Image:Phalaenopsis JPEG.png

[edit] Summary

A picture of a flower (Phalaenopsis_(aka).jpg by André Karwath) compressed with successively higher loss JPEG compression ratios from left to right by User:Ilmari_Karonen. Re-done in PNG format by User:brianski to avoid some double-compression artifacts (particularly in the detailed center and blocky right parts of the image).

[edit] Technical details

The image was produced by first scaling down the original picture in the GIMP and using ImageMagick convert to cut it into 8 pixel wide slices, which were each compressed at different quality levels using Perl and cjpeg and recombined with ImageMagick montage. The exact commands used were:

$ convert -crop 8x214 +adjoin Phalaenopsis_\(aka\).240x214.png Phalaenopsis_test_%02d.ppm
$ perl -e 'for $n (0..29) { system sprintf "cjpeg -optimize -sample 1x1 -dct float -quality %f Phalaenopsis_test_%02d.ppm
  >Phalaenopsis_test_%02d.jpg", 2+78*(1-$n/29)**2.3, $n, $n;}'
$ montage +frame +shadow +label -tile 30x1 -geometry 8x214+0+0 -quality 80 Phalaenopsis_test_??.jpg Phalaenopsis_JPEG.png

The expression 2+78*(1-$n/29)**2.3 produces a nonlinear quality gradient from 80% down to 2% quality. The exponent was chosen by trial and error to yield a nice looking image with a good balance of high and low quality areas.

[edit] Licensing

I, the copyright holder of this work, hereby publish it under the following license: This file is licensed under the Creative Commons Attribution ShareAlike 2.5 License. In short: you are free to share and make derivative works of the file under the conditions that you appropriately attribute it, and that you distribute it only under a license identical to this one. Official license

http://commons.wikimedia.org/wiki/

• JPEG