how to know if the image is homogeneous

i have a set of images and i'd like to extract from them the homogeneous images, like this following one (what i mean of homogeneity means have same degree of color):

Answer 1

[Image Analyst]

Extract the separate color channels:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);

then call unique() and if the length is 1, it's homogenous in that color channel

if length(unique(redChannel)) == 1
  % Only one color so it's homogenous
end

Or you could check the variance

if var(redChannel(:)) == 0

Or you could call std() or imhist(). There are a multitude of ways.