demo
====
prime.offload:
iGPU: 220FPS
dGPU: starts above 200FPS but slows down to 77FPS
prime.sync:
dGPU: starts at 140FPS and slows down to 113FPS
or
dGPU: starts at ~300FPS and slows down to 188FPS
slowdown seems to be related to GPU thermal throttling reacting to increased CPU
temperatures
color
=====
we are trying to figure out how the luminance % is derived on:
<http://www.workwithcolor.com/hsl-color-picker-01.htm>
additional information here shows the same 44% luminance assigned to blue but doesn't
describe the forumula:
<http://www.workwithcolor.com/color-luminance-2233.htm>
this assigns the following 44% "equal luminance" values of the 3 color primaries:
0x0000FF (0, 0, 255) [1.0]
0x009000 (0, 144, 0) [0.5647]
0xD20000 (210, 0, 0) [0.8235]
although when converted to grayscale these colors are "less equal", they *seem* more
equivalent to the eye when fully saturated.
these are the following colors of equal luminance as predicted by Oklab:
0x0000FF (0, 0, 255) [1.0]
0x006B00 (0, 107, 0) [0.4196]
0xAB0000 (171, 0, 0) [0.6705]
these are the following colors of equal luminance as predicted by the ITU-R BT.601
formula $Y' = R' * 0.299 + G' * 0.587 + B' * 0.114$ where blue has $Y' = 0.114$; note
R', G', and B' are gamma-corrected sRGB values:
0x0000FF (0, 0, 255) [1.0]
0x007A00 (0, 122, 0) [0.4780]
0xA60000 (166, 0, 0) [0.6509]
we also have the ITU-R BT.709 formula
$E'_Y = E'_R * 0.2126 + E'_G * 0.7152 + E'_B * 0.0722$
0x0000FF (0, 0, 255) [1.0]
0x005900 (0, 89, 0) [0.3490]
0x9D0000 (158, 0, 0) [0.6177]
there is also the "HSP" formula, based on the BT.601 formula for "perceived brightness",
$P = sqrt (0.299 * R^2 + 0.587 * G^2 + 0.114 * B^2)$; this gives $P = 0.3376$ for blue,
but for pure spectral colors it seems to give the same results as BT.601:
0x0000FF (0, 0, 255) [1.0]
0x007A00 (0, 122, 0) [0.4780]
0xA60000 (166, 0, 0) [0.6509]
