New answers tagged image-compression
If a jpeg has been resaved as another jpeg, the file size will always change because the image will undergo lossy compression. I.e. when you lose some information, the size of the file will change because the image is now a tiny bit different. Did you apply any curves or levels to the image difference to exaggerate the difference between the two images?
The actual screen representation of a jpeg file (or any other graphic file) is different from the one which lies in the file. Because JPEG is a lossy compression, the JPEG cannot be converted BACK to the original bitmap (the one which was saved by camera and/or another program). It is converted to one (or more) new bitmap(s) which can be (and is) dependent ...
Yes. How else could it be displayed? The screen needs to show the actual pixels, not an abstracted mathematical representation of them. Perhaps more crucially, a JPEG needs to be converted to a bitmap to be edited, which is why re-saving an image in JPEG can cause artifacts and loss of detail even if you don't change anything.
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