feat(渲染能力): 完善径向渐变延伸与镜像渐变渲染，保持全矢量输出

ofdgo_page.go

@@ -184,6 +184,8 @@ type StrokeColor struct {
 
 // AxialShd 轴向渐变
 type AxialShd struct {
+	MapType    string       `xml:"MapType,attr"`
+	MapUnit    float64      `xml:"MapUnit,attr"`
 	Extend     string       `xml:"Extend,attr"`
 	StartPoint string       `xml:"StartPoint,attr"`
 	EndPoint   string       `xml:"EndPoint,attr"`
@@ -192,6 +194,8 @@ type AxialShd struct {
 
 // RadialShd 径向渐变
 type RadialShd struct {
+	MapType     string       `xml:"MapType,attr"`
+	MapUnit     float64      `xml:"MapUnit,attr"`
 	Extend      string       `xml:"Extend,attr"`
 	StartPoint  string       `xml:"StartPoint,attr"`
 	StartRadius float64      `xml:"StartRadius,attr"`

ofdgo_paint.go

@@ -165,10 +165,10 @@ func parseFillPaint(fillColor *FillColor, x, y, pageH float64) any {
 		return nil
 	}
 	if gradient := parseAxialShdGradient(fillColor.AxialShd, fillColor.Alpha, x, y, pageH); gradient != nil {
-		return gradient
+		return newShdPaint(gradient, fillColor.AxialShd.Extend, fillColor.AxialShd.MapType, fillColor.AxialShd.MapUnit)
 	}
 	if gradient := parseRadialShdGradient(fillColor.RadialShd, fillColor.Alpha, x, y, pageH); gradient != nil {
-		return gradient
+		return newShdPaint(gradient, fillColor.RadialShd.Extend, fillColor.RadialShd.MapType, fillColor.RadialShd.MapUnit)
 	}
 	if fillColor.AxialShd != nil {
 		return parseShdColor(fillColor.AxialShd.Segment, fillColor.Alpha)
@@ -209,10 +209,10 @@ func parseStrokePaint(strokeColor *StrokeColor, x, y, pageH float64) any {
 		return nil
 	}
 	if gradient := parseAxialShdGradient(strokeColor.AxialShd, strokeColor.Alpha, x, y, pageH); gradient != nil {
-		return gradient
+		return newShdPaint(gradient, strokeColor.AxialShd.Extend, strokeColor.AxialShd.MapType, strokeColor.AxialShd.MapUnit)
 	}
 	if gradient := parseRadialShdGradient(strokeColor.RadialShd, strokeColor.Alpha, x, y, pageH); gradient != nil {
-		return gradient
+		return newShdPaint(gradient, strokeColor.RadialShd.Extend, strokeColor.RadialShd.MapType, strokeColor.RadialShd.MapUnit)
 	}
 	if strokeColor.AxialShd != nil {
 		return parseShdColor(strokeColor.AxialShd.Segment, strokeColor.Alpha)
@@ -312,14 +312,9 @@ func parseAxialShdGradient(axialShd *AxialShd, alpha *int, x, y, pageH float64)
 }
 
 // axialShdClip 获取轴向渐变的延伸裁剪区域
-// 入参: ctx 画布上下文, paint 画刷, shading 轴向渐变节点
+// 入参: ctx 画布上下文, gradient 轴向渐变, extend 延伸方向
 // 返回: *canvas.Path 裁剪区域
-func axialShdClip(ctx *canvas.Context, paint any, shading *AxialShd) *canvas.Path {
-	gradient, ok := paint.(*canvas.LinearGradient)
-	if !ok || shading == nil {
-		return nil
-	}
-	extend, _ := strconv.Atoi(shading.Extend)
+func axialShdClip(ctx *canvas.Context, gradient *canvas.LinearGradient, extend int) *canvas.Path {
 	if extend == 3 {
 		return nil
 	}

ofdgo_renderer_path.go

@@ -30,8 +30,6 @@ type pathStyle struct {
 	strokeColor      color.Color
 	fillPaint        any
 	strokePaint      any
-	fillAxialShd     *AxialShd
-	strokeAxialShd   *AxialShd
 	fillPattern      *Pattern
 	fillPatternColor color.Color
 	lineWidth        float64
@@ -68,7 +66,6 @@ func (s *pathStyle) applyFillColor(fill *FillColor, bx, by, pageH float64, alpha
 	s.fillPatternColor = patternColor(fillColorNode)
 	s.fillColor = parseFillColor(fillColorNode)
 	s.fillPaint = parseFillPaint(fillColorNode, bx, by, pageH)
-	s.fillAxialShd = fillColorNode.AxialShd
 }
 
 // applyStrokeColor 应用描边颜色
@@ -77,7 +74,6 @@ func (s *pathStyle) applyStrokeColor(stroke *StrokeColor, bx, by, pageH float64,
 	strokeColorNode := withStrokeAlpha(stroke, alpha)
 	s.strokeColor = parseStrokeColor(strokeColorNode)
 	s.strokePaint = parseStrokePaint(strokeColorNode, bx, by, pageH)
-	s.strokeAxialShd = strokeColorNode.AxialShd
 }
 
 // pathLineCap 转换线帽样式
@@ -215,7 +211,8 @@ func (r *Renderer) renderPath(ctx *canvas.Context, obj PathObject, pageH float64
 		style.fillPaint = style.fillColor
 	}
 	if shouldFill {
-		fillClip := intersectClipPath(clipPath, axialShdClip(ctx, style.fillPaint, style.fillAxialShd))
+		fillPaint, shadingClip := resolveShdPaint(ctx, style.fillPaint)
+		fillClip := intersectClipPath(clipPath, shadingClip)
 		fp := p
 		fillRule := canvas.NonZero
 		if obj.Rule == "Even-Odd" {
@@ -233,7 +230,7 @@ func (r *Renderer) renderPath(ctx *canvas.Context, obj PathObject, pageH float64
 			r.renderPattern(ctx, style.fillPattern, style.fillPatternColor, pageH, fp, ctm, bx, by)
 		} else if style.fillPaint != nil {
 			ctx.SetFillRule(fillRule)
-			ctx.SetFill(style.fillPaint)
+			ctx.SetFill(fillPaint)
 			ctx.SetStrokeColor(canvas.Transparent)
 			ctx.DrawPath(0, 0, fp)
 		}
@@ -250,15 +247,16 @@ func (r *Renderer) renderPath(ctx *canvas.Context, obj PathObject, pageH float64
 		if style.strokePaint == nil {
 			style.strokePaint = colorWithAlpha(canvas.Black, obj.Alpha)
 		}
+		strokePaint, shadingClip := resolveShdPaint(ctx, style.strokePaint)
 		ctx.SetFillColor(canvas.Transparent)
-		ctx.SetStroke(style.strokePaint)
+		ctx.SetStroke(strokePaint)
 		ctx.SetStrokeWidth(style.lineWidth)
 		ctx.SetStrokeCapper(style.lineCap)
 		ctx.SetStrokeJoiner(style.lineJoin)
 		if len(style.dashPattern) > 0 {
 			ctx.SetDashes(style.dashOffset, style.dashPattern...)
 		}
-		strokeClip := intersectClipPath(clipPath, axialShdClip(ctx, style.strokePaint, style.strokeAxialShd))
+		strokeClip := intersectClipPath(clipPath, shadingClip)
 		if strokeClip != nil {
 			sp := p.Copy()
 			if len(style.dashPattern) > 0 {
@@ -266,7 +264,7 @@ func (r *Renderer) renderPath(ctx *canvas.Context, obj PathObject, pageH float64
 			}
 			sp = sp.Stroke(style.lineWidth, style.lineCap, style.lineJoin, canvas.Tolerance)
 			sp = applyClipPath(sp, strokeClip)
-			ctx.SetFill(style.strokePaint)
+			ctx.SetFill(strokePaint)
 			ctx.SetStrokeColor(canvas.Transparent)
 			ctx.DrawPath(0, 0, sp)
 		} else {

ofdgo_renderer_text.go

@@ -76,24 +76,21 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 		fillColor = colorWithAlpha(canvas.Black, obj.Alpha)
 	}
 	var fillPaint any = fillColor
-	var fillColorNode *FillColor
 	if dp != nil && dp.FillColor != nil {
-		fillColorNode = withFillAlpha(dp.FillColor, obj.Alpha)
+		fillColorNode := withFillAlpha(dp.FillColor, obj.Alpha)
 		fillColor = parseFillColor(fillColorNode)
 		fillPaint = parseFillPaint(fillColorNode, bx, by, pageH)
 	}
 	if obj.FillColor != nil {
-		fillColorNode = withFillAlpha(obj.FillColor, obj.Alpha)
+		fillColorNode := withFillAlpha(obj.FillColor, obj.Alpha)
 		fillColor = parseFillColor(fillColorNode)
 		fillPaint = parseFillPaint(fillColorNode, bx, by, pageH)
 	}
 	if fillPaint == nil {
 		fillPaint = fillColor
 	}
-	fillClip := clipPath
-	if fillColorNode != nil {
-		fillClip = intersectClipPath(fillClip, axialShdClip(ctx, fillPaint, fillColorNode.AxialShd))
-	}
+	fillPaint, shadingClip := resolveShdPaint(ctx, fillPaint)
+	fillClip := intersectClipPath(clipPath, shadingClip)
 	strokeStyle := newPathStyle(nil, defaultStroke, 0, obj.Alpha)
 	strokeClip := clipPath
 	if shouldStroke {
@@ -110,7 +107,8 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 			strokeStyle.strokePaint = colorWithAlpha(canvas.Black, obj.Alpha)
 		}
 		strokeStyle.scale(ctm)
-		strokeClip = intersectClipPath(strokeClip, axialShdClip(ctx, strokeStyle.strokePaint, strokeStyle.strokeAxialShd))
+		strokeStyle.strokePaint, shadingClip = resolveShdPaint(ctx, strokeStyle.strokePaint)
+		strokeClip = intersectClipPath(strokeClip, shadingClip)
 	}
 	fontStyle := canvas.FontRegular
 	weight := obj.Weight
@@ -150,7 +148,7 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 	face := ff.Face(sizePt, fillPaint, fontStyle, canvas.FontNormal)
 	glyphTransforms := r.textObjectGlyphTransforms(fontID, obj)
 	hasUnderline := strings.Contains(obj.Decoration, "Underline")
-	_, axialFill := fillPaint.(*canvas.LinearGradient)
+	_, shadedFill := fillPaint.(canvas.Gradient)
 	verticalAdvance := (obj.ReadDirection-obj.CharDirection)%180 != 0
 	advanceX, advanceY := 1.0, 0.0
 	switch obj.ReadDirection {
@@ -174,7 +172,7 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 		}
 		dxs, dys := parseFloats(tc.DeltaX), parseFloats(tc.DeltaY)
 		xs, ys := parseFloats(tc.X), parseFloats(tc.Y)
-		drawAsPath := embeddedFont || textCodePositioned(tc, xs, ys) || fillClip != nil || axialFill || shouldStroke
+		drawAsPath := embeddedFont || textCodePositioned(tc, xs, ys) || fillClip != nil || shadedFill || shouldStroke
 		cx, cy := 0.0, 0.0
 		previousAdvance := 0.0
 		if len(xs) > 0 {
@@ -265,7 +263,7 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 			}
 			if fillPaint != nil {
 				ctx.SetFill(fillPaint)
-				if fillClip != nil || axialFill {
+				if fillClip != nil || shadedFill {
 					scaleX := hScale
 					if advanceLimit > 0 && glyphWidth*scaleX > advanceLimit {
 						scaleX = advanceLimit / glyphWidth

ofdgo_shading.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 (
+	"math"
+	"strconv"
+
+	"github.com/tdewolff/canvas"
+)
+
+type shdPaint struct {
+	gradient canvas.Gradient
+	extend   int
+	mapType  string
+	period   float64
+}
+
+// newShdPaint 创建渐变画刷
+// 入参: gradient 渐变对象, extend 延伸方向, mapType 绘制方式, mapUnit 渐变区间长度
+// 返回: *shdPaint 渐变画刷
+func newShdPaint(gradient canvas.Gradient, extend, mapType string, mapUnit float64) *shdPaint {
+	flags, _ := strconv.Atoi(extend)
+	length := 0.0
+	switch g := gradient.(type) {
+	case *canvas.LinearGradient:
+		length = g.End.Sub(g.Start).Length()
+	case *canvas.RadialGradient:
+		length = g.C1.Sub(g.C0).Length()
+	}
+	period := 1.0
+	if mapUnit > 0 && length > 0 {
+		period = mapUnit / length
+	}
+	return &shdPaint{gradient: gradient, extend: flags, mapType: mapType, period: period}
+}
+
+// resolveShdPaint 解析渐变画刷和裁剪区域
+// 入参: ctx 画布上下文, paint 画刷
+// 返回: any 画刷, *canvas.Path 裁剪区域
+func resolveShdPaint(ctx *canvas.Context, paint any) (any, *canvas.Path) {
+	s, ok := paint.(*shdPaint)
+	if !ok {
+		return paint, nil
+	}
+	switch g := s.gradient.(type) {
+	case *canvas.LinearGradient:
+		clip := axialShdClip(ctx, g, s.extend)
+		if s.mapType != "Reflect" {
+			return g, clip
+		}
+		d := g.End.Sub(g.Start)
+		axis := canvas.Matrix{{d.X, -d.Y, g.Start.X}, {d.Y, d.X, g.Start.Y}}
+		area := shdCanvasBounds(ctx).Transform(axis.Inv())
+		lo, hi := s.rangeLimits(area.X0, area.X1)
+		if hi <= lo {
+			return g, &canvas.Path{}
+		}
+		gradient := reflectShdGrad(g.Grad, s.period, lo, hi)
+		return gradient.ToLinear(g.Start.Add(d.Mul(lo)), g.Start.Add(d.Mul(hi))), clip
+	case *canvas.RadialGradient:
+		d, dr := g.C1.Sub(g.C0), g.R1-g.R0
+		length := d.Length()
+		if length >= math.Abs(dr) {
+			return g, nil
+		}
+		clip := radialShdClip(ctx, g, s.extend)
+		if s.mapType != "Reflect" {
+			return g, clip
+		}
+		lo, hi := 0.0, 1.0
+		if s.extend != 0 {
+			distance := 0.0
+			bounds := shdCanvasBounds(ctx)
+			for _, point := range []canvas.Point{{X: bounds.X0, Y: bounds.Y0}, {X: bounds.X1, Y: bounds.Y0}, {X: bounds.X1, Y: bounds.Y1}, {X: bounds.X0, Y: bounds.Y1}} {
+				distance = math.Max(distance, point.Sub(g.C0).Length())
+			}
+			limit := (distance + g.R0) / (math.Abs(dr) - length)
+			lo, hi = s.rangeLimits(-limit, limit)
+		}
+		if dr > 0 {
+			lo = math.Max(lo, -g.R0/dr)
+		} else {
+			hi = math.Min(hi, -g.R0/dr)
+		}
+		if hi <= lo {
+			return g, &canvas.Path{}
+		}
+		gradient := reflectShdGrad(g.Grad, s.period, lo, hi)
+		return gradient.ToRadial(g.C0.Add(d.Mul(lo)), math.Max(0, g.R0+dr*lo), g.C0.Add(d.Mul(hi)), math.Max(0, g.R0+dr*hi)), clip
+	}
+	return s.gradient, nil
+}
+
+// rangeLimits 限制渐变延伸区间
+// 入参: lo 区间起点, hi 区间终点
+// 返回: float64 起点, float64 终点
+func (s *shdPaint) rangeLimits(lo, hi float64) (float64, float64) {
+	if s.extend&1 == 0 {
+		lo = math.Max(lo, 0)
+	}
+	if s.extend&2 == 0 {
+		hi = math.Min(hi, 1)
+	}
+	return lo, hi
+}
+
+// shdCanvasBounds 获取渐变坐标系下的画布边界
+// 入参: ctx 画布上下文
+// 返回: canvas.Rect 画布边界
+func shdCanvasBounds(ctx *canvas.Context) canvas.Rect {
+	origin := ctx.CoordView().Dot(canvas.Point{})
+	view := ctx.CoordSystemView().Mul(ctx.View()).Translate(origin.X, origin.Y)
+	if view.Det() == 0 {
+		return canvas.Rect{}
+	}
+	width, height := ctx.Size()
+	return (canvas.Rect{X1: width, Y1: height}).Transform(view.Inv())
+}
+
+// radialShdClip 获取包含双圆的径向渐变裁剪区域
+// 入参: ctx 画布上下文, g 径向渐变, extend 延伸方向
+// 返回: *canvas.Path 裁剪区域
+func radialShdClip(ctx *canvas.Context, g *canvas.RadialGradient, extend int) *canvas.Path {
+	inner, outer := g.C0, g.C1
+	r0, r1 := g.R0, g.R1
+	if r1 < r0 {
+		inner, outer, r0, r1 = outer, inner, r1, r0
+		extend = (extend&1)<<1 | (extend&2)>>1
+	}
+	if extend == 3 {
+		return nil
+	}
+	var clip *canvas.Path
+	if extend&2 == 0 {
+		clip = canvas.Circle(r1).Translate(outer.X, outer.Y)
+	} else {
+		clip = shdCanvasBounds(ctx).ToPath()
+	}
+	if extend&1 == 0 && r0 > 0 {
+		clip = clip.Not(canvas.Circle(r0).Translate(inner.X, inner.Y))
+	}
+	return clip
+}
+
+// reflectShdGrad 构造镜像渐变颜色分段
+// 入参: gradient 颜色分段, period 周期长度, lo 起点, hi 终点
+// 返回: canvas.Grad 镜像颜色分段
+func reflectShdGrad(gradient canvas.Grad, period, lo, hi float64) canvas.Grad {
+	base := append(canvas.Grad{{Offset: 0, Color: gradient.At(0)}}, gradient...)
+	base = append(base, canvas.Stop{Offset: 1, Color: gradient.At(1)})
+	reversed := make(canvas.Grad, len(base))
+	for i, stop := range base {
+		reversed[len(base)-1-i] = canvas.Stop{Offset: 1 - stop.Offset, Color: stop.Color}
+	}
+	result := canvas.Grad{{Offset: 0, Color: gradient.At(reflectShdPosition(lo / period))}}
+	for i, last := math.Floor(lo/period), math.Ceil(hi/period); i < last; i++ {
+		stops := base
+		if math.Mod(i, 2) != 0 {
+			stops = reversed
+		}
+		for _, stop := range stops {
+			position := (i + stop.Offset) * period
+			offset := (position - lo) / (hi - lo)
+			if lo < position && position < hi && result[len(result)-1].Offset < offset {
+				result = append(result, canvas.Stop{Offset: offset, Color: stop.Color})
+			}
+		}
+	}
+	return append(result, canvas.Stop{Offset: 1, Color: gradient.At(reflectShdPosition(hi / period))})
+}
+
+// reflectShdPosition 获取镜像周期内的位置
+// 入参: position 渐变位置
+// 返回: float64 周期内的位置
+func reflectShdPosition(position float64) float64 {
+	index := math.Floor(position)
+	position -= index
+	if math.Mod(index, 2) != 0 {
+		return 1 - position
+	}
+	return position
+}