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tom · Guest

I would like to extract the brightness from a picture using ntsc or
photoshop or linear color weights (this is quite easy and done) but how
could you go about using this gray scale pic to change the brightness of
the original picture,just to compare which weighted numbers are the best. I
have HSV working well for a lot of things but it takes the the highest
number from the three colors not weighted number. Does any color space use
weighted numbers?

thanks
Tom

northern_RATT · Guest

[snip]

tom · Guest

thanks but NTSC is more like (0.299f * red) + ( 0.587f * green) + (
0.114f * blue)
Photoshop (according to the 'NET' )is (0.2126f * red) + ( 0.7152f *
green) + ( 0.0724f * blue)
I already use these to extract the gray value but I would like to compose a
new image with these values and color information to compare with the
original to see how accurate these values are. e.g.. why did adobe use these
numbers. the problem is if you use the same system for composing a image as
you used for extracting they should be identical, not giving any pertinent
information.
I do know about Yuv and Yiq but you have to use the same weighted numbers.

thanks again
Tom

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