MATLAB: Is there a way to compute the percentage of pixels in this image of a certain colour, whilst ignoring the (dark blue) background in the calculation

digital image processingimage analysisimage processingimage segmentationMATLAB

Hi,

I'm trying to get the percentages of different coloured pixels in this image, but haven't found a way to either ignore the background or to ignore it in the percentage calculations. Any help would be appreciated!

Best Answer

If I is your image.....And your pixel value is n. Use:

idx = I==n ;

YOur idx will be a matrix with 1's and 0's...

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MATLAB: How to detect colors in images

There are many cool demos in my File Exchange: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862. Start there, then come back with any questions specific to your images and attach your code and image(s) if you want help.

MATLAB: Adjust percentage of red green blue in RGB

If you just want to amplify the red values by a factor of 1.5678 then:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% Multiply red by some factor:
amplitudeFactor = 1.5678; % Whatever you want.
redChannel  = uint8(double(redChannel) * amplitudeFactor);
% Recombine separate color channels into a single, true color RGB image.
rgbImage = cat(3, redChannel, greenChannel, blueChannel);
imshow(rgbImage);

In your code, there is no reason to ask for the image file format and pass it in to imread unless the image does not have a file extension or the file extension is incorrect. If that's the case it would be better to correct that rather than to ask for format and pass it in. imread() will figure out the format from the filename extension.

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MATLAB: Adjust percentage of red green blue in RGB

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