Can we use standard deviation of color image as a contrast value?
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dila suay
am 18 Mär. 2023
Kommentiert: Walter Roberson
am 21 Mär. 2023
Hello,
Is it possible to compare the contrasts of 2 image by comparing std2(rgbimage) or is it necessary to convert to gray scale? Can you describe what is the difference between them?
Thank you
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Walter Roberson
am 19 Mär. 2023
That particular kind of contrast is called RMS contrast; there are other contrast measures as well.
YourImage = imread('flamingos.jpg');
c3 = std2(im2double(YourImage), [], [1 2]);
would give you the contrast of each color pane independently, giving you a 1 x 1 x 3 result.
But then what do you with the vector of 3 results? You could interpret them as an RGB color
image(c3)
but does it make sense for "contrast" to be interpreted as a color??
If you examine the other kinds of contrast measures, they mostly work with luminance -- requiring that you convert to grayscale or Lab or similiar first.
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Walter Roberson
am 21 Mär. 2023
Thought experiment:
Are the contrasts of all of these the same, or are some different?
[255, 0, 0, 0, 0]
[255, 0, 255, 0, 0]
[255, 255, 0, 0, 0]
[0, 255, 255, 0, 0]
[0, 0, 255, 0, 0]
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Sulaymon Eshkabilov
am 18 Mär. 2023
Numerically to find the differences of the two imaes (of the same size) and then compute the std of the computed differences are feasible, e.g.:
A = imread('A_RGB.png'); % Size is 1000-by-1200 RGB image
B = imread('B_RGB.png'); % Size is 1000-by-1200 RGB image
diff_AB = A-B;
std_diff=std2(diff_AB); % STD of the difference
3 Kommentare
Sulaymon Eshkabilov
am 18 Mär. 2023
if you're looking for an RMS contrast value, then you can easily implement the calculation equation given here into your code:
Which is applicable for RGB and grey images.
Simple calc of the grey image contrast value is:
IM = imread(GImage);
IM_contrast = max(IM(:))-min(IM(:));
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