Dear all
I plan to do experiment that subjects look at some colors in display. At the beginning, I want to do gamma correction for display. I want to know gamma table or how to do gamma correction for display, especially RGB. My operating system is windows7.
Regards
Hi,
maybe this could help you: http://www.normankoren.com/makingfineprints1A.html#Gammabox
and
http://quickgamma.de/indexen.html
Best!
If you are using MatLab for image processing, have a look at this:
http://www.mathworks.com/matlabcentral/fileexchange/26523-the-inface-toolbox-v2-0-for-illumination-invariant-face-recognition/content/INface_tool/auxilary/gamma_correction.m
Gamma encoding is used to increase the quality of shadow values when an image is stored as integer intensity values, so to do gamma encoding you use the formula:
encoded = ((original / 255) ^ (1 / gamma)) * 255
Gamma decoding is used to restore the original values, so the formula for that is:
original = ((encoded / 255) ^ gamma) * 255
If the monitor does the gamma decoding, you would want to use the first formula to encode the image data.
Hi, the process may be a bit more complicated if you want to build your own gamma curves based on measurements, but in this case you need a spectrophotometer and an algorithmic solution to find the unknown parameters of the curves. Otherwise, the simple way is the classical power function with gamma values 1.0/2.2 because you want to render the image on the display.
I'd agree with Alessandro that displays and display drivers don't always apply their gamma the way the sRGB specs suggest, but will often shift the curves based on the preferences the user has set. The best option is to follow his suggestion and measure the value->luminance curves for each color channel and find the correspondences. "Visual Psychophysics" (MIT Press) discusses more detail of how to do this, and details on how a display converts image values into the displayed brightness. If you have a spectrophotometer, it'll work, but you'll need to convert the spectral measurements into luminance. If you have a luminance meter or a chroma meter available, those will integrate the measurement directly.
If you need more precision or need to be rigorous, use the sRGB specs (see the wikipedia link for equations). The oft-quoted gamma of 2.2 gets you close -- but it's actually a gamma of 2.4 with an offset.
https://mitpress.mit.edu/books/visual-psychophysics
https://en.wikipedia.org/wiki/SRGB
Hi everybody
The attached file is an implementation of gamma correction using
1- visual basic 0.6
2- Matlab
3- C#
4-Visual C++
Thanks
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