returnBufferLength = strlen($returnBuffer);
+                            $bufferPointer = FFI::gobject()->g_value_get_pointer(\FFI::addr($params[1]));
+                            \FFI::memcpy($bufferPointer, $returnBuffer, $returnBufferLength);
+                        }
+                        FFI::gobject()->g_value_set_int64($returnValue, $returnBufferLength);
+                    };
+                }
+
+                return null;
+            case 'seek':
+                if (FFI::atLeast(8, 9)) {
+                    return static function (
+                        CData  $gClosure,
+                        CData  $returnValue,
+                        int    $numberOfParams,
+                        CData  $params,
+                        CData  $hint,
+                        ?CData $data
+                    ) use (&$callback): void {
+                        assert($numberOfParams === 4);
+                        /*
+                         * Signature: gint64(VipsSourceCustom* source, gint64 offset, int whence, void* handle)
+                         */
+                        $offset = (int)FFI::gobject()->g_value_get_int64(\FFI::addr($params[1]));
+                        $whence = (int)FFI::gobject()->g_value_get_int(\FFI::addr($params[2]));
+                        FFI::gobject()->g_value_set_int64($returnValue, $callback($offset, $whence));
+                    };
+                }
+
+                return null;
+            case 'write':
+                if (FFI::atLeast(8, 9)) {
+                    return static function (
+                        CData  $gClosure,
+                        CData  $returnValue,
+                        int    $numberOfParams,
+                        CData  $params,
+                        CData  $hint,
+                        ?CData $data
+                    ) use (&$callback): void {
+                        assert($numberOfParams === 4);
+                        /*
+                         * Signature: gint64(VipsTargetCustom* target, void* buffer, gint64 length, void* handle)
+                         */
+                        $bufferPointer = FFI::gobject()->g_value_get_pointer(\FFI::addr($params[1]));
+                        $bufferLength = (int)FFI::gobject()->g_value_get_int64(\FFI::addr($params[2]));
+                        $buffer = \FFI::string($bufferPointer, $bufferLength);
+                        $returnBufferLength = $callback($buffer);
+                        FFI::gobject()->g_value_set_int64($returnValue, $returnBufferLength);
+                    };
+                }
+
+                return null;
+            case 'finish':
+                if (FFI::atLeast(8, 9)) {
+                    return static function (
+                        CData  $gClosure,
+                        ?CData $returnValue,
+                        int    $numberOfParams,
+                        CData  $params,
+                        CData  $hint,
+                        ?CData $data
+                    ) use (&$callback): void {
+                        assert($numberOfParams === 2);
+                        /**
+                         * Signature: void(VipsTargetCustom* target, void* handle)
+                         */
+                        $callback();
+                    };
+                }
+
+                return null;
+            case 'end':
+                if (FFI::atLeast(8, 13)) {
+                    return static function (
+                        CData  $gClosure,
+                        CData  $returnValue,
+                        int    $numberOfParams,
+                        CData  $params,
+                        CData  $hint,
+                        ?CData $data
+                    ) use (&$callback): void {
+                        assert($numberOfParams === 2);
+                        /**
+                         * Signature: int(VipsTargetCustom* target, void* handle)
+                         */
+                        FFI::gobject()->g_value_set_int($returnValue, $callback());
+                    };
+                }
+
+                return null;
+            default:
+                return null;
+        }
+    }
 }
 
 /*
diff --git a/src/GValue.php b/src/GValue.php
index 6478352..c310e6a 100644
--- a/src/GValue.php
+++ b/src/GValue.php
@@ -188,9 +188,7 @@ public function set($value): void
                 # can own and free
                 $n = strlen($value);
                 $memory = \FFI::new("char[$n]", false, true);
-                for ($i = 0; $i < $n; $i++) {
-                    $memory[$i] = $value[$i];
-                }
+                \FFI::memcpy($memory, $value, $n);
                 FFI::vips()->
                     vips_value_set_blob_free($this->pointer, $memory, $n);
                 break;
diff --git a/src/GsfOutputCsvQuotingMode.php b/src/GsfOutputCsvQuotingMode.php
new file mode 100644
index 0000000..a8a08f0
--- /dev/null
+++ b/src/GsfOutputCsvQuotingMode.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * This file was generated automatically. Do not edit!
+ *
+ * PHP version 7
+ *
+ * LICENSE:
+ *
+ * Copyright (c) 2016 John Cupitt
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * @category  Images
+ * @package   Jcupitt\Vips
+ * @author    John Cupitt <jcupitt@gmail.com>
+ * @copyright 2016 John Cupitt
+ * @license   https://opensource.org/licenses/MIT MIT
+ * @link      https://github.com/jcupitt/php-vips
+ */
+
+namespace Jcupitt\Vips;
+
+/**
+ * The GsfOutputCsvQuotingMode enum.
+ * @category  Images
+ * @package   Jcupitt\Vips
+ * @author    John Cupitt <jcupitt@gmail.com>
+ * @copyright 2016 John Cupitt
+ * @license   https://opensource.org/licenses/MIT MIT
+ * @link      https://github.com/jcupitt/php-vips
+ */
+abstract class GsfOutputCsvQuotingMode
+{
+    const NEVER = 'never';
+    const AUTO = 'auto';
+}
diff --git a/src/Image.php b/src/Image.php
index bbddf07..5701de2 100644
--- a/src/Image.php
+++ b/src/Image.php
@@ -901,6 +901,38 @@ public function newFromImage($value): Image
         ]);
     }
 
+    /**
+     * Find the name of the load operation vips will use to load a VipsSource, for
+     * example 'VipsForeignLoadJpegSource'. You can use this to work out what
+     * options to pass to newFromSource().
+     *
+     * @param Source $source The source to test
+     * @return string|null The name of the load operation, or null.
+     */
+    public static function findLoadSource(Source $source): ?string
+    {
+        return FFI::vips()->vips_foreign_find_load_source(\FFI::cast(FFI::ctypes('VipsSource'), $source->pointer));
+    }
+
+    /**
+     * @throws Exception
+     */
+    public static function newFromSource(Source $source, string $string_options = '', array $options = []): self
+    {
+        $loader = self::findLoadSource($source);
+        if ($loader === null) {
+            throw new Exception('unable to load from source');
+        }
+
+        if ($string_options !== '') {
+            $options = array_merge([
+                "string_options" => $string_options,
+            ], $options);
+        }
+
+        return VipsOperation::call($loader, null, [$source], $options);
+    }
+
     /**
      * Write an image to a file.
      *
@@ -1040,6 +1072,28 @@ public function writeToArray(): array
         return $result;
     }
 
+    /**
+     * @throws Exception
+     */
+    public function writeToTarget(Target $target, string $suffix, array $options = []): void
+    {
+        $filename = Utils::filenameGetFilename($suffix);
+        $string_options = Utils::filenameGetOptions($suffix);
+        $saver = FFI::vips()->vips_foreign_find_save_target($filename);
+
+        if ($saver === '') {
+            throw new Exception("can't save to target with given suffix $filename");
+        }
+
+        if ($string_options !== '') {
+            $options = array_merge([
+                "string_options" => $string_options,
+            ], $options);
+        }
+
+        VipsOperation::call($saver, $this, [$target], $options);
+    }
+
     /**
      * Copy to memory.
      *
diff --git a/src/ImageAutodoc.php b/src/ImageAutodoc.php
index 529c834..36f017b 100644
--- a/src/ImageAutodoc.php
+++ b/src/ImageAutodoc.php
@@ -171,11 +171,11 @@
  *     @throws Exception
  * @method static Image csvload(string $filename, array $options = []) Load csv.
  *     @throws Exception
- * @method static Image csvload_source(string $source, array $options = []) Load csv.
+ * @method static Image csvload_source(Source $source, array $options = []) Load csv.
  *     @throws Exception
  * @method void csvsave(string $filename, array $options = []) Save image to csv.
  *     @throws Exception
- * @method void csvsave_target(string $target, array $options = []) Save image to csv.
+ * @method void csvsave_target(Target $target, array $options = []) Save image to csv.
  *     @throws Exception
  * @method Image dE00(Image $right, array $options = []) Calculate dE00.
  *     @throws Exception
@@ -203,8 +203,6 @@
  *     @throws Exception
  * @method string dzsave_buffer(array $options = []) Save image to dz buffer.
  *     @throws Exception
- * @method void dzsave_target(string $target, array $options = []) Save image to deepzoom target.
- *     @throws Exception
  * @method Image embed(integer $x, integer $y, integer $width, integer $height, array $options = []) Embed an image in a larger image.
  *     @throws Exception
  * @method Image extract_area(integer $left, integer $top, integer $width, integer $height, array $options = []) Extract an area from an image.
@@ -229,7 +227,7 @@
  *     @throws Exception
  * @method static Image fitsload(string $filename, array $options = []) Load a FITS image.
  *     @throws Exception
- * @method static Image fitsload_source(string $source, array $options = []) Load FITS from a source.
+ * @method static Image fitsload_source(Source $source, array $options = []) Load FITS from a source.
  *     @throws Exception
  * @method void fitssave(string $filename, array $options = []) Save image to fits file.
  *     @throws Exception
@@ -260,13 +258,7 @@
  *     @throws Exception
  * @method static Image gifload_buffer(string $buffer, array $options = []) Load GIF with libnsgif.
  *     @throws Exception
- * @method static Image gifload_source(string $source, array $options = []) Load gif from source.
- *     @throws Exception
- * @method void gifsave(string $filename, array $options = []) Save as gif.
- *     @throws Exception
- * @method string gifsave_buffer(array $options = []) Save as gif.
- *     @throws Exception
- * @method void gifsave_target(string $target, array $options = []) Save as gif.
+ * @method static Image gifload_source(Source $source, array $options = []) Load gif from source.
  *     @throws Exception
  * @method Image globalbalance(array $options = []) Global balance an image mosaic.
  *     @throws Exception
@@ -281,13 +273,13 @@
  *     @throws Exception
  * @method static Image heifload_buffer(string $buffer, array $options = []) Load a HEIF image.
  *     @throws Exception
- * @method static Image heifload_source(string $source, array $options = []) Load a HEIF image.
+ * @method static Image heifload_source(Source $source, array $options = []) Load a HEIF image.
  *     @throws Exception
  * @method void heifsave(string $filename, array $options = []) Save image in HEIF format.
  *     @throws Exception
  * @method string heifsave_buffer(array $options = []) Save image in HEIF format.
  *     @throws Exception
- * @method void heifsave_target(string $target, array $options = []) Save image in HEIF format.
+ * @method void heifsave_target(Target $target, array $options = []) Save image in HEIF format.
  *     @throws Exception
  * @method Image hist_cum(array $options = []) Form cumulative histogram.
  *     @throws Exception
@@ -334,23 +326,11 @@
  * @method Image join(Image $in2, string $direction, array $options = []) Join a pair of images.
  *     @see Direction for possible values for $direction
  *     @throws Exception
- * @method static Image jp2kload(string $filename, array $options = []) Load JPEG2000 image.
- *     @throws Exception
- * @method static Image jp2kload_buffer(string $buffer, array $options = []) Load JPEG2000 image.
- *     @throws Exception
- * @method static Image jp2kload_source(string $source, array $options = []) Load JPEG2000 image.
- *     @throws Exception
- * @method void jp2ksave(string $filename, array $options = []) Save image in JPEG2000 format.
- *     @throws Exception
- * @method string jp2ksave_buffer(array $options = []) Save image in JPEG2000 format.
- *     @throws Exception
- * @method void jp2ksave_target(string $target, array $options = []) Save image in JPEG2000 format.
- *     @throws Exception
  * @method static Image jpegload(string $filename, array $options = []) Load jpeg from file.
  *     @throws Exception
  * @method static Image jpegload_buffer(string $buffer, array $options = []) Load jpeg from buffer.
  *     @throws Exception
- * @method static Image jpegload_source(string $source, array $options = []) Load image from jpeg source.
+ * @method static Image jpegload_source(Source $source, array $options = []) Load image from jpeg source.
  *     @throws Exception
  * @method void jpegsave(string $filename, array $options = []) Save image to jpeg file.
  *     @throws Exception
@@ -358,19 +338,19 @@
  *     @throws Exception
  * @method void jpegsave_mime(array $options = []) Save image to jpeg mime.
  *     @throws Exception
- * @method void jpegsave_target(string $target, array $options = []) Save image to jpeg target.
+ * @method void jpegsave_target(Target $target, array $options = []) Save image to jpeg target.
  *     @throws Exception
  * @method static Image jxlload(string $filename, array $options = []) Load JPEG-XL image.
  *     @throws Exception
  * @method static Image jxlload_buffer(string $buffer, array $options = []) Load JPEG-XL image.
  *     @throws Exception
- * @method static Image jxlload_source(string $source, array $options = []) Load JPEG-XL image.
+ * @method static Image jxlload_source(Source $source, array $options = []) Load JPEG-XL image.
  *     @throws Exception
  * @method void jxlsave(string $filename, array $options = []) Save image in JPEG-XL format.
  *     @throws Exception
  * @method string jxlsave_buffer(array $options = []) Save image in JPEG-XL format.
  *     @throws Exception
- * @method void jxlsave_target(string $target, array $options = []) Save image in JPEG-XL format.
+ * @method void jxlsave_target(Target $target, array $options = []) Save image in JPEG-XL format.
  *     @throws Exception
  * @method Image labelregions(array $options = []) Label regions in an image.
  *     @throws Exception
@@ -378,7 +358,7 @@
  *     @throws Exception
  * @method Image linecache(array $options = []) Cache an image as a set of lines.
  *     @throws Exception
- * @method static Image logmat(float $sigma, float $min_ampl, array $options = []) Make a Laplacian of Gaussian image.
+ * @method static Image logmat(float $sigma, float $min_ampl, array $options = []) Make a laplacian of gaussian image.
  *     @throws Exception
  * @method static Image magickload(string $filename, array $options = []) Load file with ImageMagick.
  *     @throws Exception
@@ -429,13 +409,13 @@
  *     @throws Exception
  * @method static Image matrixload(string $filename, array $options = []) Load matrix.
  *     @throws Exception
- * @method static Image matrixload_source(string $source, array $options = []) Load matrix.
+ * @method static Image matrixload_source(Source $source, array $options = []) Load matrix.
  *     @throws Exception
  * @method void matrixprint(array $options = []) Print matrix.
  *     @throws Exception
  * @method void matrixsave(string $filename, array $options = []) Save image to matrix.
  *     @throws Exception
- * @method void matrixsave_target(string $target, array $options = []) Save image to matrix.
+ * @method void matrixsave_target(Target $target, array $options = []) Save image to matrix.
  *     @throws Exception
  * @method float max(array $options = []) Find image maximum.
  *     @throws Exception
@@ -457,23 +437,17 @@
  *     @throws Exception
  * @method Image msb(array $options = []) Pick most-significant byte from an image.
  *     @throws Exception
- * @method static Image niftiload(string $filename, array $options = []) Load NIfTI volume.
- *     @throws Exception
- * @method static Image niftiload_source(string $source, array $options = []) Load NIfTI volumes.
- *     @throws Exception
- * @method void niftisave(string $filename, array $options = []) Save image to nifti file.
- *     @throws Exception
  * @method static Image openexrload(string $filename, array $options = []) Load an OpenEXR image.
  *     @throws Exception
  * @method static Image openslideload(string $filename, array $options = []) Load file with OpenSlide.
  *     @throws Exception
- * @method static Image openslideload_source(string $source, array $options = []) Load source with OpenSlide.
+ * @method static Image openslideload_source(Source $source, array $options = []) Load source with OpenSlide.
  *     @throws Exception
  * @method static Image pdfload(string $filename, array $options = []) Load PDF from file.
  *     @throws Exception
  * @method static Image pdfload_buffer(string $buffer, array $options = []) Load PDF from buffer.
  *     @throws Exception
- * @method static Image pdfload_source(string $source, array $options = []) Load PDF from source.
+ * @method static Image pdfload_source(Source $source, array $options = []) Load PDF from source.
  *     @throws Exception
  * @method integer percent(float $percent, array $options = []) Find threshold for percent of pixels.
  *     @throws Exception
@@ -485,21 +459,21 @@
  *     @throws Exception
  * @method static Image pngload_buffer(string $buffer, array $options = []) Load png from buffer.
  *     @throws Exception
- * @method static Image pngload_source(string $source, array $options = []) Load png from source.
+ * @method static Image pngload_source(Source $source, array $options = []) Load png from source.
  *     @throws Exception
- * @method void pngsave(string $filename, array $options = []) Save image to file as PNG.
+ * @method void pngsave(string $filename, array $options = []) Save image to png file.
  *     @throws Exception
- * @method string pngsave_buffer(array $options = []) Save image to buffer as PNG.
+ * @method string pngsave_buffer(array $options = []) Save image to png buffer.
  *     @throws Exception
- * @method void pngsave_target(string $target, array $options = []) Save image to target as PNG.
+ * @method void pngsave_target(Target $target, array $options = []) Save image to target as PNG.
  *     @throws Exception
  * @method static Image ppmload(string $filename, array $options = []) Load ppm from file.
  *     @throws Exception
- * @method static Image ppmload_source(string $source, array $options = []) Load ppm base class.
+ * @method static Image ppmload_source(Source $source, array $options = []) Load ppm base class.
  *     @throws Exception
  * @method void ppmsave(string $filename, array $options = []) Save image to ppm file.
  *     @throws Exception
- * @method void ppmsave_target(string $target, array $options = []) Save to ppm.
+ * @method void ppmsave_target(Target $target, array $options = []) Save to ppm.
  *     @throws Exception
  * @method Image premultiply(array $options = []) Premultiply image alpha.
  *     @throws Exception
@@ -525,13 +499,13 @@
  *     @throws Exception
  * @method static Image radload_buffer(string $buffer, array $options = []) Load rad from buffer.
  *     @throws Exception
- * @method static Image radload_source(string $source, array $options = []) Load rad from source.
+ * @method static Image radload_source(Source $source, array $options = []) Load rad from source.
  *     @throws Exception
  * @method void radsave(string $filename, array $options = []) Save image to Radiance file.
  *     @throws Exception
  * @method string radsave_buffer(array $options = []) Save image to Radiance buffer.
  *     @throws Exception
- * @method void radsave_target(string $target, array $options = []) Save image to Radiance target.
+ * @method void radsave_target(Target $target, array $options = []) Save image to Radiance target.
  *     @throws Exception
  * @method Image rank(integer $width, integer $height, integer $index, array $options = []) Rank filter.
  *     @throws Exception
@@ -619,7 +593,7 @@
  *     @throws Exception
  * @method static Image svgload_buffer(string $buffer, array $options = []) Load SVG with rsvg.
  *     @throws Exception
- * @method static Image svgload_source(string $source, array $options = []) Load svg from source.
+ * @method static Image svgload_source(Source $source, array $options = []) Load svg from source.
  *     @throws Exception
  * @method static Image switch(Image[]|Image $tests, array $options = []) Find the index of the first non-zero pixel in tests.
  *     @throws Exception
@@ -633,20 +607,18 @@
  *     @throws Exception
  * @method Image thumbnail_image(integer $width, array $options = []) Generate thumbnail from image.
  *     @throws Exception
- * @method static Image thumbnail_source(string $source, integer $width, array $options = []) Generate thumbnail from source.
+ * @method static Image thumbnail_source(Source $source, integer $width, array $options = []) Generate thumbnail from source.
  *     @throws Exception
  * @method static Image tiffload(string $filename, array $options = []) Load tiff from file.
  *     @throws Exception
  * @method static Image tiffload_buffer(string $buffer, array $options = []) Load tiff from buffer.
  *     @throws Exception
- * @method static Image tiffload_source(string $source, array $options = []) Load tiff from source.
+ * @method static Image tiffload_source(Source $source, array $options = []) Load tiff from source.
  *     @throws Exception
  * @method void tiffsave(string $filename, array $options = []) Save image to tiff file.
  *     @throws Exception
  * @method string tiffsave_buffer(array $options = []) Save image to tiff buffer.
  *     @throws Exception
- * @method void tiffsave_target(string $target, array $options = []) Save image to tiff target.
- *     @throws Exception
  * @method Image tilecache(array $options = []) Cache an image as a set of tiles.
  *     @throws Exception
  * @method static Image tonelut(array $options = []) Build a look-up table.
@@ -657,23 +629,23 @@
  *     @throws Exception
  * @method static Image vipsload(string $filename, array $options = []) Load vips from file.
  *     @throws Exception
- * @method static Image vipsload_source(string $source, array $options = []) Load vips from source.
+ * @method static Image vipsload_source(Source $source, array $options = []) Load vips from source.
  *     @throws Exception
  * @method void vipssave(string $filename, array $options = []) Save image to file in vips format.
  *     @throws Exception
- * @method void vipssave_target(string $target, array $options = []) Save image to target in vips format.
+ * @method void vipssave_target(Target $target, array $options = []) Save image to target in vips format.
  *     @throws Exception
  * @method static Image webpload(string $filename, array $options = []) Load webp from file.
  *     @throws Exception
  * @method static Image webpload_buffer(string $buffer, array $options = []) Load webp from buffer.
  *     @throws Exception
- * @method static Image webpload_source(string $source, array $options = []) Load webp from source.
+ * @method static Image webpload_source(Source $source, array $options = []) Load webp from source.
  *     @throws Exception
  * @method void webpsave(string $filename, array $options = []) Save image to webp file.
  *     @throws Exception
  * @method string webpsave_buffer(array $options = []) Save image to webp buffer.
  *     @throws Exception
- * @method void webpsave_target(string $target, array $options = []) Save image to webp target.
+ * @method void webpsave_target(Target $target, array $options = []) Save image to webp target.
  *     @throws Exception
  * @method static Image worley(integer $width, integer $height, array $options = []) Make a worley noise image.
  *     @throws Exception
diff --git a/src/OperationMath.php b/src/OperationMath.php
index 857b488..52ffef1 100644
--- a/src/OperationMath.php
+++ b/src/OperationMath.php
@@ -59,10 +59,4 @@ abstract class OperationMath
     const LOG10 = 'log10';
     const EXP = 'exp';
     const EXP10 = 'exp10';
-    const SINH = 'sinh';
-    const COSH = 'cosh';
-    const TANH = 'tanh';
-    const ASINH = 'asinh';
-    const ACOSH = 'acosh';
-    const ATANH = 'atanh';
 }
diff --git a/src/OperationMath2.php b/src/OperationMath2.php
index b1fc69e..9e86093 100644
--- a/src/OperationMath2.php
+++ b/src/OperationMath2.php
@@ -51,5 +51,4 @@ abstract class OperationMath2
 {
     const POW = 'pow';
     const WOP = 'wop';
-    const ATAN2 = 'atan2';
 }
diff --git a/src/Source.php b/src/Source.php
new file mode 100644
index 0000000..60975fe
--- /dev/null
+++ b/src/Source.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Jcupitt\Vips;
+
+class Source extends Connection
+{
+    /**
+     * A pointer to the underlying VipsSource. This is the same as the
+     * GObject, just cast to VipsSource to help FFI.
+     *
+     * @internal
+     */
+    public \FFI\CData $pointer;
+
+    public function __construct(\FFI\CData $pointer)
+    {
+        $this->pointer = \FFI::cast(FFI::ctypes('VipsSource'), $pointer);
+        parent::__construct($pointer);
+    }
+
+    /**
+     * Make a new source from a file descriptor (a small integer).
+     * Make a new source that is attached to the descriptor. For example:
+     *      $source = VipsSource::newFromDescriptor(0)
+     * Makes a descriptor attached to stdin.
+     * You can pass this source to (for example) @see Image::newFromSource()
+     * @throws Exception
+     */
+    public static function newFromDescriptor(int $descriptor): self
+    {
+        $pointer = FFI::vips()->vips_source_new_from_descriptor($descriptor);
+
+        if ($pointer === null) {
+            throw new Exception("can't create source from descriptor $descriptor");
+        }
+
+        return new self($pointer);
+    }
+
+    /**
+     * Make a new source from a filename.
+     * Make a new source that is attached to the named file. For example:
+     *      $source = VipsSource::newFromFile("myfile.jpg")
+     * You can pass this source to (for example) @see Image::newFromSource()
+     * @throws Exception
+     */
+    public static function newFromFile(string $filename): self
+    {
+        $pointer = FFI::vips()->vips_source_new_from_file($filename);
+
+        if ($pointer === null) {
+            throw new Exception("can't create source from filename $filename");
+        }
+
+        return new self($pointer);
+    }
+
+    /**
+     * Make a new source from a filename.
+     * Make a new source that uses the provided $data. For example:
+     *      $source = VipsSource::newFromFile(file_get_contents("myfile.jpg"))
+     * You can pass this source to (for example) @see Image::newFromSource()
+     * @throws Exception
+     */
+    public static function newFromMemory(string $data): self
+    {
+        # we need to set the memory to a copy of the data that vips_lib
+        # can own and free
+        $n = strlen($data);
+        $memory = \FFI::new("char[$n]", false, true);
+        \FFI::memcpy($memory, $data, $n);
+        $pointer = FFI::vips()->vips_source_new_from_memory($memory, $n);
+
+        if ($pointer === null) {
+            throw new Exception("can't create source from memory");
+        }
+
+        return new self($pointer);
+    }
+}
diff --git a/src/SourceCustom.php b/src/SourceCustom.php
new file mode 100644
index 0000000..47d9bb4
--- /dev/null
+++ b/src/SourceCustom.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace Jcupitt\Vips;
+
+class SourceCustom extends Source
+{
+    /**
+     * A pointer to the underlying VipsSourceCustom. This is the same as the
+     * GObject, just cast to VipsSourceCustom to help FFI.
+     *
+     * @internal
+     */
+    public \FFI\CData $pointer;
+
+    public function __construct()
+    {
+        $this->pointer = FFI::vips()->vips_source_custom_new();
+        parent::__construct($this->pointer);
+    }
+
+    /**
+     * Attach a read handler.
+     * The interface is similar to fread. The handler is given a number
+     * of bytes to fetch, and should return a bytes-like object containing up
+     * to that number of bytes. If there is no more data available, it should
+     * return null.
+     */
+    public function onRead(callable $callback): void
+    {
+        $this->signalConnect('read', $callback);
+    }
+
+    /**
+     * Attach a seek handler.
+     * The interface is the same as fseek, so the handler is passed
+     * parameters for $offset and $whence with the same meanings.
+     * However, the handler MUST return the new seek position. A simple way
+     * to do this is to call ftell() and return that result.
+     * Seek handlers are optional. If you do not set one, your source will be
+     * treated as unseekable and libvips will do extra caching.
+     * $whence in particular:
+     *  0 => start
+     *  1 => current position
+     *  2 => end
+     */
+    public function onSeek(callable $callback): void
+    {
+        $this->signalConnect('seek', $callback);
+    }
+}
diff --git a/src/SourceResource.php b/src/SourceResource.php
new file mode 100644
index 0000000..9eaefdd
--- /dev/null
+++ b/src/SourceResource.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Jcupitt\Vips;
+
+class SourceResource extends SourceCustom
+{
+    /**
+     * @var resource
+     */
+    private $resource;
+
+    /**
+     * The resource passed in will become "owned" by this class.
+     * On destruction of this class, the resource will be closed.
+     *
+     * @param resource $resource
+     */
+    public function __construct($resource)
+    {
+        $this->resource = $resource;
+        parent::__construct();
+
+        $this->onRead(static function (int $length) use (&$resource): ?string {
+            return fread($resource, $length) ?: null;
+        });
+
+        if (stream_get_meta_data($resource)['seekable']) {
+            $this->onSeek(static function (int $offset, int $whence) use (&$resource): int {
+                fseek($resource, $offset, $whence);
+                return ftell($resource);
+            });
+        }
+    }
+
+    public function __destruct()
+    {
+        fclose($this->resource);
+        parent::__destruct();
+    }
+}
diff --git a/src/Target.php b/src/Target.php
new file mode 100644
index 0000000..9b31e61
--- /dev/null
+++ b/src/Target.php
@@ -0,0 +1,74 @@
+<?php
+
+namespace Jcupitt\Vips;
+
+class Target extends Connection
+{
+    /**
+     * A pointer to the underlying VipsTarget. This is the same as the
+     * GObject, just cast to VipsTarget to help FFI.
+     *
+     * @internal
+     */
+    public \FFI\CData $pointer;
+
+    public function __construct(\FFI\CData $pointer)
+    {
+        $this->pointer = \FFI::cast(FFI::ctypes('VipsTarget'), $pointer);
+        parent::__construct($pointer);
+    }
+
+    /**
+     * Make a new target to write to a file descriptor (a small integer).
+     * Make a new target that is attached to the descriptor. For example::
+     *      $target = VipsTarget.newToDescriptor(1)
+     * Makes a descriptor attached to stdout.
+     * You can pass this target to (for example) @see Image::writeToTarget()
+     * @throws Exception
+     */
+    public static function newToDescriptor(int $descriptor): self
+    {
+        $pointer = FFI::vips()->vips_target_new_to_descriptor($descriptor);
+        if ($pointer === null) {
+            throw new Exception("can't create output target from descriptor $descriptor");
+        }
+
+        return new self($pointer);
+    }
+
+    /**
+     * Make a new target to write to a file name.
+     * Make a new target that is attached to the file name. For example::
+     *      $target = VipsTarget.newToFile("myfile.jpg")
+     * You can pass this target to (for example) @see Image::writeToTarget()
+     * @throws Exception
+     */
+    public static function newToFile(string $filename): self
+    {
+        $pointer = FFI::vips()->vips_target_new_to_file($filename);
+
+        if ($pointer === null) {
+            throw new Exception("can't create output target from filename $filename");
+        }
+
+        return new self($pointer);
+    }
+
+    /**
+     * Make a new target to write to a memory buffer.
+     * For example::
+     *      $target = VipsTarget.newToMemory()
+     * You can pass this target to (for example) @see Image::writeToTarget()
+     * @throws Exception
+     */
+    public static function newToMemory(): self
+    {
+        $pointer = FFI::vips()->vips_target_new_to_memory();
+
+        if ($pointer === null) {
+            throw new Exception("can't create output target from memory");
+        }
+
+        return new self($pointer);
+    }
+}
diff --git a/src/TargetCustom.php b/src/TargetCustom.php
new file mode 100644
index 0000000..dedb149
--- /dev/null
+++ b/src/TargetCustom.php
@@ -0,0 +1,94 @@
+<?php
+
+namespace Jcupitt\Vips;
+
+class TargetCustom extends Target
+{
+    /**
+     * A pointer to the underlying VipsTargetCustom. This is the same as the
+     * GObject, just cast to VipsTargetCustom to help FFI.
+     *
+     * @internal
+     */
+    public \FFI\CData $pointer;
+
+    public function __construct()
+    {
+        $this->pointer = FFI::vips()->vips_target_custom_new();
+        parent::__construct($this->pointer);
+    }
+
+    /**
+     * Attach a write handler.
+     * The interface is exactly as fwrite. The handler is given a bytes-like object to write,
+     * and should return the number of bytes written.
+     * @throws Exception
+     */
+    public function onWrite(callable $callback): void
+    {
+        $this->signalConnect('write', $callback);
+    }
+
+    /**
+     * Attach a read handler.
+     * The interface is similar to fread. The handler is given a number
+     * of bytes to fetch, and should return a bytes-like object containing up
+     * to that number of bytes. If there is no more data available, it should
+     * return null.
+     * Read handlers on VipsTarget are optional. If you do not set one, your
+     * target will be treated as unreadable and libvips will be unable to
+     * write some file types (just TIFF, as of the time of writing).
+     */
+    public function onRead(callable $callback): void
+    {
+        if (FFI::atLeast(8, 13)) {
+            $this->signalConnect('read', $callback);
+        }
+    }
+
+    /**
+     * Attach a seek handler.
+     * The interface is the same as fseek, so the handler is passed
+     * parameters for $offset and $whence with the same meanings.
+     * However, the handler MUST return the new seek position. A simple way
+     * to do this is to call ftell() and return that result.
+     * Seek handlers are optional. If you do not set one, your source will be
+     * treated as unseekable and libvips will do extra caching.
+     * $whence in particular:
+     *  0 => start
+     *  1 => current position
+     *  2 => end
+     */
+    public function onSeek(callable $callback): void
+    {
+        if (FFI::atLeast(8, 13)) {
+            $this->signalConnect('seek', $callback);
+        }
+    }
+
+    /**
+     * Attach an end handler.
+     * This optional handler is called at the end of write. It should do any
+     * cleaning up necessary, and return 0 on success and -1 on error.
+     * Automatically falls back to onFinish if libvips <8.13
+     * @throws Exception
+     */
+    public function onEnd(callable $callback): void
+    {
+        if (FFI::atLeast(8, 13)) {
+            $this->signalConnect('end', $callback);
+        } else {
+            $this->onFinish($callback);
+        }
+    }
+
+    /**
+     * Attach a finish handler.
+     * For libvips 8.13 and later, this method is deprecated in favour of @throws Exception
+     * @see TargetCustom::onEnd()
+     */
+    public function onFinish(callable $callback): void
+    {
+        $this->signalConnect('finish', $callback);
+    }
+}
diff --git a/src/TargetResource.php b/src/TargetResource.php
new file mode 100644
index 0000000..b8e90a6
--- /dev/null
+++ b/src/TargetResource.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace Jcupitt\Vips;
+
+class TargetResource extends TargetCustom
+{
+    /**
+     * @var resource
+     */
+    private $resource;
+
+    /**
+     * The resource passed in will become "owned" by this class.
+     * On destruction of this class, the resource will be closed.
+     *
+     * @param resource $resource
+     */
+    public function __construct($resource)
+    {
+        $this->resource = $resource;
+        parent::__construct();
+
+        $this->onWrite(static function (string $buffer) use (&$resource): int {
+            return fwrite($resource, $buffer) ?: 0;
+        });
+
+        $this->onEnd(static function () use (&$resource): void {
+            fclose($resource);
+        });
+
+        $meta = stream_get_meta_data($resource);
+        // See: https://www.php.net/manual/en/function.fopen.php
+        if (substr($meta['mode'], -1) === '+') {
+            $this->onRead(static function (int $length) use (&$resource): ?string {
+                return fread($resource, $length) ?: null;
+            });
+        }
+
+        if ($meta['seekable']) {
+            $this->onSeek(static function (int $offset, int $whence) use (&$resource): int {
+                fseek($resource, $offset, $whence);
+                return ftell($resource);
+            });
+        }
+    }
+
+    public function __destruct()
+    {
+        if (is_resource($this->resource)) {
+            fclose($this->resource);
+        }
+        parent::__destruct();
+    }
+}
diff --git a/tests/StreamingTest.php b/tests/StreamingTest.php
new file mode 100644
index 0000000..9d07184
--- /dev/null
+++ b/tests/StreamingTest.php
@@ -0,0 +1,99 @@
+<?php
+
+namespace Jcupitt\Vips\Test;
+
+use Generator;
+use Jcupitt\Vips\Exception;
+use Jcupitt\Vips\Image;
+use Jcupitt\Vips\Source;
+use Jcupitt\Vips\SourceResource;
+use Jcupitt\Vips\Target;
+use Jcupitt\Vips\TargetResource;
+use PHPUnit\Framework\TestCase;
+
+class StreamingTest extends TestCase
+{
+    /**
+     * @throws Exception
+     */
+    public function sourceAndTargetProvider(): Generator
+    {
+        $sources = [
+            'File' => fn() => Source::newFromFile(__DIR__ . '/images/img_0076.jpg'),
+            'Memory' => fn() => Source::newFromMemory(file_get_contents(__DIR__ . '/images/img_0076.jpg')),
+            'Resource' => fn() => new SourceResource(fopen(__DIR__ . '/images/img_0076.jpg', 'rb'))
+        ];
+        $targets = [
+            'File' => fn() => Target::newToFile(tempnam(sys_get_temp_dir(), 'image')),
+            'Memory' => fn() => Target::newToMemory(),
+            'Resource' => fn() => new TargetResource(fopen('php://memory', 'wb+')),
+            'Resource(Not Readable)' => fn() => new TargetResource(fopen('php://memory', 'wb'))
+        ];
+
+        foreach ($sources as $sourceName => $source) {
+            foreach ($targets as $targetName => $target) {
+                yield "$sourceName => $targetName" => [$source(), $target()];
+            }
+        }
+    }
+
+    /**
+     * @dataProvider sourceAndTargetProvider
+     */
+    public function testFromSourceToTarget(Source $source, Target $target): void
+    {
+        $image = Image::newFromSource($source);
+        $image->writeToTarget($target, '.jpg[Q=95]');
+
+        // Try delete temporary file
+        if ($target->filename() !== null) {
+            @unlink($target->filename());
+        }
+    }
+
+    /**
+     * This test case is extra since it's the easiest to make sure we can "reload" the saved image
+     */
+    public function testFromFileToFile(): void
+    {
+        $source = Source::newFromFile(__DIR__ . '/images/img_0076.jpg');
+        $target = Target::newToFile(tempnam(sys_get_temp_dir(), 'image'));
+        $image = Image::newFromSource($source);
+        $image->writeToTarget($target, '.jpg[Q=95]');
+
+        // Make sure we can load the file
+        $image = Image::newFromFile($target->filename());
+        $image->writeToBuffer('.jpg[Q=95]');
+        unlink($target->filename());
+    }
+
+    public function testNoLeak(): void
+    {
+        $lastUsage = 0;
+        $leaked = false;
+        for ($i = 0; $i < 10; $i++) {
+            $filename = tempnam(sys_get_temp_dir(), 'image');
+            $source = new SourceResource(fopen(__DIR__ . '/images/img_0076.jpg', 'rb'));
+            $target = new TargetResource(fopen($filename, 'wb+'));
+            $image = Image::newFromSource($source);
+            $image->writeToTarget($target, '.jpg[Q=95]');
+            unlink($filename);
+            $usage = memory_get_peak_usage(true);
+            $diff = $usage - $lastUsage;
+            if ($lastUsage !== 0 && $diff > 0) {
+                $leaked = true;
+            }
+            $lastUsage = $usage;
+        }
+
+        $this->assertFalse($leaked, 'Streaming leaked memory');
+    }
+
+    public function testFromFileToDescriptor(): void
+    {
+        // NOTE(L3tum): There is no way to get a file descriptor in PHP :)
+        // In theory we could use the known fds like stdin or stdout,
+        // but that would spam those channels full with an entire image file.
+        // Because of that I've chosen to omit this test.
+    }
+}