[squeak-dev] PNGReadWriter buglet

tim Rowledge tim at rowledge.org
Sun Feb 26 00:33:11 UTC 2023

> On 2023-02-25, at 3:46 PM, Vanessa Freudenberg <vanessa at codefrau.net> wrote:
> On further testing:

Some more info

A png that loads nicely has an IHDR chunk, and IDAT chunk and an IEND.

A CCTV png that looks crummy has an unrecognised sRGB chunk (we keep a list in PNGReadWriter>>#processNextChunk and I de-commented the Transcript show of the list in PNGReadWriter>>#nextImage)

A sample png (http://www.libpng.org/pub/png/img_png/pass7_sml.png) really does some oddness
- in a 5.3 image it displays without the R+G channels in the FileList preview but is fine if opened as a SketchMorph
- in a trunk image it displays perfectly well in both cases 
- but it has an unrecognised tEXt chunk

Both the tExt & sRGB are legitimate according to the standard but I doubt this can be the source of my current problem if an old 2.8 image can load the image properly.

tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
If you think C++ is not overly complicated, just what is a protected abstract virtual base pure virtual private destructor and when was the last time you needed one? -- Tom Cargin

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