MATLAB: How many matrix need to change to make a mean&median filter

mean filter

if i want to make a mean&median filter,thats mean i must change the red,green and blue matrix in the pixel image,is that right? lets say if the image size is 200×200,that's mean i must change every pixel in the image and the computer will take a very long process?

sorry for my bad english

Best Answer

You don't need to change them. You can have a separate output image and leave your input image unchanged. It will create an output image, and for a small image like 200x200 it will be very fast. It took 0.008 seconds for all three color channels on my computer. Seems very fast to me - how fast do you need?

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MATLAB: Change color in image

Why don't you have access to the original image? If you don't, for some strange reason, then you can find the pixels by first extracting the individual color planes, then median filtering them and replacing the colored pixels with the median filtered pixels. It will work a lot better if you have the original uncompressed image, rather than the blurry one you uploaded, which does not have sharp graphics.

rgbImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 3.
[rows columns numberOfColorBands] = size(rgbImage);
% Display the original color image.
subplot(2, 2, 1);
imshow(rgbImage);
axis on;
title('Original Color Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% Then do a median filter on each one.  
medianRed = medfilt2(redChannel, [7 7]);
medianGreen = medfilt2(greenChannel, [7 7]);
medianBlue = medfilt2(blueChannel, [7 7]);
% Display the image.


subplot(2, 2, 2);
imshow(medianRed);
title('Red Median Image', 'FontSize', fontSize);
% Then find the pure color pixels.
thresholdValue = 40;
pureRed = redChannel >= thresholdValue & greenChannel < thresholdValue & blueChannel < thresholdValue;
pureGreen = redChannel < thresholdValue & greenChannel >= thresholdValue & blueChannel < thresholdValue;
pureBlue = redChannel < thresholdValue & greenChannel < thresholdValue & blueChannel >= thresholdValue;
% Display the image.
subplot(2, 2, 3);
imshow(pureRed);
title('Red Mask Image', 'FontSize', fontSize);
% Then replace each pure color with the median from that channel.
redChannel(pureRed) = medianRed(pureRed);
greenChannel(pureGreen ) = medianGreen(pureGreen );
blueChannel (pureBlue ) = medianBlue(pureBlue );
% Construct the new color image
rgbImageFixed = cat(3, redChannel, greenChannel, blueChannel);
% Display the image.
subplot(2, 2, 4);
imshow(rgbImageFixed);
title('Fixed RGB Image', 'FontSize', fontSize);

MATLAB: Calculate patch of rgb image

What are you averaging? The whole 4x4x4 cube? Or just a 2D 4x4 square on a color channel by color channel basis? And more importantly, why?

You can extract the color channels and get the average like this:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
kernel = ones(4)/16;
blurredRed = conv2(double(redChannel), kernel, 'same');
blurredGreen = conv2(double(greenChannel), kernel, 'same');
blurredGreen = conv2(double(blueChannel), kernel, 'same');
blurredRGB = cat(3, blurredRed, blurredGreen, blurredBlue);

Or you can blur the colors while mixing colors by using convn

blurredRGB = convn(double(rgbImage), ones(4,4,4)/64, 'same');

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MATLAB: Change color in image

MATLAB: Calculate patch of rgb image

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