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1.9.8: A paletted 4-bit PNG image is displayed incorrectly when zoomed in

Posted: Mon Dec 15, 2025 4:29 pm
by Lord_D
XnView: MP 1.9.8 - 64 bit
OS: Windows 10 - 64bit

When a paletted 4-bit PNG is zoomed in, it turns into a series of stripes. Apparently, one column stretches across the entire width of the image.
gradient_dither.png
screenshot.png
ImageMagick command to create such images:

Code: Select all

magick.exe input.png -remap eink_cmap.gif output.png
Effect: A paletted 4-bit PNG display incorrectly when zoomed in.

To reproduce:
1. Open attached gradient_dither.png in XnView MP.
2. Zoom in more than 100%.
Actual behaviour (bug): The image turns into a series of stripes :bug:

Expected behaviour: The image is displayed correctly.

Re: 1.9.8: A paletted 4-bit PNG image is displayed incorrectly when zoomed in

Posted: Mon Dec 15, 2025 4:43 pm
by user0
I can reproduce, caused by antialiasing zoom-in filters (all except bilinear)
however, no issues with same filters during zoom-out