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Fix alpha encoding in extended-range PNG snapshots - #281
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@pixelmatrix thanks a lot for raising this! I'm looking into adopting your general strategy via #284 and make a few minor tweaks. Out of curiosity, have you filed a feedback for this by chance? It seems quite surprising to me that the "deafult" PNG encoding path would apparently lose color/alpha info like this, so feels like something that should be fixed in the frameworks. Edit: For the record, I filed FB25109021 and opened this dev forum thread to see if this can be addressed at a framework level. |
jamieQ
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Preserve UIImage orientation metadata when exporting through ImageIO. Use small color-aware regression fixtures and a strict expected-failure check to flag a future UIKit alpha fix. Refs #281
jamieQ
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* Fix alpha encoding in extended-range PNG snapshots * fix(png): Preserve orientation and strengthen encoding coverage Preserve UIImage orientation metadata when exporting through ImageIO. Use small color-aware regression fixtures and a strict expected-failure check to flag a future UIKit alpha fix. Refs #281 * test(png): Simplify UIKit alpha canary assertions * test(png): Simplify image encoding regression checks Compare decoded pixels with the source image instead of parsing 16-bit PNG samples. * test(png): Check orientation independently of UIKit metadata --------- Co-authored-by: Josh Pyles <josh@linear.app>
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Closing in favor of #284. Version |
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We were seeing artifacts on partially transparent pixels in our snapshot tests, and after some research, found that
UIImage.pngData()causes this reliably. Exporting using ImageIO does not have the same problem. I've forked this and implemented a fix for us, and wanted to contribute it back, in case it's useful.