fix(图像性能): 优化图像采样与裁剪性能

go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/tdewolff/canvas v0.0.0-20260923214215-09804640d00c
 	github.com/tdewolff/font v0.0.0-20260913163313-54f98bb59ee6
 	github.com/xiaoqidun/jbig2 v1.1.1
-	github.com/xiaoqidun/pdfgo v0.0.0-20260927111518-3299b44c9705
+	github.com/xiaoqidun/pdfgo v0.0.0-20260927114248-f2deafc71b89
 	golang.org/x/crypto v0.57.0
 	golang.org/x/image v0.46.0
 	golang.org/x/text v0.42.0

go.sum

@@ -62,8 +62,8 @@ github.com/tdewolff/test v1.0.12 h1:7F21DqIajswxuche0geHdrUZRCWE4oko4b7bcmkkrxk=
 github.com/tdewolff/test v1.0.12/go.mod h1:XPuWBzvdUzhCuxWO1ojpXsyzsA5bFoS3tO/Q3kFuTG8=
 github.com/xiaoqidun/jbig2 v1.1.1 h1:SjliS9ZO0e9HX5oYUfBuXrfFsXhWricrSz+XY4zORDI=
 github.com/xiaoqidun/jbig2 v1.1.1/go.mod h1:8QonVWtENmh2kc6l+leqeGl7psb79DWlHDkCpdChjfQ=
-github.com/xiaoqidun/pdfgo v0.0.0-20260927111518-3299b44c9705 h1:DgUrxq3/Mn3218rwv3Daw1FHcbmR0E3aOIsa6VZMMNQ=
-github.com/xiaoqidun/pdfgo v0.0.0-20260927111518-3299b44c9705/go.mod h1:4Pf0JO0BEf1uzRY+uZjlMjN/OPn3PYa0YMi6cqPPTLQ=
+github.com/xiaoqidun/pdfgo v0.0.0-20260927114248-f2deafc71b89 h1:pdnJkITNBORnYyoqU0u9MDHpjwnALvkiBS8cdJFRTRg=
+github.com/xiaoqidun/pdfgo v0.0.0-20260927114248-f2deafc71b89/go.mod h1:4Pf0JO0BEf1uzRY+uZjlMjN/OPn3PYa0YMi6cqPPTLQ=
 github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
 github.com/xyproto/randomstring v1.0.5/go.mod h1:rgmS5DeNXLivK7YprL0pY+lTuhNQW3iGxZ18UQApw/E=
 github.com/yuin/goldmark v1.8.5 h1:r6N5afV5qj/5S4UTch8agZHJ8UxNCMwX7WjkkJam2NA=

ofdgo_image.go

@@ -330,27 +330,25 @@ func imageNRGBAAt(img image.Image, x, y int) color.NRGBA {
 // 返回: color.NRGBA 颜色, bool 是否存在
 func transparentEdgeColor(img *image.NRGBA, x, y int) (color.NRGBA, bool) {
 	bounds := img.Bounds()
-	var best color.NRGBA
-	for dy := -1; dy <= 1; dy++ {
-		for dx := -1; dx <= 1; dx++ {
-			if dx == 0 && dy == 0 {
-				continue
-			}
-			nx, ny := x+dx, y+dy
-			if nx < bounds.Min.X || nx >= bounds.Max.X || ny < bounds.Min.Y || ny >= bounds.Max.Y {
-				continue
-			}
-			c := img.NRGBAAt(nx, ny)
-			if c.A > best.A {
-				best = c
+	best, alpha := 0, uint8(0)
+	left, right := max(x-1, bounds.Min.X), min(x+2, bounds.Max.X)
+scan:
+	for ny := max(y-1, bounds.Min.Y); ny < min(y+2, bounds.Max.Y); ny++ {
+		offset := img.PixOffset(left, ny)
+		for nx := left; nx < right; nx++ {
+			if (nx != x || ny != y) && img.Pix[offset+3] > alpha {
+				best, alpha = offset, img.Pix[offset+3]
+				if alpha == 255 {
+					break scan
+				}
 			}
+			offset += 4
 		}
 	}
-	if best.A == 0 {
+	if alpha == 0 {
 		return color.NRGBA{}, false
 	}
-	best.A = 1
-	return best, true
+	return color.NRGBA{R: img.Pix[best], G: img.Pix[best+1], B: img.Pix[best+2], A: 1}, true
 }
 
 // transparentPaddingColor 获取透明补齐颜色

ofdgo_raster_image.go

@@ -16,6 +16,7 @@ package ofdgo
 
 import (
 	"image"
+	"math"
 
 	"golang.org/x/image/draw"
 	"golang.org/x/image/math/f64"
@@ -43,13 +44,35 @@ func drawRasterImageCommand(backend RasterBackend, page *RasterPage, dst draw.Im
 	if mask.Rect.Empty() {
 		return nil
 	}
-	bounds := mask.Rect.Intersect(dst.Bounds())
+	bounds := mask.Rect.Intersect(dst.Bounds()).Intersect(rasterImageBounds(src.Bounds(), m, dst.Bounds()))
+	if bounds.Empty() {
+		return nil
+	}
 	layer := image.NewRGBA64(bounds)
 	draw.CatmullRom.Transform(layer, f64.Aff3{m[0], m[2], m[4], m[1], m[3], m[5]}, imagePixelSource(src), src.Bounds(), draw.Src, nil)
 	draw.DrawMask(dst, bounds, layer, bounds.Min, mask, bounds.Min, draw.Over)
 	return nil
 }
 
+// rasterImageBounds 计算采样器可能写入的像素范围，并在整数转换前裁至目标边界
+// 入参: source 原始像素边界, m 像素变换, target 目标边界
+// 返回: image.Rectangle 受影响的目标像素区域
+func rasterImageBounds(source image.Rectangle, m RasterMatrix, target image.Rectangle) image.Rectangle {
+	minX, minY, maxX, maxY := math.Inf(1), math.Inf(1), math.Inf(-1), math.Inf(-1)
+	for _, p := range [4]image.Point{source.Min, {X: source.Max.X, Y: source.Min.Y}, {X: source.Min.X, Y: source.Max.Y}, source.Max} {
+		x := math.Floor(float64(m[0]*float64(p.X)) + float64(m[2]*float64(p.Y)) + m[4])
+		y := math.Floor(float64(m[1]*float64(p.X)) + float64(m[3]*float64(p.Y)) + m[5])
+		minX, minY = math.Min(minX, x), math.Min(minY, y)
+		maxX, maxY = math.Max(maxX, x+1), math.Max(maxY, y+1)
+	}
+	minX, minY = math.Max(minX, float64(target.Min.X)), math.Max(minY, float64(target.Min.Y))
+	maxX, maxY = math.Min(maxX, float64(target.Max.X)), math.Min(maxY, float64(target.Max.Y))
+	if minX >= maxX || minY >= maxY {
+		return image.Rectangle{}
+	}
+	return image.Rect(int(minX), int(minY), int(maxX), int(maxY))
+}
+
 // PixelTransform 将页面毫米变换转换为像素变换，保留尺寸取整后的原点位置
 // 入参: m 局部到页面变换, height 目标像素高度
 // 返回: RasterMatrix 局部到像素变换