Re:Image Dithering: Eleven Algorithms and Source Code
by leni536 on Tuesday October 10, 2017 @05:59AM
(#15440605)
> I was surprised that the prints were better without adjusting for gamma.
Ha, it was the same for me. I used imageworsener where I had to explicitly specify -nogamma for this effect.
An other place where wrong gamma handling accidentally works is text anti-aliasing. It turns out that for small font size the wrong handling of colorspace results in more readable text than the gamma-correct method only for dark text on light background [1]. No wonder people don't like to use light fonts on dark background (like terminals).
[1] https://www.freetype.org/freetype2/docs/text-rendering-gener...
Specifically, I used the ImageMagick operations "-dither FloydSteinberg -monochrome" for more contrast or "-dither FloydSteinberg -remap pattern:gray50" for more fidelity to the original image.
I was surprised that the prints were better without adjusting for gamma. If I converted the image to a linear color space before the dither operation, the print came out too dark. I'm guessing that the gamma in the non-linear color space compensated for the dot gain on the printer to cancel out the effect.