91 lines
2.3 KiB
Go
91 lines
2.3 KiB
Go
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package service
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import (
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"image"
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"math"
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)
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type rotate struct {
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dx float64
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dy float64
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sin float64
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cos float64
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neww float64
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newh float64
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src *image.RGBA
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}
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func (r *rotate) rotate(angle float64, src *image.RGBA) *rotate {
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r.src = src
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srsize := src.Bounds().Size()
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width, height := srsize.X, srsize.Y
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// 源图四个角的坐标（以图像中心为坐标系原点）
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// 左下角,右下角,左上角,右上角
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srcwp, srchp := float64(width)*0.5, float64(height)*0.5
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srcx1, srcy1 := -srcwp, srchp
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srcx2, srcy2 := srcwp, srchp
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srcx3, srcy3 := -srcwp, -srchp
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srcx4, srcy4 := srcwp, -srchp
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r.sin, r.cos = math.Sincos(radian(angle))
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// 旋转后的四角坐标
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desx1, desy1 := r.cos*srcx1+r.sin*srcy1, -r.sin*srcx1+r.cos*srcy1
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desx2, desy2 := r.cos*srcx2+r.sin*srcy2, -r.sin*srcx2+r.cos*srcy2
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desx3, desy3 := r.cos*srcx3+r.sin*srcy3, -r.sin*srcx3+r.cos*srcy3
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desx4, desy4 := r.cos*srcx4+r.sin*srcy4, -r.sin*srcx4+r.cos*srcy4
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// 新的高度很宽度
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r.neww = math.Max(math.Abs(desx4-desx1), math.Abs(desx3-desx2)) + 0.5
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r.newh = math.Max(math.Abs(desy4-desy1), math.Abs(desy3-desy2)) + 0.5
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r.dx = -0.5*r.neww*r.cos - 0.5*r.newh*r.sin + srcwp
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r.dy = 0.5*r.neww*r.sin - 0.5*r.newh*r.cos + srchp
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return r
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}
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func radian(angle float64) float64 {
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return angle * math.Pi / 180.0
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}
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func (r *rotate) transformRGBA() image.Image {
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srcb := r.src.Bounds()
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b := image.Rect(0, 0, int(r.neww), int(r.newh))
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dst := image.NewRGBA(b)
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for y := b.Min.Y; y < b.Max.Y; y++ {
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for x := b.Min.X; x < b.Max.X; x++ {
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sx, sy := r.pt(x, y)
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if inBounds(srcb, sx, sy) {
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// 消除锯齿填色
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c := bili.RGBA(r.src, sx, sy)
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off := (y-dst.Rect.Min.Y)*dst.Stride + (x-dst.Rect.Min.X)*4
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dst.Pix[off+0] = c.R
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dst.Pix[off+1] = c.G
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dst.Pix[off+2] = c.B
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dst.Pix[off+3] = c.A
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}
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}
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}
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return dst
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}
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func (r *rotate) pt(x, y int) (float64, float64) {
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return float64(-y)*r.sin + float64(x)*r.cos + r.dy,
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float64(y)*r.cos + float64(x)*r.sin + r.dx
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}
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func inBounds(b image.Rectangle, x, y float64) bool {
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if x < float64(b.Min.X) || x >= float64(b.Max.X) {
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return false
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}
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if y < float64(b.Min.Y) || y >= float64(b.Max.Y) {
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return false
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}
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return true
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}
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func offRGBA(src *image.RGBA, x, y int) int {
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return (y-src.Rect.Min.Y)*src.Stride + (x-src.Rect.Min.X)*4
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}
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