feat(图像性能): 保留图像精度并加速缩放

ofdgo_image.go

@@ -426,6 +426,9 @@ func imageWithTransparentEdge(img image.Image) (image.Image, int) {
 	if opaque, ok := source.(interface{ Opaque() bool }); ok && opaque.Opaque() {
 		return img, 0
 	}
+	if model := source.ColorModel(); model == color.NRGBA64Model || model == color.RGBA64Model || model == color.Alpha16Model || model == color.Gray16Model {
+		return imageWithTransparentEdge64(img, source)
+	}
 	hasZero, hasVisible := false, false
 	src, ok := source.(*image.NRGBA)
 	if ok {
@@ -510,3 +513,81 @@ func (s *transparentEdgeImage) RGBA64At(x, y int) color.RGBA64 {
 	r, g, b, a := s.NRGBAAt(x, y).RGBA()
 	return color.RGBA64{R: uint16(r), G: uint16(g), B: uint16(b), A: uint16(a)}
 }
+
+// imageWithTransparentEdge64 保留十六位颜色和透明度，不经八位图像中转
+// 入参: original 原始图像, source 已解码的像素源
+// 返回: image.Image 边缘处理结果, int 补齐像素数
+func imageWithTransparentEdge64(original, source image.Image) (image.Image, int) {
+	bounds := source.Bounds()
+	hasZero, hasVisible := false, false
+	for y := bounds.Min.Y; y < bounds.Max.Y && !(hasZero && hasVisible); y++ {
+		for x := bounds.Min.X; x < bounds.Max.X; x++ {
+			_, _, _, a := source.At(x, y).RGBA()
+			if a == 0 {
+				hasZero = true
+			} else {
+				hasVisible = true
+			}
+			if hasZero && hasVisible {
+				break
+			}
+		}
+	}
+	if !hasZero || !hasVisible {
+		return original, 0
+	}
+	return &transparentEdgeImage64{source: source, rect: image.Rect(0, 0, bounds.Dx()+2, bounds.Dy()+2)}, 1
+}
+
+// transparentEdgeImage64 按需补齐十六位像素边缘，保留原始只读图像
+type transparentEdgeImage64 struct {
+	source image.Image
+	rect   image.Rectangle
+}
+
+// Bounds 返回含采样边距的图像边界
+// 返回: image.Rectangle 图像边界
+func (s *transparentEdgeImage64) Bounds() image.Rectangle { return s.rect }
+
+// ColorModel 返回十六位非预乘颜色模型
+// 返回: color.Model 颜色模型
+func (s *transparentEdgeImage64) ColorModel() color.Model { return color.NRGBA64Model }
+
+// At 读取十六位原始颜色，透明邻域使用最小非零透明度保留边缘颜色
+// 入参: x 横向坐标, y 纵向坐标
+// 返回: color.Color 非预乘颜色
+func (s *transparentEdgeImage64) At(x, y int) color.Color {
+	if !image.Pt(x, y).In(s.rect) {
+		return color.NRGBA64{}
+	}
+	b := s.source.Bounds()
+	sx, sy := b.Min.X+min(max(x-1, 0), b.Dx()-1), b.Min.Y+min(max(y-1, 0), b.Dy()-1)
+	c := color.NRGBA64Model.Convert(s.source.At(sx, sy)).(color.NRGBA64)
+	if c.A == 0 {
+		var best color.NRGBA64
+		for ny := max(sy-1, b.Min.Y); ny < min(sy+2, b.Max.Y); ny++ {
+			for nx := max(sx-1, b.Min.X); nx < min(sx+2, b.Max.X); nx++ {
+				v := color.NRGBA64Model.Convert(s.source.At(nx, ny)).(color.NRGBA64)
+				if v.A > best.A {
+					best = v
+				}
+			}
+		}
+		if best.A != 0 {
+			best.A = 1
+			c = best
+		}
+	}
+	if x == 0 || y == 0 || x == s.rect.Max.X-1 || y == s.rect.Max.Y-1 {
+		c.A = 1
+	}
+	return c
+}
+
+// RGBA64At 返回保留原采样精度的预乘颜色
+// 入参: x 横向坐标, y 纵向坐标
+// 返回: color.RGBA64 预乘颜色
+func (s *transparentEdgeImage64) RGBA64At(x, y int) color.RGBA64 {
+	r, g, b, a := s.At(x, y).RGBA()
+	return color.RGBA64{R: uint16(r), G: uint16(g), B: uint16(b), A: uint16(a)}
+}