82 lines
1.7 KiB
Go
82 lines
1.7 KiB
Go
// Package vision 提供帧差指纹、图片编码与（可选的）本地检测接口。
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package vision
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import (
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"image"
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"golang.org/x/image/draw"
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)
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// Fingerprint 是用于判断"画面有没有变化"的感知哈希。
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type Fingerprint struct {
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AHash uint64 // 均值哈希
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DHash uint64 // 差分哈希
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Mean uint8 // 平均亮度
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}
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// grayGrid 把图像缩放到 w×h 的灰度图。
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func grayGrid(src image.Image, w, h int) *image.Gray {
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dst := image.NewGray(image.Rect(0, 0, w, h))
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draw.ApproxBiLinear.Scale(dst, dst.Bounds(), src, src.Bounds(), draw.Src, nil)
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return dst
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}
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// Of 计算图像指纹。
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func Of(img image.Image) Fingerprint {
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if img == nil {
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return Fingerprint{}
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}
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small := grayGrid(img, 8, 8)
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var sum, n int
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for _, v := range small.Pix {
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sum += int(v)
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n++
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}
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avg := sum / max(n, 1)
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mean := uint8(min(avg, 255))
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var aHash uint64
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for i, v := range small.Pix {
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if int(v) > avg {
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aHash |= 1 << uint(i)
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}
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}
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wide := grayGrid(img, 9, 8)
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var dHash uint64
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for y := 0; y < 8; y++ {
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for x := 0; x < 8; x++ {
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l := wide.GrayAt(x, y).Y
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r := wide.GrayAt(x+1, y).Y
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if l > r {
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dHash |= 1 << uint(y*8+x)
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}
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}
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}
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return Fingerprint{AHash: aHash, DHash: dHash, Mean: mean}
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}
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// Distance 返回两个指纹的汉明距离（取两种哈希的较大值，偏向灵敏）。
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func (f Fingerprint) Distance(o Fingerprint) int {
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return max(bitsSet(f.AHash^o.AHash), bitsSet(f.DHash^o.DHash))
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}
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// Changed 判断画面是否发生了足以触发提问的变化。
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func (f Fingerprint) Changed(o Fingerprint, threshold int) bool {
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if threshold <= 0 {
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threshold = 5
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}
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return f.Distance(o) > threshold
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}
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func bitsSet(v uint64) int {
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n := 0
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for v != 0 {
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v &= v - 1
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n++
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}
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return n
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}
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