d68e89bd8f
* gitignore *.html for test coverage reports * fix typos * Increase hashcompute.go test coverage to 100 percent * Add new Go versions. Upgrade GitHub Actions. * Add tests for missing ext hashes * Add test for hashing non-hexadecimal string * Add tests for loading empty bytes buffer * Run go fmt * Fix comments * Fix comments * Fix spelling * fix actions versions * Upgrade to actions/setup-go@v4 * Add minimum Go version for go.mod
100 lines
2.6 KiB
Go
100 lines
2.6 KiB
Go
// 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 transforms
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import (
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"image"
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)
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// Rgb2Gray function converts RGB to a gray scale array.
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func Rgb2Gray(colorImg image.Image) [][]float64 {
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bounds := colorImg.Bounds()
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w, h := bounds.Max.X-bounds.Min.X, bounds.Max.Y-bounds.Min.Y
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pixels := make([][]float64, h)
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for i := range pixels {
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pixels[i] = make([]float64, w)
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for j := range pixels[i] {
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color := colorImg.At(j, i)
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r, g, b, _ := color.RGBA()
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lum := 0.299*float64(r/257) + 0.587*float64(g/257) + 0.114*float64(b/256)
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pixels[i][j] = lum
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}
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}
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return pixels
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}
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// Rgb2GrayFast function converts RGB to a gray scale array.
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func Rgb2GrayFast(colorImg image.Image, pixels *[]float64) {
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bounds := colorImg.Bounds()
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w, h := bounds.Max.X-bounds.Min.X, bounds.Max.Y-bounds.Min.Y
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if w != h {
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return
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}
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switch c := colorImg.(type) {
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case *image.YCbCr:
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rgb2GrayYCbCR(c, *pixels, w)
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case *image.RGBA:
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rgb2GrayRGBA(c, *pixels, w)
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default:
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rgb2GrayDefault(c, *pixels, w)
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}
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}
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// pixel2Gray converts a pixel to grayscale value base on luminosity
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func pixel2Gray(r, g, b, a uint32) float64 {
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return 0.299*float64(r/257) + 0.587*float64(g/257) + 0.114*float64(b/256)
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}
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// rgb2GrayDefault uses the image.Image interface
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func rgb2GrayDefault(colorImg image.Image, pixels []float64, s int) {
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for i := 0; i < s; i++ {
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for j := 0; j < s; j++ {
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pixels[j+(i*s)] = pixel2Gray(colorImg.At(j, i).RGBA())
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}
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}
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}
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// rgb2GrayYCbCR uses *image.YCbCr which is significantly faster than the image.Image interface.
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func rgb2GrayYCbCR(colorImg *image.YCbCr, pixels []float64, s int) {
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for i := 0; i < s; i++ {
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for j := 0; j < s; j++ {
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pixels[j+(i*s)] = pixel2Gray(colorImg.YCbCrAt(j, i).RGBA())
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}
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}
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}
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// rgb2GrayRGBA uses *image.RGBA which is significantly faster than the image.Image interface.
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func rgb2GrayRGBA(colorImg *image.RGBA, pixels []float64, s int) {
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for i := 0; i < s; i++ {
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for j := 0; j < s; j++ {
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pixels[(i*s)+j] = pixel2Gray(colorImg.At(j, i).RGBA())
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}
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}
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}
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// FlattenPixels function flattens 2d array into 1d array.
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func FlattenPixels(pixels [][]float64, x int, y int) []float64 {
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flattens := make([]float64, x*y)
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for i := 0; i < y; i++ {
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for j := 0; j < x; j++ {
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flattens[y*i+j] = pixels[i][j]
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}
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}
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return flattens
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}
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// FlattenPixelsFast64 function flattens 2d array into 1d array.
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func FlattenPixelsFast64(pixels []float64, x int, y int) []float64 {
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flattens := [64]float64{}
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for i := 0; i < y; i++ {
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for j := 0; j < x; j++ {
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flattens[y*i+j] = pixels[(i*64)+j]
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}
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}
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return flattens[:]
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}
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