Greyscale an image via replacing pixels

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Anna
Anna 2013-8-6
I have an image that I want to greyscale. It contains only blue and white pixels and I want to use a method whereby I identify the blue pixels and make them grey. How can I do that?
So far I have got:
fit = imread('RGB.jpg');
size(fit)
imshow(fit);
So I haven't got very far. I have created a function to test if a pixel is blue. Is there any way to use this? An example of using pixels to replace would be much appreciated.

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回答（1 个）

Ashish Uthama
Ashish Uthama 2013-8-6
% air code (untested)
red = fit(:,:,1);
green = fit(:,:,2);
blue = fit(:,:,3);
isblue = blue>250;
% Use logical indexing to set the red and green channels to be the same value as the blue channel. (When R==G==B, then the color is 'gray')
red(isblue) = blue(isblue);
green(isblue) = blue(isblue);
% reassemble
fitout = cat(3, red, green, blue)

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