I am encrypting an image and displaying the encrypted image and also saving it in the default directory with a .jpeg extension. It displays the image fine and even reads the image using imread() but if I try to open the file that got saved I get a message that the format is not supported. Why is this happening?
MATLAB: Image created but not of supported file type
image
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imwrite(encrimage,'eimage.jpeg', 'mode', 'lossless');However, as soon as someone does not notice that it needs to be a lossless JPEG and "helpfully" re-saves it, your program would fail again.
Lesson: Don't use JPEG for storing data.
If you are required to use JPEG for storing data then you need to do the DCT yourself, work with the values obtained, make whatever changes, and do an inverse DCT on that -- so that when you imwrite() the file, the DCT that it does automatically will end up with the data you want to store.
Try this, and note that the sizes are the same:
rgbImage = imread('peppers.png');ROI = roipoly(rgbImage); % Select a closed polygon
subplot(3, 1, 1);imshow(rgbImage);axis('on', 'image');title('Original Image');% Mask the image using bsxfun() function to multiply the mask by each channel individually.
maskedRgbImage = bsxfun(@times, rgbImage, cast(ROI, 'like', rgbImage));whos maskedRgbImage% Display the masked image.
subplot(3, 1, 2);imshow(maskedRgbImage);axis('on', 'image');title('Masked Image');% Save the masked image to disk.
imwrite(maskedRgbImage, 'newImage.png');I2 = imread('newImage.png');whos I2% Display the image read in from disk.
subplot(3, 1, 3);imshow(I2);axis('on', 'image');title('Image read In From Disk');
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