Corrupted PNG files

[watchingdogs]

After extracting a pack (with GUI) I successfully got the directory of the pack, and I was able to view random images. However, when I tried to load it with Python's PIL library, I found that the images have CRC errors.

Example pngcheck output:

 chunk IHDR at offset 0x0000c, length 13
    256 x 256 image, 24-bit RGB, non-interlaced
  CRC error in chunk IHDR (computed d3103f31, expected d8928bab)

While the image data might be there, this mismatch causes many programs to identify the files as corrupted, and thus do not allow any further use.

[watchingdogs]

This wasn't the only issue, the file was broken in many other ways, so I had to re-encode them. The exact steps I took were

• Generating entirely new PNG chunk structures
• Calculating correct CRC-32 checksums for all chunks
• Creating properly compressed IDAT chunks with valid zlib streams
• Writing a compliant PNG file from scratch (with PIL in my case, I do not know java)

Would be nice if everyone had working images.