Applies a GNU Octave/MATLAB equivalent colormap on a given image

dst = cv.applyColorMap(src, colormap)
dst = cv.applyColorMap(src, userColor)
dst = cv.applyColorMap(..., 'OptionName',optionValue, ...)

Input

• src The source image, grayscale or color of type uint8.
• colormap The colormap to apply. A string, one of:
  • Autumn Shades of red and yellow color map.
  • Bone Gray-scale with a tinge of blue color map.
  • Jet Variant of HSV.
  • Winter Shades of blue and green color map.
  • Rainbow Red-orange-yellow-green-blue-violet color map.
  • Ocean Black to white with shades of blue color map.
  • Summer Shades of green and yellow colormap.
  • Spring Shades of magenta and yellow color map.
  • Cool Shades of cyan and magenta color map.
  • HSV Hue-saturation-value color map.
  • Pink Pastel shades of pink color map.
  • Hot Black-red-yellow-white color map.
  • Parula Blue-green-orange-yellow color map.
• userColor The colormap to apply of type uint8 (1 or 3 channels) and length 256.

Output

• dst The result is the colormapped source image. Same row/column size and same type as src.

Options

• FlipChannels whether to flip the order of color channels in output dst, from OpenCV's BGR to between MATLAB's RGB. default true

The human perception isn't built for observing fine changes in grayscale images. Human eyes are more sensitive to observing changes between colors, so you often need to recolor your grayscale images to get a clue about them. OpenCV now comes with various colormaps to enhance the visualization in your computer vision application.

The second variant of the function applies a user-defined colormap on the given image.

Example

In OpenCV you only need cv.applyColorMap to apply a colormap on a given image. The following sample code takes an image and applies a Jet colormap on it and shows the result:

% We need an input image. (can be grayscale or color)
img_in = im2uint8(mat2gray(peaks(500)));

% Apply the colormap
%img_color2 = im2uint8(ind2rgb(img_in, jet(256)));
img_color = cv.applyColorMap(img_in, 'Jet');

% Show the result
imshow(img_color)

Example

cmaps = {'Autumn', 'Bone', 'Jet', 'Winter', 'Rainbow', 'Ocean', ...
    'Summer', 'Spring', 'Cool', 'HSV', 'Pink', 'Hot', 'Parula'};
img = cell2mat(cellfun(@(cmap) ...
    cv.applyColorMap(repmat(uint8(0:255), 20, 1), cmap), cmaps(:), ...
    'UniformOutput',false));
image(img)
set(gca, 'YTick', 10:20:20*numel(cmaps), 'YTickLabel',cmaps)
title('Colormaps')