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Failure to detect incorrect CRC in PNG?

  • Attached ZIP contains two 32x32 PNG files (downloaded on the web for testing purposes specifically); both are with incorrect CRC in one of the chunks.

    (1) Invalid_CRC_xcsn0g01.png (PNG ColorType 0, BitDepth 1)
    (2) Invalid_CRC_xhdn0g08.png (PNG ColorType 0, BitDepth 8)

    "1" coded CRC for IDAT as "4353554d" when it should be "d02f14c9"
    "2" coded CRC for IHDR as "4353554d" when it should be "56112528"

    FreeImage correctly rejected "2", but accepted "1". Would it be a failure in detecting the incorrect CRC here?

    Please don't try to load the above PNG with GDIplus, as GDIplus appears to just ignore CRC verification all the time, even with the newer version on Win 7.

    Last edit: Johnny Petersen 2013-08-12