MATLAB: Is it possible to plot a spectrogram of a wav file in just red color

digital image processingimage processingspectrogram

I know how to plot a spectrogram in different formats like jet, grayscale hsv etc. But I was wondering if its possible to plot a spectrogram of a wav file in just red colour or in green colour or in blue colour.

I have attached a screenshot to show an example. I made this by saving the original spectrogram in png format and converting it into Red, green and blue colour using usual image processing technique.

Best Answer

Couldn't you just create your own colormap that varies along one RGB column while the other two columns have a constant color such as black? Here's an example using the red axis.

colorMap = [linspace(0,1,256)', zeros(256,2)]
colormap(colorMap);

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MATLAB: Fake colorbar for image

Do you mean like this:

% Read in the color demo image.
[rgbImage, colorMap] = imread('peppers.png');
imshow(rgbImage, colorMap);
axis on;
title('Original Color Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
drawnow;
% 'Red Pepper' [194 24 25], 'Green Pepper' [114 24 55], 'Purple Cloth' [117 74 26], and 'White Garlic' [255 255 255].
cMap = [194 24 25;114 24 55; 117 74 26; 255 255 255]/255
colormap(cMap);
colorbar('Ticks',32:64:255,...
  'TickLabels',{'Red Pepper','Green Pepper','Purple Cloth','White Garlic'},...
  'FontSize', 20);

I think your color definitions are strange though. Purple and green seem switched.

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ax = gca;   %or as appropriate
yticklabels = get(ax, 'YTickLabel');
yticklabels{end} = '';   %needs to exist but make it empty
set(ax, 'YTickLabel', yticklabels);

Best Answer

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