Compressed image still massive even with super low quality min/max.

[datermine]

I've been using pngquant successfully for sometime now, but I've noticed recently that some images are just not compressing very much.

In the below, I'm trying to compress f.png which is 3+mb, but the smallest I can get it with pngquant is 2.7mb.

I must be doing something wrong.

gmike@instance:~/projects/scratch/comp$ pngquant --version
2.5.0 (June 2015)
gmike@instance:~/projects/scratch/comp$ ls -ltr
total 6064
-rwxr-xr-x 1 gmike gmike    1658 Aug 31 18:58 compress_image_and_upload.sh
-rw-r--r-- 1 gmike gmike 3460607 Aug 31 18:58 f.png
-rw-r--r-- 1 gmike gmike 2741762 Aug 31 19:06 f.pngquant.png
gmike@instance:~/projects/scratch/comp$ pngquant -v --quality=5-20 --force --ext .pngquant.png ./f.png
./f.png:
  read 3380KB file
  made histogram...14319 colors found
  selecting colors...4%
  selecting colors...25%
  selecting colors...28%
  selecting colors...32%
  selecting colors...35%
  selecting colors...38%
  selecting colors...42%
  selecting colors...45%
  selecting colors...49%
  selecting colors...52%
  selecting colors...56%
  selecting colors...59%
  selecting colors...63%
  selecting colors...66%
  selecting colors...69%
  selecting colors...73%
  selecting colors...76%
  selecting colors...80%
  selecting colors...83%
  selecting colors...100%
  moving colormap towards local minimum
  eliminated opaque tRNS-chunk entries...0 entries transparent
  mapped image to new colors...MSE=20.650 (Q=42)
  writing 11-color image as f.pngquant.png
No errors detected while quantizing 1 image.
gmike@instance:~/projects/scratch/comp$ ls -ltr
total 6064
-rwxr-xr-x 1 gmike gmike    1658 Aug 31 18:58 compress_image_and_upload.sh
-rw-r--r-- 1 gmike gmike 3460607 Aug 31 18:58 f.png
-rw-r--r-- 1 gmike gmike 2741762 Aug 31 19:06 f.pngquant.png

[kornelski]

Try adding --strip to remove metadata.

If the image has lots of pixels, it may just be that big. Expect 0.5 byte per pixel.

[datermine]

I noticed --strip wasn't available. I'm on v2.5, but that's what I'm getting with sudo apt-get install pngquant.

Is there a better way to get v2.12