johansatge/jpeg-autorotate

is quality 100 the same as lossless?

Offirmo opened this issue · 2 comments

Offirmo commented

This module looks awesome and I'd like to use it to sort my billion photos.

However, I'm concerned in the loss of quality in my pictures. I know that the JPG format allows lossless rotation (https://www.betterjpeg.com/lossless-rotation.htm)

Is it what your module does? Or does your module rotate the full bit plane then re-encode?

johansatge commented

Hi,

the rotation will not be lossless unfortunately, no matter the selected quality.

If you configure quality: 100 you will probably end up with a bigger image than the original (this is a known issue with jpeg-js, the decoder/encoder used in this project.)

If you plan on using the tool on a big number of images, I can only encourage you to make backups and try different qualities to find the more relevant one for your use case :)

Offirmo commented

Thanks for the answer.

I couldn't find a lossless rotate on npm so far, will keep looking.

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