How can I correction hue values of image

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How can I correction hue values of image
Fu-An Nung
Fu-An Nung on 17 Oct 2016
I have a wrong tonal image.I want to make it have correct tonal.

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Accepted Answer

Image Analyst
Image Analyst on 17 Oct 2016
You need to snap an image of a color standard with known color values. The usual standard is the x-rite Color Checker Chart. Then you have known XYZ values. You can use least squares to derive a transform to convert your RGB values, of the color chips on a picture of that chart that you have taken, into XYZ values. Then you can use analytical formulas to convert XYZ into LAB or other calibrated color spaces.
Image Analyst
Image Analyst on 17 Oct 2016
Try this:
close all;
fontSize = 15;
format compact
format short g;
rgbImage = imread('peppers.png');
subplot(2, 4, 1);
axis on;
title('Original Image', 'FontSize', fontSize);
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
hsvImage = rgb2hsv(rgbImage);
hImage = hsvImage(:, :, 1);
sImage = hsvImage(:, :, 2);
vImage = hsvImage(:, :, 3);
subplot(2, 4, 2);
imshow(hImage, [0, 1]);
title('Hue Image', 'FontSize', fontSize);
subplot(2, 4, 3);
imshow(sImage, []);
title('Saturation Image', 'FontSize', fontSize);
subplot(2, 4, 4);
imshow(vImage, []);
title('Value Image', 'FontSize', fontSize);
someFactor = 1.6; % or whatever.
% Use mod to "wrap around" values more than 1.
hImageNew = mod(hImage * someFactor, 1);
subplot(2, 4, 6);
imshow(hImageNew, [0, 1]);
title('New Hue Image', 'FontSize', fontSize);
% Create new image
hsvImage = cat(3, hImageNew, sImage, vImage);
% Convert back to RGB color space.
rgbImageNew = hsv2rgb(hsvImage); % It's double in the range of 0-1 here.
% Convert to uint8 in the range 0-255
rgbImageNew = uint8(255 * mat2gray(rgbImageNew));
subplot(2, 4, 5);
title('Changed Image', 'FontSize', fontSize);

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