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Q&A

Comments on How to decrease image size from commandline

Post

How to decrease image size from commandline

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Problem

I'd like to be able to decrease images, particularly jpg and png's, either to a percentage of the original file, or a specified size in bytes.

MWE

decrease --size=900KB -o image_small.png image.png
decrease --size=90% -o image_small.png image.png

Notes

It can be two separate tools, but I want them to support both options, and ideally, follow proper Unix option dash conventions (--out=file, -o file).

For jpg, I found jpegoptim which allows me to specify a size in either kilobytes or percentage:

jpegoptim --size=900 --dest=compressed image.jpg
jpegoptim --size=90% --dest=compressed image.jpg

One downside of this though is it does not have a -o option to create a new file; it either overwrites the input file, or takes in an output directory that must exist ahead of time.

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1 comment thread

What does "size" mean in this context? (2 comments)
What does "size" mean in this context?
ArrayBolt3‭ wrote over 1 year ago

By "size", do you mean image resolution or file size? If you mean image resolution, there's probably good tools for that. File size might be trickier, though I don't know for sure. I think you mean file size.

manassehkatz‭ wrote 11 months ago

To clarify a little more: Size can be resolution and size can be file size. JPG is a lossy compressed format, so it is (generally) possible to change the resolution to make the file smaller while keeping the same quality level or change the quality level. With a format such as PNG, you can change the resolution but because the compression is lossless you can't do anything about that - i.e., you can't lower the quality to get a smaller file because the quality is always 100% of the original.