On further testing:

up to 4.4: fine
https://squeak.js.org/run/#zip=https://files.squeak.org/4.4/Squeak4.4-12327.zip

since 4.5: broken
https://squeak.js.org/run/#zip=https://files.squeak.org/4.5/Squeak4.5-13680.zip

Filing 4.4's PNGReadWriter into 4.5 fixes the yellowing issue.

Just filing in 4.4's PNGReadWriter>>copyPixelsRGB: also fixes the yellowing
issue.

Attaching ...

(I realize this may be entirely unrelated to the issue you are seeing)

Vanessa

On Sat, Feb 25, 2023 at 3:37 PM tim Rowledge <tim at rowledge.org> wrote:

>
>
> > On 2023-02-25, at 2:41 PM, Vanessa Freudenberg <vanessa at codefrau.net>
> wrote:
> >
> > Ohhh would you look at that ... works perfectly in a 2.8 image:
>
>
> Oh, right, so we've now written advanced new technology bugs. Lovely!
> These problem files are from CCTV cameras so who knows how well they obey
> any standards.
>
> The current PNGReadWriter has a debug output to the Transcript that tells
> me the image has -
> form = Form(252x172x32)
> colorType = 2
> interlaceMethod = 1
> filters = {137->1 . 129->3 . 54->2 . 3->4}
>
> whereas all the PNG's I can find that load 'properly' seem to have
> colorType = 6, interlace method = 0 and a bit oddly, appear to repeat the
> debug output as if it is processed twice? Hmm, shomething wrong offisher?
> Still, a different interlace code might be a good clue given the image
> actually *looks* like interlace-screwed.
>
> Oh, so much for that theory, I found a demo png with colorType = 3 and
> interlace 1. Poo.
>
> tim
> --
> tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
> Useful Latin Phrases:- Mellita, domi adsum. = Honey, I'm home.
>
>
>
>
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