Using `-define tiff:alpha=associated` results in modified semi-transparent areas

ImageMagick version

7.1.0-60

Operating system

Windows

Operating system, version and so on

Windows 11

Description

There is already a longer discussion about it: https://github.com/ImageMagick/ImageMagick/discussions/2839

The short version:

• Not using -define tiff:alpha=associated results in the correct output, but unfortunately Adobe InDesign does not handle the background as transparent in that case (Photoshop and Gimp do)
• Using -define tiff:alpha=associated makes the background transparent, but modifies the semi-transparent areas of the image
• There is a flag in Gimp when exporting an image as a TIFF which seems to have the same function as the IM define and it gives the correct output without any modifications to semi-transparent pixels in both cases
  

Steps to Reproduce

• Run magick convert original.png -define tiff:alpha=associated associated.tiff
• Semi-transparent pixels are less white than in the original image

Images

Start by reproducing the issue with magick convert original.png -define tiff:alpha=associated associated.tiff and compare the semi-transparent pixels with the original. Read discussion #2839 for the existing context and use the GIMP behavior described there as the reference; done means associated alpha works for InDesign without modifying semi-transparent areas.