MSS: fix errors from pngcheck tool

BoboTiG · BoboTiG · commit b2d88150395c · 2015-05-04T16:30:56.000+02:00
diff --git a/doc/CHANGELOG b/doc/CHANGELOG
@@ -8,6 +8,7 @@ devel   201y/mm/dd
       - prevent export of MSS* classes in case of "from mss import *"
       - MSS: rename save_img() to to_png()
       - MSS: optimization of to_png()
+      - MSS: to_png() generate valid PNG files
       - MSSLinux: prevent segfault when DISPLAY is set but no X server started
       - MSSLinux: get_pixels() insanely fast, use of MSS library (C code)
       - MSSWindows: get_pixels() insanely fast
diff --git a/doc/QUALITY b/doc/QUALITY
@@ -12,3 +12,6 @@ codespell doc/*
 
 # Dry run
 python setup.py check
+
+# Check generated PNG
+pngcheck -c *.png
diff --git a/mss.py b/mss.py
@@ -204,16 +204,21 @@ def to_png(self, data, width, height, output):
             ihdr[2] = b(b'>2I5B', width, height, 8, 2, 0, 0, 0)
             ihdr[3] = b(b'>I', crc32(b''.join(ihdr[1:3])) & 0xffffffff)
             ihdr[0] = b(b'>I', len(ihdr[2]))
+            ihdr = b''.join(ihdr)
 
             # Data: size, marker, data, CRC32
             idat = [b'', b'IDAT', compress(scanlines), b'']
             idat[3] = b(b'>I', crc32(b''.join(idat[1:3])) & 0xffffffff)
             idat[0] = b(b'>I', len(idat[2]))
+            idat = b''.join(idat)
 
             # Footer: size, marker, None, CRC32
-            iend = b'4IEND'
+            iend = [b'', b'IEND', b'', b'']
+            iend[3] = b(b'>I', crc32(b''.join(iend[1:3])) & 0xffffffff)
+            iend[0] = b(b'>I', len(iend[2]))
+            iend = b''.join(iend)
 
-            fileh.write(magic + b''.join(ihdr) + b''.join(idat) + iend)
+            fileh.write(magic + ihdr + idat + iend)
             return
 
         err = 'MSS: error writing data to "{0}".'.format(output)
