[cairo] Linear colorspace not a good idea

[Owen Taylor]

On Mon, 2006-03-13 at 14:13 -0800, Bill Spitzak wrote:

> Another serious problem is that sometimes people want the perceptual 
> result of the composite rather than the true result. The most obvious 
> example is text and thin lines, drawn in different colors on different 
> backgrounds. People expect the same image drawn in different colors 
> (such as white on black verses the inverse) will look the same thickness 
> and weight. Unfortunately this is not true at all in linear space: the 
> black lines look much thinner than white lines. But in sRGB it does 
> appear to work, because it is much closer to perceptually linear. Every 
> line graphics and work processor program in the world relies on this.

This is not true in my experience. White-on-black and black-on-white
text look more balanced in weight with compositing done in linear
color space.

 http://people.redhat.com/otaylor/fonts/gamma-screenshots/

Has some images, though they aren't really set up for side-by-side
comparison. They aren't perfectly balanced with linear compositing
either, which may indicate that there is a perceptual effect, but 
it is weaker than the effect you get from compositing in sRGB space.

						Owen