Reduce the size of images even further by reducing number of colors with Gimp

In Gimp you go to Image in the top menu bar and select Mode followed by Indexed. Now you see a popup where you can select the number of colors for a generated optimum palette.

You’ll have to experiment a little because it will depend on your image.

I used this approach to shrink the size of the cover image in the_zopfli post from a 37KB (JPG) to just 15KB (PNG, all PNG sizes listed include Zopfli compression btw).

Straight JPG to PNG conversion: 124KB

PNG version RGB colors

First off, I exported the JPG file as a PNG file. This PNG file had a whopping 124KB! Clearly there was some bloat being stored.

256 colors: 40KB

Reducing from RGB to only 256 colors has no visible effect to my eyes.

256 colors

128 colors: 34KB

Still no difference.

128 colors

64 colors: 25KB

You can start to see some artifacting in the shadow behind the text.

64 colors

32 colors: 15KB

In my opinion this is the sweet spot. The shadow artifacting is barely noticable but the size is significantly reduced.

32 colors

16 colors: 11KB

Clear artifacting in the text shadow and the yellow (fire?) in the background has developed an outline.

16 colors

8 colors: 7.3KB

The broom has shifted in color from a clear brown to almost grey. Text shadow is just a grey blob at this point. Even clearer outline developed on the yellow background.

8 colors

4 colors: 4.3KB

Interestingly enough, I think 4 colors looks better than 8 colors. The outline in the background has disappeared because there’s not enough color spectrum to render it. The broom is now black and filled areas tend to get a white separator to the outlines.

4 colors

2 colors: 2.4KB

Well, at least the silhouette is well defined at this point I guess.

2 colors

Other posts in the Migrating from Ghost to Hugo series: