92 lines
1.9 KiB
Go
92 lines
1.9 KiB
Go
package colors
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type LightMap []Luminance
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// Hex returns all luminance value as a hex encoded string.
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func (m LightMap) Hex() (result string) {
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for _, luminance := range m {
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if luminance > 15 {
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result += "F"
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} else {
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result += luminance.Hex()
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}
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}
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return result
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}
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type diffValue struct {
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a []int
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b []int
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}
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// Pixel comparisons for calculating the diff value.
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var diffValues = []diffValue{
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{a: []int{4, 4, 4, 4}, b: []int{1, 3, 5, 7}},
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{a: []int{0}, b: []int{1}},
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{a: []int{0}, b: []int{3}},
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{a: []int{2}, b: []int{1}},
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{a: []int{2}, b: []int{5}},
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{a: []int{6}, b: []int{3}},
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{a: []int{6}, b: []int{7}},
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{a: []int{8}, b: []int{5}},
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{a: []int{8}, b: []int{7}},
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}
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/*
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Alternative values to experiment with:
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{a: []int{4, 4, 4, 4}, b: []int{1, 3, 5, 7}},
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{a: []int{0}, b: []int{2}},
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{a: []int{8}, b: []int{6}},
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{a: []int{0}, b: []int{1}},
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{a: []int{1}, b: []int{2}},
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{a: []int{2}, b: []int{5}},
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{a: []int{8}, b: []int{7}},
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{a: []int{7}, b: []int{6}},
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{a: []int{5}, b: []int{8}},
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{a: []int{6}, b: []int{3}},
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Other ideas:
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- Use Lightness instead of luminance
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- Use more pixels (difficult as we only have 3x3 thumbs right now)
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- Iterative calculation using smaller offsets for each round (current offset is +4)
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For a more complex implementation, see
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https://github.com/EdjoLabs/image-match/blob/master/image_match/goldberg.py
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http://www.cs.cmu.edu/~hcwong/Pdfs/icip02.ps
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General blog post on Perceptual image hashing:
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https://jenssegers.com/perceptual-image-hashes
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*/
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// Diff returns an integer that can be used to find similar images.
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func (m LightMap) Diff() (result int) {
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if len(m) != 9 {
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return 0
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}
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result = 1
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for _, val := range diffValues {
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result = result << 1
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a := 0
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b := 0
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for _, i := range val.a {
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a += int(m[i])
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}
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for _, i := range val.b {
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b += int(m[i])
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}
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if a+4 > b {
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result += 1
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}
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}
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return result
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}
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