Color issue: RGB 217 becomes 224.

[cheonman]

SumatraPDF version

• Version 3.5.2 x64 and pre-release (3.6.16354 x64)

Describe the bug
PDF with A) included image and B) colored shape, where A) and B) should have the same background color of RGB (217,217,217), shows RGB (217,217,217) for the image and RGB (224,224,224) for the shape.

To Reproduce
Steps to reproduce the behavior:

1. Open test.pdf in SumatraPDF.
2. The QR-Code shows a different background color (gray) than the surrounding shape.
3. Compare this with Acrobat Reader, Firefox, Google Chrome, Foxit Reader, PDFgear, Inkscape. They all show no difference in the background color.

Expected behavior
The identical color should be displayed, i.e., RGB (217,217,217).

File that reproduces the problem
test.pdf

Screenshots
SumatraPDF:
Acrobat Reader:

Additional context
The PDF was exported from PowerPoint.

[GitHubRulesOK]

suspect its the long term MuPDF issue was only "partially fixed" last time reported, so at least 2 similar open issues.
image vectors are primarily (fuzzy) ��� (NULLs) on a (predominantly ) RGB field of ÙÙÙ (D9's=217s) page grey slab is .851 g of 1 (217.005) as image background also included is the image boundary as .608 .0392 .49 rg [155 10 125] so a lot of colour transforms in the mix to interfere.

However agreed that without any colour profile then [127 127 127] overlaid on 127 box the expectation is 0,0,0 differential.

MuPDF seems to have a 7 bit shift so is that a significant miscalculation or an unwanted deliberate device colour correction ? previous open issue where colour was improved but greys were not #394 Also related to grey transparency #1103

[kjk]

I've opened https://bugs.ghostscript.com/show_bug.cgi?id=707847