golang-png-encoding

README

Golang PNG Encoding

This repo test PNG compression parameters for Golang's image/png library.

Usage

You need dep and go install on your machine.

• To download the dependencies: dep ensure
• To build & run the program: go run main.go apercu-slack.png

Example output:

original image is 26297 bytes
decoded image: *image.Paletted, 1280x920px and 31368 bytes
resized image: *image.NRGBA, 1024x736px and 47339 bytes
indexed image: *image.Paletted, 1024x736px and 23617 bytes
compressed image: *image.NRGBA, 1024x736px and 80984 bytes
indexed image: *image.Paletted, 1024x736px and 31352 bytes

Summary

• png.DefaultCompression gives the best result
• original image comes with a custom color palette
• reduced image lose the color palette
• image reduced with nearest neighbor have a smaller size:
  • indexed image with box: 26174 bytes
  • indexed image with nearest neighbor: 23617 bytes
  • compressed image with box: 98563 bytes
  • compressed image with nearest neighbor: 80984 bytes
• lossypng does not help to get back to the original size
• applying the original color palette to the reduced image is the best 💜

Images

Encoding	Image
Reduced
Reduced & Indexed
Reduced & Lossy
Reduced, Lossy & Indexed