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IDProjectCategoryView StatusDate SubmittedLast Update
0002153NoesisGUIC# SDKpublic2021-10-20 02:202021-10-20 13:01
ReporterDavidYawCSpeed Assigned Tosfernandez  
PrioritynormalSeverityminor 
Status resolvedResolutionfixed 
Product Version3.1.1 
Target Version3.1.2Fixed in Version3.1.2 
Summary0002153: PNG Alpha Transparency not applied properly depending on PNG format
Description

We've got a PNG image which is not 32-bit RGBA. When displayed in some contexts, the alpha is not blended with the background properly.

I have seen this issue on both Windows x64 and Linux ARM64.

Workaround: Convert the image to full RGBA.

Attached:

  • Both the PNG that causes the issue, and the result of converting it to RGBA, which fixes the issue.
  • Screenshot of the issue occurring on Windows x64. It ends up drawing black.
  • Picture of the issue occurring on Linux ARM64, on our real device. It ends up drawing transparent, so the video overlay shows through.
Steps To Reproduce

I can reproduce the issue very reliably in our real application, but in the real application, the Image object is 20 levels deep in the Visual Tree. But in a standalone application, with just the Image over top of a colored background, it works fine. Unfortunately, I'm not sure exactly what UI Controls need to be set up in order to trigger this bad alpha blending.

However, I do know what is needed in a PNG image.

Examining the images under Linux:



$ file *.png

icon_batt_plug_in_broken.png: PNG image data, 128 x 128, 8-bit gray+alpha, non-interlaced

icon_batt_plug_in_works.png:  PNG image data, 128 x 128, 8-bit/color RGBA, non-interlaced

Using https://www.nayuki.io/page/png-file-chunk-inspector:

  • Broken
    • Bit depth: 8 bits per channel
    • Color type: Grayscale+Alpha (4)
  • Works
    • Bit depth: 8 bits per channel
    • Color type: RGBA (6)
Attached Files
icon_batt_plug_in_broken.png (1,459 bytes)   
icon_batt_plug_in_broken.png (1,459 bytes)   
icon_batt_plug_in_works.png (8,989 bytes)   
icon_batt_plug_in_works.png (8,989 bytes)   
Windows-ScreenshotTestApp.png (4,503 bytes)   
Windows-ScreenshotTestApp.png (4,503 bytes)   
Linux-PictureOfRealApp.jpg (37,030 bytes)   
Linux-PictureOfRealApp.jpg (37,030 bytes)   
PlatformAny

Activities

Issue History

Date Modified Username Field Change
2021-10-20 02:20 DavidYawCSpeed New Issue
2021-10-20 02:20 DavidYawCSpeed File Added: icon_batt_plug_in_broken.png
2021-10-20 02:20 DavidYawCSpeed File Added: icon_batt_plug_in_works.png
2021-10-20 02:20 DavidYawCSpeed File Added: Windows-ScreenshotTestApp.png
2021-10-20 02:20 DavidYawCSpeed File Added: Linux-PictureOfRealApp.jpg
2021-10-20 02:25 DavidYawCSpeed Description Updated
2021-10-20 02:41 DavidYawCSpeed Steps to Reproduce Updated
2021-10-20 10:28 sfernandez Assigned To => sfernandez
2021-10-20 10:28 sfernandez Status new => assigned
2021-10-20 10:28 sfernandez Target Version => 3.1.2
2021-10-20 13:01 sfernandez Status assigned => resolved
2021-10-20 13:01 sfernandez Resolution open => fixed
2021-10-20 13:01 sfernandez Fixed in Version => 3.1.2