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  1. Qt
  2. QTBUG-141255

Wrong conversion from ARGB with premultiplied alfa to FP16

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    • Icon: Bug Bug
    • Resolution: Fixed
    • Icon: P2: Important P2: Important
    • 6.8.6, 6.10.1, 6.11.0 Beta3
    • 6.9.3, 6.10.0
    • GUI: Painting
    • None
    • Intel X86_64 platform.
    • Windows
    • de1aff1b8 (dev), b37d0a67b (6.10), 4347c2fbb (tqtc/lts-6.8)

      In our writing tests with KImageFormat's EXR plugin, we noticed a significant conversion difference
      between ARM64 and AMD64. From our tests it appears that the problem occurs on Intel x86_64 (verified on Linux and Windows).

      The following QImage formats were incorrectly converted to Format_RGBA16FPx4:

      • Format_ARGB32_Premultiplied
      • Format_ARGB6666_Premultiplied
      • Format_ARGB8555_Premultiplied
      • Format_ARGB8565_Premultiplied
      • Format_RGBA8888_Premultiplied

      I've attached the source image used, an example of an FP16 image with the problem, and an FP32 image for comparison (unaffected).

      I've also included a small program to facilitate verification.

        1. fp16conv.zip
          11 kB
        2. rgba32premult_2_fp16.tif
          73 kB
        3. rgba32premult_2_fp32.tif
          145 kB
        4. source_rgba16.png
          source_rgba16.png
          8 kB
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            allan.jensen Allan Sandfeld Jensen
            mircomir Mirco Miranda
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              Created:
              Updated:
              Resolved:

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