imshow displays black instead of transparent background of png image

Question

Denis Perotto 2024-2-7

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2079116-imshow-displays-black-instead-of-transparent-background-of-png-image

评论： Joshua 2024-3-22

I need to display a .png image that has transparent background in a figure. I also need to change the transparency of its solid part. I tried to do it using imshow like this:

figure
hold on
plot([1 2], [1 2])
axes("pos",[.1 .1 .1 .1])
foo = imshow("some_image.png");
foo.AlphaData = 0.8;

The problem is that the transparent background of my .png becomes solid black on figure. How to fix it?

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Answer 1

Walter Roberson 2024-2-7

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https://ww2.mathworks.cn/matlabcentral/answers/2079116-imshow-displays-black-instead-of-transparent-background-of-png-image#answer_1404176

在 MATLAB Online 中打开

figure
hold on
plot([1 2], [1 2])
axes("pos",[.1 .1 .1 .1])
[myimage, cmap, alpha] = imread("some_image.png");
foo = imshow(myimage, cmap);
foo.AlphaData = alpha;

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Denis Perotto 2024-2-7

在 MATLAB Online 中打开

Thanks, it works, except for the last line should be

foo.AlphaData = 0.8 .* alpha;

Joshua 2024-3-22

@Walter Roberson

I would like to thank you for all of your responses throughout the years. I am new to MATLAB, but not new to coding, and you have made learning this language exponentially easier with your consistent, accurate tips. Your comment here is just +1 to the massive amount of times you have helped me in my project. Take care!

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