NotMyFault Posted May 31, 2023 Posted May 31, 2023 Hi, when I try to convert the document from RGB/16 to RGB/8, black spots will be created in the right-middle area. Best observable when using Chanels panel and choosing only one color channel. The images show green channel. Image 1: RGB/16 (looks ok) Image 2: RGB/8 (black pixels are wrong) Image 3: Conversion alpha channel packing.afphoto Quote Mac mini M1 A2348 | Windows 10 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080 LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 iPad Air Gen 5 (2022) A2589 Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps. My posts focus on technical aspects and leave out most of social grease like „maybe“, „in my opinion“, „I might be wrong“ etc. just add copy/paste all these softeners from this signature to make reading more comfortable for you. Otherwise I’m a fine person which respects you and everyone and wants to be respected.
NotMyFault Posted May 31, 2023 Author Posted May 31, 2023 The issue is probably caused by the alpha channel which is almost zero in that area. the loss of the lower 8 bit causes an unexpected effect. I would expect that the color channels and alpha get converted individually. It seems that the least significant bit get rounded randomly to 0 or 1, so the color channels get erased where alpha gets zero. The "all 8 bit colors" was generated with help of PT filters (so no dithering has happened there), then I added a rectangle with conical gradient on alpha (which may create the unwanted dithering, even if color is pure white at all nodes). Quote Mac mini M1 A2348 | Windows 10 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080 LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 iPad Air Gen 5 (2022) A2589 Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps. My posts focus on technical aspects and leave out most of social grease like „maybe“, „in my opinion“, „I might be wrong“ etc. just add copy/paste all these softeners from this signature to make reading more comfortable for you. Otherwise I’m a fine person which respects you and everyone and wants to be respected.
Staff Callum Posted June 1, 2023 Staff Posted June 1, 2023 Hi NotMyFault, I have logged this with our developers to be investigated further I'll update this thread once I have more info. Thanks C NotMyFault 1 Quote Please tag me using @ in your reply so I can be sure to respond ASAP.
NotMyFault Posted June 1, 2023 Author Posted June 1, 2023 I repeated the test, using a PT filter to create a linear gradient, and rectangle to polar filter. The only difference to a regular fill ist that no forced dithering gets applied. Using that layer no black dots occur. So the issue is created by forced dithering applied even to alpha channel when using gradients. Can be closed, i will bump the feature requests to get rid of forced dithering. Quote Mac mini M1 A2348 | Windows 10 - AMD Ryzen 9 5900x - 32 GB RAM - Nvidia GTX 1080 LG34WK950U-W, calibrated to DCI-P3 with LG Calibration Studio / Spider 5 iPad Air Gen 5 (2022) A2589 Special interest into procedural texture filter, edit alpha channel, RGB/16 and RGB/32 color formats, stacking, finding root causes for misbehaving files, finding creative solutions for unsolvable tasks, finding bugs in Apps. My posts focus on technical aspects and leave out most of social grease like „maybe“, „in my opinion“, „I might be wrong“ etc. just add copy/paste all these softeners from this signature to make reading more comfortable for you. Otherwise I’m a fine person which respects you and everyone and wants to be respected.
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