feat(渲染编辑): 修复保存、文字与渲染问题

ofdgo_renderer_gradient_gg.go

@@ -0,0 +1,116 @@
+// 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 (
+	"fmt"
+	"image/color"
+	"math"
+
+	"github.com/gogpu/gg"
+)
+
+// ggGradientBrush 仅在颜色插值及延伸等价时使用原生渐变，否则保留OFD采样
+// 入参: gradient 局部渐变, matrix 局部到像素变换
+// 返回: gg.Brush 画刷, error 类型或变换错误
+func ggGradientBrush(gradient *RasterGradient, matrix RasterMatrix) (gg.Brush, error) {
+	if gradient.Kind != RasterLinear && gradient.Kind != RasterRadial {
+		return nil, fmt.Errorf("unsupported gradient %d", gradient.Kind)
+	}
+	inverse, err := matrix.Inverse()
+	if err != nil {
+		return nil, err
+	}
+	if brush := ggNativeGradient(gradient, matrix, inverse); brush != nil {
+		return brush, nil
+	}
+	return gg.NewCustomBrush(func(x, y float64) gg.RGBA {
+		p := inverse.Apply(RasterPoint{X: x, Y: y})
+		return ggRGBA(gradient.At(p.X, p.Y))
+	}), nil
+}
+
+// ggNativeGradient 将恒定非预乘色的透明度渐变映射为GG原生画刷
+// GG使用线性光颜色插值，不接受改变色相、重复节点或单侧透明延伸的OFD渐变
+// 入参: g 局部渐变, matrix 正变换, inverse 逆变换
+// 返回: gg.Brush 等价原生画刷，不匹配时为空
+func ggNativeGradient(g *RasterGradient, matrix, inverse RasterMatrix) gg.Brush {
+	if len(g.Stops) < 2 {
+		return nil
+	}
+	var reference color.RGBA
+	for i, stop := range g.Stops {
+		if !finite(stop.Offset) || stop.Offset < 0 || stop.Offset > 1 || i > 0 && stop.Offset <= g.Stops[i-1].Offset {
+			return nil
+		}
+		if stop.Color.A > reference.A {
+			reference = stop.Color
+		}
+	}
+	if reference.A == 0 {
+		return nil
+	}
+	for _, stop := range g.Stops {
+		c := stop.Color
+		if uint32(c.R)*uint32(reference.A) != uint32(reference.R)*uint32(c.A) ||
+			uint32(c.G)*uint32(reference.A) != uint32(reference.G)*uint32(c.A) ||
+			uint32(c.B)*uint32(reference.A) != uint32(reference.B)*uint32(c.A) {
+			return nil
+		}
+	}
+	extend, period := gg.ExtendPad, 1.0
+	if spread := g.Spread; spread != nil {
+		if spread.Extend != 3 {
+			return nil
+		}
+		switch spread.MapType {
+		case "Repeat":
+			extend = gg.ExtendRepeat
+		case "Reflect":
+			extend = gg.ExtendReflect
+		}
+		if extend != gg.ExtendPad && spread.Period > 0 {
+			period = spread.Period
+		}
+	}
+	stops := make([]gg.ColorStop, len(g.Stops))
+	for i, stop := range g.Stops {
+		c := ggRGBA(reference)
+		c.A = float64(stop.Color.A) / 255
+		stops[i] = gg.ColorStop{Offset: stop.Offset, Color: c}
+	}
+	start := matrix.Apply(g.Start)
+	if g.Kind == RasterLinear {
+		dx, dy := g.End.X-g.Start.X, g.End.Y-g.Start.Y
+		length := dx*dx + dy*dy
+		if !rasterPositive(length) {
+			return nil
+		}
+		// 渐变参数为协向量，非等比缩放或错切不能直接变换两个端点
+		x, y := (inverse[0]*dx+inverse[1]*dy)/length, (inverse[2]*dx+inverse[3]*dy)/length
+		factor := period / (x*x + y*y)
+		brush := gg.NewLinearGradientBrush(start.X, start.Y, start.X+x*factor, start.Y+y*factor)
+		brush.Stops, brush.Extend = stops, extend
+		return brush
+	}
+	xscale, yscale := math.Hypot(matrix[0], matrix[1]), math.Hypot(matrix[2], matrix[3])
+	if g.Start != g.End || g.R0 != 0 || !rasterPositive(g.R1) ||
+		math.Abs(xscale-yscale) > 1e-12*xscale || math.Abs(matrix[0]*matrix[2]+matrix[1]*matrix[3]) > 1e-12*xscale*yscale {
+		return nil
+	}
+	brush := gg.NewRadialGradientBrush(start.X, start.Y, 0, g.R1*xscale*period)
+	brush.Stops, brush.Extend = stops, extend
+	return brush
+}