MATLAB: Open a transparent png and a jpg background together on a single graphical window

.jpggraphicsimage processingpngtransparency

Hello everyone,

I have 2 images. One is a normal jpg image (i.e. Background) and another is a .png image with the transparency. I want to open this transparent png on jpg image such that it looks like given below:

1. jpg image:

2. transparent png image:

Now, the output should look like:

(Note: You can see that the transparency is maintained in output image.)

Can anyone help me? (These images are just for giving clear explanation of my problems. Actual images are similar to them.)

Thanks in advance.

Best Answer

bgimage = imread('e8b66924592e1115398fe4a53bd6415c.jpg');
imshow(bgimage);
hold on;     %so the second image is displayed on top of the first
[fgimage, ~, alpha]  = imread('Abstract-Circular-Design.png');
hfg = imshow(fgimage);
hfg.AlphaData = alpha;    %set transparency
hfg.XData = [100 500];   %change position and size as appropriate
hfg.YData = [100 500];

Related Solutions

MATLAB: Resize and save transparent PNG file in matlab

For a start you never retrieve the transparency information so it's no wonder it's not preserved.

PNG images have two ways to specify transparency. For grayscale and true colour images, the transparency can be specified as an additional alpha channel the same size as the image. You get that in matlab from the 3rd output of imread (not the 2nd). Indexed images in PNG cannot have an alpha channel

For all types of images (so grayscale, true colour and indexed), PNG also allows you to specify a specific colour as transparent. To get that transparent colour in matlab you have to use at the SimpleTransparencyData field of imfinfo.

Assuming your image is actually true colour and that your code is a mistake, then:

[im, ~, alpha] = imread('image.png');  %transparency not valid for index images, so no point in getting map
im2 = imresize(im, [200, 200]);
alpha2 = imresize(alpha, [200 200]);
imwrite(im2, 'image2.png');

If the transparency is actually the second type ( imfinfo will have 'simple' for the Transparency field, then:

fileinfo = imfinfo('image.png');
assert(strcmp(fileinfo.Transparency, 'simple'), 'This file does not have simple transparency')
im = imread('image.png');  %if image is actually indexed, you also need to retrieve the colour map
im2 = imresize(im, [200 200]);
imwrite(im2, 'image2.png', 'Transparency', fileinfo.SimpleTransparencyData);

However, in that second case, note that because of the default interpolation, some transparent pixel may get assigned a colour that is no longer transparent. Using the non-default 'nearest' interpolation option in imresize would solve that problem.

MATLAB: How to find the inner contour of the theocardium

Assuming you can start with that cropped image, just threshold for that gray scale range, then get rid of blobs touching the border with imclearborder(), then fill with imfill(), then extract the largest blob using the function in my attached demo.

Best Answer

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MATLAB: Resize and save transparent PNG file in matlab

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