Hi, Nicolas George wrote: > > - Our brain lies to us about colors all the time.
This begins already with the combination of light receptors and the first nerve cells in the chain which creates the color evaluations. As mammals we should normally be blind against red-yellow-green contrasts. Dogs and cats perceive colors only as contrast of blue and yellow. But as primates we benefit from a mutation which has split the yellow receptors into read and green ones and a copy of the blue-yellow contrast evaluator nerve cells. (This hacked us into the communication between plants and birds or insects). So our color perception is the combined evaluation of a blue-yellow contrast and a red-green contrast. The old yellow impression is now the impression of less blue than the average of red and green plus red and green being quite equally strong: xterm -bg '#FFFF80' & Brightness and color strength are not the same, because brightness is mainly perceived by the black-white receptors of which we have much more than color receptors. (Thus nightly black-and-white view.) On my screen i (individually) see pure green brighter than pure red which is brighter than pure blue: xterm -bg '#ff0000' & xterm -bg '#00ff00' & xterm -bg '#0000ff' & Nevertheless a slight overweight of blue can create a blue-ish impression: xterm -bg '#e0e0ff' & Note that the sum of red and green is 1.75 times brighter than blue. So the calibration of colors matches my individual eye color chemistry quite well, at the expense of a skew in brightness. In my youth i had discussions with anthroposophists who disputed the physical nature of light colors as spectrum of wavelengths. Their main argument for Goethe's color ideas was the fact that at the blue end of the spectrum they can see red comming back as violet. Thus the idea of a color circle. Actually this reddish impression comes from the fact that the red receptors are a bit more sensitive to blue than the green receptors. So the sensed color is much-more-blue-than-yellow + slightly-more-red-than-green = deep blueish violet. Emanuel Berg wrote: > what would you do to > write a function that will return a RRGGBB that is always blue > and as many blues as possible possible? I'd try to follow above principles and expect a certain grey zone where individual light sources and eyes deviate in display and perception from the numerical RGB values. I.e. every RGB vector where B is significantly larger than (R+G)/2 should appear as blueish, or else the RGB light source or the eyes can be considered non-mainstream. Have a nice day :) Thomas
