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  Saving alpha-0 pixels via ImageIO  (Read 1584 times)
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Offline Orangy Tang

JGO Kernel

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Monkey for a head

« Posted 2012-04-19 14:16:08 »

Here's an odd one - saving a png via ImageIO seems to have a 'cute' optimisation where all alpha=0 pixels have their rgb values set to 0 as well. Presumably to try and make non-visible pixels compress better.

However I'm just using pngs as a handy way of storting 4 channels of pixel data, so this optimisation throws away some of my data. Sad Has anyone else bumped into this issue before as well? How did you fix it?

* Orangy Tang goes looking for alternate png encoders...

[ - Play Growth Spurt, Rescue Squad and Snowman Village ] [ Rebirth - game resource library ]
Offline princec

« JGO Spiffy Duke »

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« Reply #1 - Posted 2012-04-19 14:58:05 »

Nice optimisation but incredibly useless unless you've got premultiplied alpha! If you're just using pngs to store 4-channel data I'd suggest instead using raw data and gzipping the data yourself, because that's pretty much all pngs do. In other words custom file format ftw.

Cas Smiley

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