MATLAB: How to change the black color into transparency in png format

image processingtransparency

colorImage = imread('13100.png');
grayImage = rgb2gray(colorImage);
mserRegions = detectMSERFeatures(grayImage);
mserRegionsPixels = vertcat(cell2mat(mserRegions.PixelList));
mserMask = false(size(grayImage));
ind = sub2ind(size(mserMask), mserRegionsPixels(:,2), mserRegionsPixels(:,1));
mserMask(ind) = true;
f=figure();imshow(mserMask,'Border','tight');
maskedimage = immultiply(colorImage, repmat(mserMask, [1, 1, size(colorImage, 3)]));
imshow(maskedimage,'Border','tight');
TransparencyMaskedImage = maskedimage;
TransparencyMaskedImage(repmat(~mserMask, 1, 1, 3)) = ??;
imshow(TransparencyMaskedImage,'Border','tight');

Best Answer

To just write it transparent with imwrite, you do not need any of the three lines

TransparencyMaskedImage = maskedimage;
TransparencyMaskedImage(repmat(~mserMask, 1, 1, 3)) = ??;
imshow(TransparencyMaskedImage,'Border','tight');

instead,

imwrite(maskedimage, 'YourFileName.png', 'Transparency', [0 0 0]);

If you want to display the image with transparency, then

   mask = double( any(maskedimage, 3) );
   image(maskedimage, 'AlphaData', mask )    %notice this is not imshow

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MATLAB: How to retrieval back the color in particular area from original image

Much simpler:

maskedimage = immultiply(colorImage, repmat(mserMask, [1, 1, size(colorImage, 3)]));
imshow(maskedimage);

Note that if you just want to see if your mask is correct

imshowpair(colorImage, mserMask, 'blend');
 may be more useful.

MATLAB: How to include a colorbar for an RGB image overlayed with a black & white image

The missing lines are just being subsampled away when you go to display. They're still in the image, just use the magnifying glass to zoom in and you'll see them.

How about this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
image1 = imread('image1.jpg');
% Get the dimensions of the image.  
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(image1);
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Use weighted sum of ALL channels to create a gray scale image.
  image1 = rgb2gray(image1); 
  % ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
  % which in a typical snapshot will be the least noisy channel.
  % grayImage = grayImage(:, :, 2); % Take green channel.
end
% This image is supposed to be binary.
image1 = image1 > 128;
imshow(image1);
hp = impixelinfo();
% Display the image.

subplot(2, 2, 1);
imshow(image1, []);
axis on;
hold on;
title('Image1', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hold on
image2 = imread('image2.jpg');
% Display the image.
subplot(2, 2, 2);
imshow(image2, []);
hp = impixelinfo();
axis on;
hold on;
title('Image2', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
h3 = subplot(2, 2, 3:4);
% Mask the image using bsxfun() function
% maskedRgbImage = bsxfun(@times, image2, cast(image1, 'like', image2));
imshow(image1, []);
hp = impixelinfo();
hold on;
h=imshow(image2);
set(h,'Alphadata', 0.6);
axis on;
theColorMap = jet(256);
theColorMap(1,:) = 0; % First row is black.
theColorMap(end,:) = 1; % last row is white.
colormap(h3, theColorMap);
colorbar(h3);
caxis([0,0.6]);
title('Image1 with Image2 in overlay', 'FontSize', fontSize, 'Interpreter', 'None');
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0.05, 1, .95]);
% 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')

Best Answer

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MATLAB: How to retrieval back the color in particular area from original image

MATLAB: How to include a colorbar for an RGB image overlayed with a black & white image

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