Compress png images with Gimp
I'm getting a message from PageSpeed Insights that recommends to compress some
png images. E.g:
If compressing .../logo.png without loosing information, you would save 1.014 B (12% redcuction).
However, I've compressed the image with "Save for web" option and with the maximum compression. Tried to compress more times, but the image is never compressed more than about 200B. I could compress with PNG-8, but then I'm loosing image quality.
All other formats seem to be well compressed by Gimp with the same option. Any idea of why it's happening and how to solve it?
GIMP is quite good in PNG compression, but not the best.
To get a basic idea about PNG optimization, read File size and optimization software chapter in "Portable Network Graphics" article on Wikipedia.
I have optimized thousands of PNGs and I recommend these tools for a lossless optimization: PNGOUT, ZopfliPNG.
If you want to make your files even smaller, consider conversion from RGB to indexed, using pngquant. It is lossy but still gives very good results. After this conversion, do the optimization with PNGOUT or ZopfliPNG.