87 lines
2.1 KiB
Go
87 lines
2.1 KiB
Go
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// Copyright 2017 The goimagehash Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package goimagehash
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import (
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"errors"
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"image"
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"github.com/corona10/goimagehash/etcs"
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"github.com/corona10/goimagehash/transforms"
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"github.com/nfnt/resize"
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)
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// Average Hash computation.
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// Return 64bits hash.
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// Implementation follows
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// http://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html
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func AverageHash(img image.Image) (*ImageHash, error) {
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if img == nil {
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return nil, errors.New("Image object can not be nil.")
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}
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// Create 64bits hash.
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ahash := NewImageHash(0, AHash)
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resized := resize.Resize(8, 8, img, resize.Bilinear)
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pixels := transforms.Rgb2Gray(resized)
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flattens := transforms.FlattenPixels(pixels, 8, 8)
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avg := etcs.MeanOfPixels(flattens)
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for idx, p := range flattens {
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if p > avg {
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ahash.Set(idx)
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}
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}
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return ahash, nil
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}
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// Difference Hash computation.
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// Implementation follows
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// http://www.hackerfactor.com/blog/?/archives/529-Kind-of-Like-That.html
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func DifferenceHash(img image.Image) (*ImageHash, error) {
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if img == nil {
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return nil, errors.New("Image object can not be nil.")
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}
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dhash := NewImageHash(0, DHash)
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resized := resize.Resize(9, 8, img, resize.Bilinear)
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pixels := transforms.Rgb2Gray(resized)
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idx := 0
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for i := 0; i < len(pixels); i++ {
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for j := 0; j < len(pixels[i])-1; j++ {
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if pixels[i][j] < pixels[i][j+1] {
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dhash.Set(idx)
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}
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idx++
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}
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}
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return dhash, nil
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}
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// Perceptual Hash computation.
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// Implementation follows
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// http://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html
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func PerceptionHash(img image.Image) (*ImageHash, error) {
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if img == nil {
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return nil, errors.New("Image object can not be nil")
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}
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phash := NewImageHash(0, PHash)
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resized := resize.Resize(64, 64, img, resize.Bilinear)
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pixels := transforms.Rgb2Gray(resized)
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dct := transforms.DCT2D(pixels, 64, 64)
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flattens := transforms.FlattenPixels(dct, 8, 8)
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median := etcs.MedianOfPixels(flattens)
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for idx, p := range flattens {
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if p > median {
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phash.Set(idx)
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}
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}
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return phash, nil
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}
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