So, how do you decide between JPG vs. PNG for your project? The answer depends on your needs. Because photography is almost always dealing with high-frequency images, filled with the types gradients and fine details that real-life object has, and that our brain's own filtering methods evolved for, JPEG makes the most common choice for photos.
There are exceptions to that rule, of course. One problem with lossy compression is that if you will be opening it and then saving it in a lossy format again, you've just doubled your loss. This means that lossy file formats degrade each time you open them and then save them. Keep in mind that multiple saves of the same open file will not cause this to occur. It is the act of saving and then reopening that will trigger the additional loss. If you plan on doing multiple edits of the same file, take this into consideration.
If your image is a drawing, which will have lots of spaces with solid colors, or even a photograph with a fair amount of text overlayed on it that also has large amounts of solid colors, then you are going to want to opt for PNG. As we mentioned in the lossy vs. lossless section, lossy formats such as JPEG lose their quality when large spaces of solid color are used.
If you need a format for printing and your printer supports the RGB color space, then most of the same recommendations for JPG or PNG apply as they do above. Typically for print, the question of JPEG vs. PNG isn't relevant, as professionals will use a higher quality format such as TIFF or PSD.
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