rgb2lab is returning unexpected results?

1 次查看（过去 30 天）
Roger Breton
Roger Breton 2021-12-16
评论： Image Analyst 2021-12-16
This is the code I'm running, nothing fancy :
>> rgb2lab([0 1 0],'ColorSpace','sRGB')
ans =
87.7347 -86.1827 83.1793
There must be an argument I'm missing, somewhere (?), because the result does not match all that well what other ICC-aware applications are leading me to believe about the "color appearance" of sRGB Green (RGB = 0 255 0) or [0 1 0], which is CIE Lab 88 -79 81.
87.7341 is perfect but -86.1827 and 83.1793 are not right.
I tried to use arguments like "Adapted White Point" but those are not defined in the function parameters, as far as I can humbly tell.
I tried with cform and applycform but the result is not directly interpretable in CIE Lab, so I can't tell for sure.
(I'll have to figure this one out one of these days, for my own curiosity: I guess the L is expressed on an 8bit 0-255 scale, so that's not the end of the world but the a* and b*? Hmmm. Something about subtracting or adding 128... But that's as far as I'm willing to go... for now)
  2 个评论
Image Analyst
Image Analyst 2021-12-16
What white points are you using? I've let the developers know and they might answer. In the meantime you can
>> edit rgb2lab.m
and see what you can learn though most of the computations are done outside that in a DLL.
Roger Breton
Roger Breton 2021-12-16
That's the "key"!!!!!
To match Photoshop and all other "ICC-based" applications, the white point has to be D50.
Silly me :-)
Now the result is perfect :
>> rgb2lab([0 1 0],'WhitePoint','d50')
ans =
87.8184 -79.2871 80.9893
Thank YOU SO VERY MUCH!!!!!!

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Image Analyst
Image Analyst 2021-12-16
Set the white point to be D50.
  2 个评论
Roger Breton
Roger Breton 2021-12-16
Never thought of chromatic adaptation... Egg on my face...
Image Analyst
Image Analyst 2021-12-16
Hey, don't feel bad. Everyone makes mistakes. And I've talked to the worlds leading experts in person and even they'll admit they don't know everything. This stuff is confusing even for them - that's why research keeps going on. We don't know everything yet. Because we have physics and optics intertwined with physiology and psychology and anatomical/biological differences, color science is one of the most bewildering fields of science. I'm sure you know lots of things that I don't.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Behavior and Psychophysics 的更多信息

标签

产品


版本

R2021b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by