Closed guettli closed 2 years ago
$ jpegquality result-jpegoptim.jpg
jpegquality version 1.2
#File: result-jpegoptim.jpg
Quantization table
Precision=0; Table index=0 (luminance)
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
Estimated quality level = -155.00%
Quality too low; estimate may be incorrect.
Quantization table
Precision=0; Table index=1 (chrominance)
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
255 255 255 255 255 255 255 255
Estimated quality level = -155.00%
Quality too low; estimate may be incorrect.
Average quality: -155.00% (-154%:Poor)
:information_source: 255 - this is the limit.
@zvezdochiot please elaborate. What do you want to tell me with your comment?
Hi @guettli .
:information_source: The value 255
is the maximum in the quantization tables (see above). Quantization tables are a jpeg filtering mechanism. It is impossible to get more filtering with jpeg, and the file will not become smaller than this level.
My goal is the reduce the file size while keeping the image nice for the human eye.
I found a solution and published it here: https://github.com/guettli/cheat-sheet/blob/master/README.md#reducing-image-size
convert image.jpg -resize '1000x>' -define jpeg:extent=100KB result.jpg
This reduced the resolution before reducing the jpg-size. The result is better than with jpegoptim
.