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TrueColor / sRGB image saved as 8-bit Indexed

See original GitHub issue

Prerequisites

I have written a descriptive issue title
[x ] I have verified that I am using the latest version of Magick.NET

System Configuration

Magick.NET version: Magick.NET-Q16-HDRI-x64-OpenMP
Environment (Operating system, version and so on): Windows 10

Question

I have an image created using Clut(). The source colors are very few. Now when I save as a PNG with ColorSpace set to sRGB and ColorType set to TrueColor, the image is still saved as an indexed 8-bit image. AFAIK, this only happens when the color range in the image is small. Am I doing something wrong?

Issue Analytics

State:
Created 5 years ago
Comments:12 (1 by maintainers)

Top GitHub Comments

2reactions

t246246commented, Mar 7, 2020

I’m loading a RGB 8 bit gray image, the ColorType is set to TrueColor. When I write out the image as a tif I get a grayscale (single channel) image, and the ColorType has changed to Grayscale.

You’ll need -define colorspace:auto-grayscale=off. In Magick.NET use SetAttribute("colorspace:auto-grayscale", "false");

2reactions

FrogsInSpacecommented, May 28, 2019

Just stumbled over the same issue: images containing only few colors were saved to Png8, despite ColortType.TrueColor etc… in the original image. But i found that there is s specific MagickFormat.Png00 type which saves the png using the same bitdepth / colortype as the original. I would have assumed that the naming would be the other way arround: MagickFormat.Png doing no optimization/conversion at all , and a specific name doing them … Nevertheless , my issue was solved by using MagickFormat.Png00