putPixels ignores transparency in Grayscale and Lab documents

Photoshop UXP Plugin API
1

@samgannaway In an RGB document, imaging.putPixels can write partly transparent pixels to a layer. In a Grayscale or Lab document, the same call makes every pixel fully opaque, and it doesn’t raise an error.

The docs list Grayscale-with-alpha and Lab-with-alpha as supported formats, so I expected them to work like RGB.

To reproduce:

  1. Load the attached plugin in the UXP Developer Tool and open its panel.
  2. Click Run all.
  3. It creates a small document per test and writes a fade from transparent to opaque. In the RGB documents you see the fade. In the Grayscale and Lab documents you see a solid block. The console shows a pass or fail for each test.

Tested in Photoshop 27.12.0 on macOS 14.4.1, in 8-bit and 16-bit documents.

2

@HeyEvgenii I never heard anything back about this, have you? I just created a plugin to demo the issue and also posted it to Photoshop Prerelease.

3

Hey, unfortunately not, but I have just highlighted this issue during Adobe Developers Live, hopefully it gets resolved

4

Awesome, I meant to check that out, but I didn’t. If you need any support on this issue just let me know!