02-20-2022, 09:50 PM
It is how they measure the image quality also the compression value is not equivalent between formats.
Quality ? Look up ssim. Using ImageMagick gives a ssim value
A comparison using a scanned in photo 300 ppi exported as a png for the reference image.
A 90% jpeg size 0.67 MB has a quality difference (ssim) 0.96 versus a 95% webp size 0.61 MB ssim 0.96
That end of the scale roughly equivalent here, a small saving on file size.
The other end of the scale 60% jpeg size 0.31 MB ssim 0.93 versus a 75% webp size 0.23 MB ssim 0.92
Roughly the same quality with a smaller file size, about a 25% saving.
It is a format for web use I'm not going to archive any photos with it.
Quality ? Look up ssim. Using ImageMagick gives a ssim value
Code:
magick compare -metric ssim ref-file compressed-file null:A comparison using a scanned in photo 300 ppi exported as a png for the reference image.
A 90% jpeg size 0.67 MB has a quality difference (ssim) 0.96 versus a 95% webp size 0.61 MB ssim 0.96
That end of the scale roughly equivalent here, a small saving on file size.
The other end of the scale 60% jpeg size 0.31 MB ssim 0.93 versus a 75% webp size 0.23 MB ssim 0.92
Roughly the same quality with a smaller file size, about a 25% saving.
It is a format for web use I'm not going to archive any photos with it.