refactor(重构代码): 拆分代码，提升代码质量

ofdgo_renderer_image.go

@@ -0,0 +1,195 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ofdgo
+
+import (
+	"image"
+	"image/color"
+
+	"github.com/tdewolff/canvas"
+)
+
+// renderImage 渲染图片
+// 入参: ctx 画布上下文, obj 图片对象, pageH 页面高度, parentCTM 父级CTM, boundaryInCTM 边界是否参与父级CTM
+func (r *Renderer) renderImage(ctx *canvas.Context, obj ImageObject, pageH float64, parentCTM *Matrix, boundaryInCTM bool) {
+	if obj.Visible != nil && !*obj.Visible {
+		return
+	}
+	resPath, ok := r.Reader.ResMap[obj.ResourceID]
+	if !ok {
+		return
+	}
+	imgData, err := r.Reader.ResData(resPath)
+	if err != nil {
+		return
+	}
+	img, _, err := decodeImageData(imgData)
+	if err != nil {
+		return
+	}
+	box, _ := ParseBox(obj.Boundary)
+	imgBounds := img.Bounds()
+	imgW, imgH := float64(imgBounds.Dx()), float64(imgBounds.Dy())
+	if imgW <= 0 || imgH <= 0 {
+		return
+	}
+	img = imageWithAlpha(img, obj.Alpha)
+	pad := 0
+	img, pad = imageWithTransparentEdge(img)
+	ctm := NewMatrix(obj.CTM)
+	if obj.CTM == "" {
+		ctm = Matrix{a: box.W, d: box.H}
+	}
+	var m canvas.Matrix
+	if boundaryInCTM && parentCTM != nil {
+		x0 := box.X + ctm.c + ctm.e
+		y0 := box.Y + ctm.d + ctm.f
+		m = canvas.Matrix{
+			{(parentCTM.a*ctm.a + parentCTM.c*ctm.b) / imgW, -(parentCTM.a*ctm.c + parentCTM.c*ctm.d) / imgH, parentCTM.a*x0 + parentCTM.c*y0 + parentCTM.e},
+			{-(parentCTM.b*ctm.a + parentCTM.d*ctm.b) / imgW, (parentCTM.b*ctm.c + parentCTM.d*ctm.d) / imgH, pageH - (parentCTM.b*x0 + parentCTM.d*y0 + parentCTM.f)},
+		}
+	} else {
+		if parentCTM != nil {
+			ctm = parentCTM.Multiply(ctm)
+		}
+		m = canvas.Matrix{
+			{ctm.a / imgW, -ctm.c / imgH, box.X + ctm.c + ctm.e},
+			{-ctm.b / imgW, ctm.d / imgH, pageH - box.Y - ctm.d - ctm.f},
+		}
+	}
+	if pad > 0 {
+		p := float64(pad)
+		m[0][2] -= m[0][0]*p + m[0][1]*p
+		m[1][2] -= m[1][0]*p + m[1][1]*p
+	}
+	ctx.RenderImage(img, ctx.CoordSystemView().Mul(ctx.View()).Mul(m))
+}
+
+// imageWithAlpha 合并图片透明度
+// 入参: img 图片对象, alpha 对象透明度
+// 返回: image.Image 合并后的图片对象
+func imageWithAlpha(img image.Image, alpha *int) image.Image {
+	if img == nil || alpha == nil {
+		return img
+	}
+	a := clampColor(*alpha)
+	if a == 255 {
+		return img
+	}
+	bounds := img.Bounds()
+	out := image.NewNRGBA(bounds)
+	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+		for x := bounds.Min.X; x < bounds.Max.X; x++ {
+			c := color.NRGBAModel.Convert(img.At(x, y)).(color.NRGBA)
+			c.A = uint8(int(c.A) * a / 255)
+			out.SetNRGBA(x, y, c)
+		}
+	}
+	return out
+}
+
+// imageWithTransparentEdge 补齐透明图片边缘颜色
+// 入参: img 图片对象
+// 返回: image.Image 补齐后的图片对象, int 补齐像素数
+func imageWithTransparentEdge(img image.Image) (image.Image, int) {
+	if img == nil {
+		return img, 0
+	}
+	bounds := img.Bounds()
+	w, h := bounds.Dx(), bounds.Dy()
+	if w == 0 || h == 0 {
+		return img, 0
+	}
+	if opaque, ok := img.(interface{ Opaque() bool }); ok && opaque.Opaque() {
+		return img, 0
+	}
+	src := image.NewNRGBA(image.Rect(0, 0, w, h))
+	hasZero, hasVisible := false, false
+	for y := 0; y < h; y++ {
+		for x := 0; x < w; x++ {
+			c := color.NRGBAModel.Convert(img.At(bounds.Min.X+x, bounds.Min.Y+y)).(color.NRGBA)
+			src.SetNRGBA(x, y, c)
+			if c.A == 0 {
+				hasZero = true
+			} else {
+				hasVisible = true
+			}
+		}
+	}
+	if !hasZero || !hasVisible {
+		return img, 0
+	}
+	out := image.NewNRGBA(image.Rect(0, 0, w+2, h+2))
+	for y := 0; y < h; y++ {
+		for x := 0; x < w; x++ {
+			c := src.NRGBAAt(x, y)
+			if c.A == 0 {
+				if edge, ok := transparentEdgeColor(src, x, y); ok {
+					c = edge
+				}
+			}
+			out.SetNRGBA(x+1, y+1, c)
+		}
+	}
+	for x := 0; x < w; x++ {
+		out.SetNRGBA(x+1, 0, transparentPaddingColor(out.NRGBAAt(x+1, 1)))
+		out.SetNRGBA(x+1, h+1, transparentPaddingColor(out.NRGBAAt(x+1, h)))
+	}
+	for y := 0; y < h; y++ {
+		out.SetNRGBA(0, y+1, transparentPaddingColor(out.NRGBAAt(1, y+1)))
+		out.SetNRGBA(w+1, y+1, transparentPaddingColor(out.NRGBAAt(w, y+1)))
+	}
+	out.SetNRGBA(0, 0, transparentPaddingColor(out.NRGBAAt(1, 1)))
+	out.SetNRGBA(w+1, 0, transparentPaddingColor(out.NRGBAAt(w, 1)))
+	out.SetNRGBA(0, h+1, transparentPaddingColor(out.NRGBAAt(1, h)))
+	out.SetNRGBA(w+1, h+1, transparentPaddingColor(out.NRGBAAt(w, h)))
+	return out, 1
+}
+
+// transparentEdgeColor 获取透明像素相邻的可见颜色
+// 入参: img 图片对象, x X坐标, y Y坐标
+// 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
+			}
+		}
+	}
+	if best.A == 0 {
+		return color.NRGBA{}, false
+	}
+	best.A = 1
+	return best, true
+}
+
+// transparentPaddingColor 获取透明补齐颜色
+// 入参: c 边缘颜色
+// 返回: color.NRGBA 补齐颜色
+func transparentPaddingColor(c color.NRGBA) color.NRGBA {
+	c.A = 1
+	return c
+}