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webgl-2d-image-3x3-convolution-with-loop.html
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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL2 - 2D image 3x3 convolution with loop</title>
<link type="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
</head>
<body>
<canvas id="canvas" width="400" height="300"></canvas>
<div id="uiContainer">
<div id="ui"></div>
</div>
</body>
<script src="resources/webgl-utils.js"></script>
<script src="resources/webgl-lessons-helper.js"></script>
<script>
"use strict";
var vertexShaderSource = `#version 300 es
// an attribute is an input (in) to a vertex shader.
// It will receive data from a buffer
in vec2 a_position;
in vec2 a_texCoord;
// Used to pass in the resolution of the canvas
uniform vec2 u_resolution;
// Used to pass the texture coordinates to the fragment shader
out vec2 v_texCoord;
// all shaders have a main function
void main() {
// convert the position from pixels to 0.0 to 1.0
vec2 zeroToOne = a_position / u_resolution;
// convert from 0->1 to 0->2
vec2 zeroToTwo = zeroToOne * 2.0;
// convert from 0->2 to -1->+1 (clipspace)
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
// pass the texCoord to the fragment shader
// The GPU will interpolate this value between points.
v_texCoord = a_texCoord;
}
`;
var fragmentShaderSource = `#version 300 es
// fragment shaders don't have a default precision so we need
// to pick one. mediump is a good default. It means "medium precision"
precision mediump float;
// our texture
uniform sampler2D u_image;
// the convolution kernal data
uniform float u_kernel[9];
uniform float u_kernelWeight;
// the texCoords passed in from the vertex shader.
in vec2 v_texCoord;
// we need to declare an output for the fragment shader
out vec4 outColor;
void main() {
vec2 onePixel = vec2(1) / vec2(textureSize(u_image, 0));
vec4 colorSum =
texture(u_image, v_texCoord + onePixel * vec2(-1, -1)) * u_kernel[0] +
texture(u_image, v_texCoord + onePixel * vec2( 0, -1)) * u_kernel[1] +
texture(u_image, v_texCoord + onePixel * vec2( 1, -1)) * u_kernel[2] +
texture(u_image, v_texCoord + onePixel * vec2(-1, 0)) * u_kernel[3] +
texture(u_image, v_texCoord + onePixel * vec2( 0, 0)) * u_kernel[4] +
texture(u_image, v_texCoord + onePixel * vec2( 1, 0)) * u_kernel[5] +
texture(u_image, v_texCoord + onePixel * vec2(-1, 1)) * u_kernel[6] +
texture(u_image, v_texCoord + onePixel * vec2( 0, 1)) * u_kernel[7] +
texture(u_image, v_texCoord + onePixel * vec2( 1, 1)) * u_kernel[8] ;
outColor = vec4((colorSum / u_kernelWeight).rgb, 1);
}
`;
var image = new Image();
image.src = "resources/leaves.jpg"; // MUST BE SAME DOMAIN!!!
image.onload = function() {
render(image);
}
function render(image) {
// Get A WebGL context
var canvas = document.getElementById("canvas");
webglLessonsHelper.setupLesson(canvas);
/** @type {WebGLRenderingContext} */
var gl = canvas.getContext("webgl2");
if (!gl) {
webglLessonsHelper.showNeedWebGL2(canvas);
return;
}
// setup GLSL program
var program = webglUtils.createProgramFromSources(gl,
[vertexShaderSource, fragmentShaderSource]);
// look up where the vertex data needs to go.
var positionAttributeLocation = gl.getAttribLocation(program, "a_position");
var texCoordAttributeLocation = gl.getAttribLocation(program, "a_texCoord");
// lookup uniforms
var resolutionLocation = gl.getUniformLocation(program, "u_resolution");
var imageLocation = gl.getUniformLocation(program, "u_image");
var kernelLocation = gl.getUniformLocation(program, "u_kernel[0]");
var kernelWeightLocation = gl.getUniformLocation(program, "u_kernelWeight");
// Create a vertex array object (attribute state)
var vao = gl.createVertexArray();
// and make it the one we're currently working with
gl.bindVertexArray(vao);
// Create a buffer and put a single pixel space rectangle in
// it (2 triangles)
var positionBuffer = gl.createBuffer();
// Turn on the attribute
gl.enableVertexAttribArray(positionAttributeLocation);
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionAttributeLocation, size, type, normalize, stride, offset)
// provide texture coordinates for the rectangle.
var texCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texCoordBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
0.0, 0.0,
1.0, 0.0,
0.0, 1.0,
0.0, 1.0,
1.0, 0.0,
1.0, 1.0]), gl.STATIC_DRAW);
gl.enableVertexAttribArray(texCoordAttributeLocation);
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
texCoordAttributeLocation, size, type, normalize, stride, offset)
// Pass in the canvas resolution so we can convert from
// pixels to clipspace in the shader
gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);
var kernels = {
normal: [0, 0, 0, 0, 1, 0, 0, 0, 0],
gaussianBlur: [0.045, 0.122, 0.045, 0.122,
0.332, 0.122, 0.045, 0.122, 0.045],
gaussianBlur2: [1, 2, 1, 2, 4, 2, 1, 2, 1],
gaussianBlur3: [0, 1, 0, 1, 1, 1, 0, 1, 0],
unsharpen: [-1, -1, -1, -1, 9, -1, -1, -1, -1],
sharpness: [0,-1,0,-1,5,-1,0,-1,0],
sharpen: [-1, -1, -1, -1, 16, -1, -1, -1, -1],
edgeDetect: [-0.125, -0.125, -0.125, -0.125,
1, -0.125, -0.125, -0.125, -0.125],
edgeDetect2: [-1, -1, -1, -1, 8, -1, -1, -1, -1],
edgeDetect3: [-5, 0, 0, 0, 0, 0, 0, 0, 5],
edgeDetect4: [-1, -1, -1, 0, 0, 0, 1, 1, 1],
edgeDetect5: [-1, -1, -1, 2, 2, 2, -1, -1, -1],
edgeDetect6: [-5, -5, -5, -5, 39, -5, -5, -5, -5],
sobelHorizontal: [1, 2, 1, 0, 0, 0, -1, -2, -1 ],
sobelVertical: [1, 0, -1, 2, 0, -2, 1, 0, -1 ],
previtHorizontal: [1, 1, 1, 0, 0, 0, -1, -1, -1 ],
previtVertical: [1, 0, -1, 1, 0, -1, 1, 0, -1],
boxBlur: [0.111, 0.111, 0.111, 0.111,
0.111, 0.111, 0.111, 0.111, 0.111],
triangleBlur: [ 0.0625, 0.125, 0.0625,
0.125, 0.25, 0.125, 0.0625, 0.125, 0.0625]
};
// Setup UI to pick kernels.
var ui = document.getElementById("ui");
for (var name in kernels) {
var input = document.createElement("input");
input.type = "radio";
input.name = "kernel";
input.value = name;
if (name == 'edgeDetect') {
input.checked = "checked";
}
ui.appendChild(input);
ui.appendChild(document.createTextNode(name));
ui.appendChild(document.createElement("br"));
input.onclick = function(name) {
return function() {
drawWithKernel(name);
}
}(name);
}
// Create a buffer and put a single clipspace rectangle in
// it (2 triangles)
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
setRectangle( gl, 0, 0, image.width, image.height);
drawWithKernel('edgeDetect');
function computeKernelWeight(kernel) {
var weight = kernel.reduce(function(prev, curr) {
return prev + curr;
});
return weight <= 0 ? 1 : weight;
}
function drawWithKernel(name) {
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Clear the canvas
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// Bind the attribute/buffer set we want.
gl.bindVertexArray(vao);
// Pass in the canvas resolution so we can convert from
// pixels to clipspace in the shader
gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);
// Tell the shader to get the texture from texture unit 0
gl.uniform1i(imageLocation, 0);
// set the kernel and it's weight
gl.uniform1fv(kernelLocation, kernels[name]);
gl.uniform1f(kernelWeightLocation, computeKernelWeight(kernels[name]));
// Draw the rectangle.
var primitiveType = gl.TRIANGLES;
var offset = 0;
var count = 6;
gl.drawArrays(primitiveType, offset, count);
}
}
function randomInt(range) {
return Math.floor(Math.random() * range);
}
function setRectangle(gl, x, y, width, height) {
var x1 = x;
var x2 = x + width;
var y1 = y;
var y2 = y + height;
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
x1, y1,
x2, y1,
x1, y2,
x1, y2,
x2, y1,
x2, y2]), gl.STATIC_DRAW);
}
</script>
</html>