solved 28

Author: JavaProgrammerLB

Diff for: 28.py

@@ -0,0 +1,38 @@
+import download_file
+
+from PIL import Image
+
+
+def main():
+    url = "http://www.pythonchallenge.com/pc/ring/bell.png"
+    file_path = "ring/bell.png"
+    username = "repeat"
+    password = "switch"
+    # first_step(url, file_path, username, password)
+    second_step(file_path)
+
+
+def first_step(url, file_path, username, password):
+    download_file.download_with_auth(url, file_path, username, password)
+
+
+def second_step(file_path):
+    im = Image.open(file_path)
+    green_channel = 1
+    green_data = im.getdata(green_channel)
+    datas = list(green_data)
+    datas_len = len(datas)
+    assert datas_len % 2 == 0
+    message = ""
+    for i in range(int(datas_len / 2)):
+        index = 2 * i
+        left = datas[index]
+        right = datas[index + 1]
+        abs_left_min_right = abs(left - right)
+        if abs_left_min_right != 42:
+            message += chr(abs_left_min_right)
+    print(message)
+
+
+if __name__ == "__main__":
+    main()

Diff for: README.md

@@ -1,6 +1,14 @@
 # pythonchallenge
 Solve Problems in http://www.pythonchallenge.com
 
+#### 28
+result: http://www.pythonchallenge.com/pc/ring/guido.html 
+- use image.split() to split RGB channels
+- im.bands() return number of im's channels
+- ring means "green" if you visit "green.html" will get response "yes"
+- whodunnit is an word means "who is the murderer"
+ 
+
 #### 27 
 result: http://www.pythonchallenge.com/pc/ring/bell.html auth=(repeat, switch)
 - author use python2 keyword, but there is some different with python3