I’ve been writing a lot about images on the web lately, but I haven’t mentioned PNG format, or when PNG might be a better alternative to its lossy counterparts.

Because PNG is a lossless format, it holds up much better to being scaled up, decoded/re-encoded, and modified, so it’s worth taking a look at.

Obviously PNGs are good for transparency. SVG also offers transparency, but will quickly bloat as the complexity of the image increases. I ran some simple tests to find out if and when PNG is probably good choice for non-transparent images.

The Portable Networks Graphic (PNG) compression algorithm was actually created as a replacement for GIF, which was patented and controlled by a large tech company. Open-source wins again!

Test results (all values in kb)

All values shown in kilobytes (kb). Winners indicated for each test.

Application JPG (no compression) PNG PNG-8 SVG
Logo Wordmark 40 7 4 8
Flat Pattern 152 35 17 26
Paragraph Text 123 18 10 21
Small Photo 186 285 129 1327
Large Photo 1,224 2,742 1,317 1,327

Takeaways

1. PNGs work well for flat designs

Flat designs like patterns and typography are a great application for PNG images. These compress well, and may in some cases be smaller than SVG. If it’s a simple logo, SVG is probably a better option, because vectors.

2. 8-bit is better

In this simple study, 8-bit PNGs averaged 49% smaller than ordinary 24-bit PNGs. This was a significant reduction in the size of the image. Even with less colors, there wasn’t a noticable difference in visual quality.


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