MATLAB: How to extract colour descriptor (set of features) from the image

color spacegamuthistogramimage processingImage Processing Toolbox

Hello, I have the following task. I want to compute the color histogram of an Image in HSV color space. For that I want to uniformly quantize the HSV color space into 240 cubes in which the quantization of each channel is 15 hues (H), 4 saturations (S) and 4 intensities (V ) respectively. And after making this color histogram the values of each bin is my 240 dim vector of color features which I want to get finally. Could someone please help me with the m-code for this task or with the high level plan how to create it? I will really appreciate it. Thank you.

Best Answer

Loop over every pixel in the image and determine the bin, then increment the count. Here's a start

[rows, columns, numberOfColorChannels] = size(rgbImage);
hsvImage = rgb2hsv(rgbImage); % Ranges from 0 to 1.
hsvHist = zeros(15,4,4);
for col = 1 : columns
    for row = 1 : rows
        hBin = floor(hsvImage(row, column, 1) * 15);
        sBin = floor(hsvImage(row, column, 2) * 4);
        vBin = floor(hsvImage(row, column, 3) * 4);
        hsvHist(hBin, sBin, vBin) = hsvHist(hBin, sBin, vBin) + 1;
    end
end

Related Solutions

MATLAB: How to display the intensity of 2D image as a colormap

You need to pass in a colormap, N-by-3 array with values between 0 and 1, to to the colormap() function, NOT an image. And you should probably also pass in a handles to the axes you want to apply it to, otherwise it will apply that colormap to every axes in the figure window, which is probably not what you want. So in short, you want:

myColorMap = hsv(256);      % Create a colormap.


colormap(gca, myColorMap);  % Now apply the colormap.

You can also pass the colormap directly into imshow() and skip calling the colormap() function if you want.

See this full demo and study it:

grayImage = imread('cameraman.tif');
subplot(3, 1, 1);
imshow(grayImage);
axis('on', 'image');
title('Original Image');
subplot(3, 1, 2);
% Create a colormap.
myColorMap = hsv(256);
% Display image with that colormap.
imshow(grayImage, 'Colormap', myColorMap);
colorbar;
axis('on', 'image');
title('Overlay Image');
% Or equivalently, using the colormap() function:
subplot(3, 1, 3);
% Display image with no colormap.
imshow(grayImage);
% Create a colormap.
myColorMap = hsv(256);
% Now apply the colormap.  Pass in the axes or else it will apply the colormap
% to ALL images on the figure, which is probably not what you want.
colormap(gca, myColorMap);
colorbar;
axis('on', 'image');
title('Overlay Image');

Now, if you already have a colormap, and you want to produce an RGB image, like to write to a file on disk rather than just pseudocoloring a displayed image, you want to call ind2rgb()

rgbImage = ind2rgb(grayImage, myColorMap);

MATLAB: Generating a HSV Histogram without For-loops

No loop needed.

h = hsvVid(:,:,1,frame);
idxH = max(1, ceil(h*12));
H = histc(idxH(:), 1:12);

Best Answer

Related Solutions

MATLAB: How to display the intensity of 2D image as a colormap

MATLAB: Generating a HSV Histogram without For-loops

Related Question