[#67 state:fixed] Fixed block.pyx so it takes Qt pixel alignment into account.

--HG--
extra : convert_revision : svn%3Ac306627e-7827-47d3-bdf0-9a457c9553a1/trunk%40172

pe/qt/modules/block/block.pyx

@@ -6,7 +6,7 @@
 # http://www.hardcoded.net/licenses/hs_license
 
 cdef object getblock(object image):
-    cdef int width, height, pixel_count, red, green, blue, i, offset
+    cdef int width, height, pixel_count, red, green, blue, i, offset, bytes_per_line
     cdef char *s
     cdef unsigned char r, g, b
     width = image.width()
@@ -14,16 +14,21 @@ cdef object getblock(object image):
     if width:
         pixel_count = width * height
         red = green = blue = 0
+        bytes_per_line = image.bytesPerLine()
         tmp = image.bits().asstring(image.numBytes())
         s = tmp
-        for i in range(pixel_count):
-            offset = i * 3
-            r = s[offset]
-            g = s[offset + 1]
-            b = s[offset + 2]
-            red += r
-            green += g
-            blue += b
+        # Qt aligns all its lines on 32bit, which means that if the number of bytes per
+        # line for image is not divisible by 4, there's going to be crap inserted in "s"
+        # We have to take this into account when calculating offsets
+        for i in range(height):
+            for j in range(width):
+                offset = i * bytes_per_line + j * 3
+                r = s[offset]
+                g = s[offset + 1]
+                b = s[offset + 2]
+                red += r
+                green += g
+                blue += b
         return (red // pixel_count, green // pixel_count, blue // pixel_count)
     else:
         return (0, 0, 0)
@@ -38,9 +43,9 @@ def getblocks(image, int block_count_per_side):
     block_height = max(height // block_count_per_side, 1)
     result = []
     for ih in range(block_count_per_side):
-        top = min(ih * block_height, height - block_height)
+        top = min(ih*block_height, height-block_height-1)
         for iw in range(block_count_per_side):
-            left = min(iw * block_width, width - block_width)
+            left = min(iw*block_width, width-block_width-1)
             crop = image.copy(left, top, block_width, block_height)
             result.append(getblock(crop))
     return result