ImageMagick: scale JPEG image with a maximum file-size

Question

I have a number of JPEG pictures which I would like to scale down. Another requirement is that the file size should not be larger than say 300kByte.

Is that possible

Answer 1

To restrict the resulting image to a maximum file size, you can use the commandline parameter -define jpeg:extent=max_value, like this:

convert original.jpeg -define jpeg:extent=300kb output.jpg
convert original.jpeg -define jpeg:extent=300kb -scale 50% output.jpg
convert original.jpeg -define jpeg:extent=300kb [...other options...] output.jpg

Note, this will not always work to match the exact size you wanted. You may have asked for 40kb output size, where input is 300kb, and get a result of 48kb.

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(Update/Clarification: Output file size may be a bit lower or higher than your file requested size.)