[FFmpeg-trac] #6381(avcodec:new): Re-encoding png image fails

[FFmpeg]

#6381: Re-encoding png image fails
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             Reporter:  guest123    |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avcodec
              Version:  git-master  |               Resolution:
             Keywords:  png         |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Comment (by guest123):

 `Which did you test?` I tested it with a lot of image viewers/editors on
 windows. All modern browsers can display that image (Chrome, Mozilla,
 Safari, Opera, IE, etc), you can edit it in Paint, open and edit it with
 ACDSee Image Viewer, Mirilic Action Image Viewer, Panorama Maker, Image
 Resizer etc. All of them opens image without anywarnings or errors.

 `Why do you believe this is a valid png file?` Actually, this is not
 completely valid png file. One of IDAT chunks has unconsistent CRC32 hash,
 which means that the file may be corrupted. But, I tested some images with
 bad CRC32 hashes and Ffmpeg converts them without errors. Also, in this
 image IEND chunk is missing, and also a few IDAT chunks at the ends.
 Shouldn't Ffmpeg just fill that part of image with transparent or black
 pixel data (like all other image editors do)?

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Ticket URL: <https://trac.ffmpeg.org/ticket/6381#comment:2>
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