[squeak-dev] PNGReadWriter buglet

tim Rowledge tim at rowledge.org
Sat Feb 25 23:37:30 UTC 2023

> 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 Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
Useful Latin Phrases:- Mellita, domi adsum. = Honey, I'm home.

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