Match image color based on a reference, and save the transformation for more images.

image_match.m

color_mode = 'ycbcr'; %rgb, ycbcr, hsv

work_patch = 'E:\!Scan\image match\';

ref = imread([work_patch,'ref.bmp']); % Your reference image
A = imread([work_patch,'img.bmp']); % Your scan that needs to be calibrated

numColorChan = size(ref,3);
isColor = numColorChan > 1;

if isColor
    switch color_mode
        case 'ycbcr'
            ref=rgb2ycbcr(ref);
            A=rgb2ycbcr(A);
        case 'hsv'
            ref=im2double(ref);
            ref=rgb2hsv(ref);
            A=im2double(A);
            A=rgb2hsv(A);
    end
end

% Anything beyond 256 will essentially give the same result. If you want
% the color to be closer to your ref, you can choose lower value but
% obviously that will result in banding (because it also decides how many
% discrete colors your result will have.
N = 1000;

% Compute histogram of the reference image
hgram = zeros(numColorChan,N);
for i = 1:numColorChan
    hgram(i,:) = imhist(ref(:,:,i),N);
end

% Adjust A using reference histogram
hgramToUse = 1;
for k = 1:size(A,3) % Process one color channel at a time
    if isColor
        hgramToUse = k; % Use the k-th color channel's histogram
    end
    for p = 1:size(A,4)
        % Use A to store output, to save memory; T is the transformation
        % matrix
        [A(:,:,k,p), T(k,:)] = histeq(A(:,:,k,p), hgram(hgramToUse,:));
    end
end

%%
% This is your image after matching.
if isColor
    switch color_mode
        case 'ycbcr'
            A=ycbcr2rgb(A);
            imwrite(A,'match_ycbcr.bmp');
        case 'hsv'
            A=hsv2rgb(A);
            imwrite(A,'match_hsv.bmp');
        otherwise
            imwrite(A,'match_rgb.bmp')
    end
else
    imwrite(A,'match_grey.bmp');
end

%% Batch process other images

%myfolder='E:\!Scan\_temp\backup'; % load other images E:\!Scan\_temp\done
myfolder=[work_patch,'todo'];

newfolder =[myfolder,'_changedcolor']; % result folder
mkdir(newfolder);

files = [dir(fullfile(myfolder,'*.jpg')); dir(fullfile(myfolder,'*.bmp')); dir(fullfile(myfolder,'*.png'))];

for file = files'
    fullfilename = fullfile(file.folder, file.name);
    new=imread(fullfilename); % Now load another image.
    
    switch color_mode
        case 'ycbcr'
            new=rgb2ycbcr(new);
        case 'hsv'
            new=im2double(new);
            new=rgb2hsv(new);
    end
    
    for k = 1:size(A,3)
        % Use the same transformation. make sure you have
        % grayxformmex.mexw64 in your working path.
        new(:,:,k)=grayxformmex(new(:,:,k),T(k,:));
    end
    switch color_mode
        case 'ycbcr'
            new=ycbcr2rgb(new);
        case 'hsv'
            new=hsv2rgb(new);
    end
    
    imwrite(new,fullfile(newfolder,[file.name,'.bmp']));
end