phash

README

phash

A simple Go package to calculate a phash of an image.

Documentation

Overview

Package phash computes a perceptual hash of an image.

Hash values are highly dependent on the scaling function used.

Index

• func Distance(h1, h2 uint64) int
• func Get(img image.Image, scalefunc ScaleFunc) (uint64, error)
• type ScaleFunc

Functions

func Distance

func Distance(h1, h2 uint64) int

Distance distance between two hashes (number of bits that differ)

func Get

func Get(img image.Image, scalefunc ScaleFunc) (uint64, error)

Get calculates perceptual hash for an image. It uses scalefunc to scale image to 32×32 size if needed.

Types

type ScaleFunc

type ScaleFunc func(img image.Image, width, height int) image.Image

ScaleFunc is a function Get uses to scale image to a 32×32 if needed.

An example of a ScaleFunc, using github.com/disintegration/imaging package:

scalefunc := func(img image.Image, w, h int) image.Image {
    return imaging.Resize(img, w, h, imaging.Lanczos)
}

Note that hash value depends highly on a scaling algorithm, smoother scaling algorithms usually work better.

Function must return a 32×32 image with its top left point having 0, 0 coordinates.