[Arm-netbook] Alt Webpage & Logo Combo

[rhkramer at gmail.com]

On Saturday, February 03, 2018 09:02:10 AM rhkramer at gmail.com wrote:
> I did find a bug report not too long ago for some application which
> actually confirmed the bias I described, and described how that worked (in
> general terms)--I'll make a cursory search or try to remember where I
> found that, and, if I do, I'll post it here.

Ahh, that was easier than I expected--here are my notes after reading that bug 
report (some time ago)--I did not re-read it today to see if anything has 
changed.  The comments immediately after the [[<URL>][<Page Title>]] are my 
own, the things after the ` are quotations from the bug report.

   * [[https://bugs.freedesktop.org/show_bug.cgi?id=13431][Bug 13431: Summary: 
Gamma not taken into account, white on black hard to read]]--this confirms my 
observation of the problem, but my explanation (iirc) predates gamma 
correction (iir/uc)--my theory of the cause of the problem is that anti-
aliasing sort of "assumed" that the normal view would be black on white, when 
it was applied to white on black, it should have somehow considered the other 
"color" (black or white) to be the basis--because it didn't, fewer pixels are 
colored white when viewing white on black as opposed to the number of pixels 
colored black when viewing black on white.  I don't know if the problem still 
exists--it probably does in at least some places, and, I still have more 
difficulty reading white (or a light color) on a black (or dark background).
`
When doing antialiasing, fontconfig-based renderers do not take gamma into 
account and assume a linear color space. This make black on white text difficult 
to read at small font sizez.

...

The reason is that the stems of the glyphs are thinner than a whole pixel. 
Therefore, they get a fractionnal value. For example, the pixels on the lower 
part of the stem of the 'f' get the pixel value 151/255 in black on white, and 
104/255 in white on black (and 104+151=255). With the usual 2.2 gamma, this 
makes respectively 32% and 14%, which gives a contrast of 68% for black on 
white, and 14% for white on black.
'