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> However, here the author seems to accidentally fully recompress the images, and falls into the classic trap of "looks almost the same but the file is much sma
by vanderZwan 2y ago
> However, here the author seems to accidentally fully recompress the images, and falls into the classic trap of "looks almost the same but the file is much smaller!"
Except they didn't quite do that: yes, they recompressed the image instead of using the lossles rotation that JPEG is capable of. However, they then compared a recompressed rotated image to a recompressed image that wasn't rotated, and noted there was still a significant size differnce.
He also claims to have verified in GIMP that the two recompressed files were visually identical after rotating (I'm a little suspicious of that bit, since you wouldn't notice a tiny difference unless you use the "difference" layer mode and theo manually amplify the miniscule differences with something like the curves tool)
- sotix 2y agoYes this is the crux and the fun of my discovery! I was surprised how using sips to rotate the image resulted in a lower size than using sips or ImageMagick to directly compress the image. I’d encourage you to download the image from the link in the article and try yourself if you have a Mac and then compare them with GIMP because it’s very possible I didn’t do a perfect job with that.
- lifthrasiir 2y agoSee my other comment for the result from ImageMagick, which shows little difference regardless of the orientation. For sips, there is a possibility that chroma subsampling impacted the result (because there are two different scaling factors for each axis) and you are technically comparing different images.