Issue 620 in pdfium: wrong colors and render artifacts when rendering white image from pdf

[lic… via monorail]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 620 by lic...@gmail.com: wrong colors and render artifacts when rendering white image from pdf
https://bugs.chromium.org/p/pdfium/issues/detail?id=620

What steps will reproduce the problem?

1. render the attached pdf file with pdfium_test --png at different scales,
for example scale 1.0 to 1.6

What is the expected output? What do you see instead?

Expected output:

A white image where all pixels are rgb (255, 255, 255)

Observed output:

Depending on the render scale:

Scale 1.0: A white image where all pixels are rgb (253, 253, 253)
Scale 1.1 to 1.4: A White image composed of a grid-like pattern of lines in rgb (254, 254, 254) and rgb (255, 255, 255)
Scale 1.5: correct color, no artifacts
Scale 1.6: grid-like pattern again

The actual distribution and amount of render artifacts (grid pattern) depends on the scaling factor used.

What version of the product are you using? On what operating system?

current pdfium branch on Arch Linux (chromium/2886), also tested with chromium embedded viewer

Please provide any additional information below.

Since the render artifacts only differ by 1-2 pixels by color value from the expected output these are very hard to spot. You either need a sharp eye and a good monitor or you need to rely on image analysis tools.

Attachments:
blank_page.pdf 2.7 KB

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[thes… via monorail]

Comment #1 on issue 620 by the...@chromium.org: wrong colors and render artifacts when rendering white image from pdf
https://bugs.chromium.org/p/pdfium/issues/detail?id=620#c1

I'm curious how you spotted this. I certainly cannot with just my eyes. I ended up converting the PNG to PPM and looked at the values that way.

[thes… via monorail]

Updates:
Cc: cary...@google.com

Comment #2 on issue 620 by the...@chromium.org: wrong colors and render artifacts when rendering white image from pdf
https://bugs.chromium.org/p/pdfium/issues/detail?id=620#c2

I think this will get fixed once we switch rendering from AGG to Skia.

[lic… via monorail]

Comment #3 on issue 620 by lic...@gmail.com: wrong colors and render artifacts when rendering white image from pdf
https://bugs.chromium.org/p/pdfium/issues/detail?id=620#c3

Yeah, it's pretty elusive. I spotted it when looking at my laptops lcd screen from a bad angle. The pattern is kind of similiar to lines on images that have been scanned with a dusty scanner so it triggered my attention.

Would it help you if I'd retest this against a Skia-enabled build of pdfium?