mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-30 01:27:26 +08:00
277 lines
9.4 KiB
Go
277 lines
9.4 KiB
Go
// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ofdgo
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import (
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"fmt"
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"image"
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"image/color"
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"image/draw"
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"slices"
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"github.com/tdewolff/canvas"
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"github.com/tdewolff/canvas/renderers/rasterizer"
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)
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// CanvasBackend canvas页面编译与绘制适配器，ColorSpace仅影响光栅输出
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type CanvasBackend struct {
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ColorSpace canvas.ColorSpace
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}
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// rasterStrokeGradientCanvas 保留页面坐标描边的局部渐变定位
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type rasterStrokeGradientCanvas struct {
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rasterGradientCanvas
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inverse RasterMatrix
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}
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// rasterGradientCanvas 将公共渐变交给Canvas采样，不改变OFD周期语义
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type rasterGradientCanvas struct {
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gradient *RasterGradient
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space canvas.ColorSpace
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}
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// Name 返回后端标识
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// 返回: string 后端标识
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func (CanvasBackend) Name() string { return "canvas" }
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// Render 绘制已编译页面，不修改输入数据
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// 入参: page 只读页面
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// 返回: image.Image 图像, error 绘制错误
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func (b CanvasBackend) Render(page *RasterPage) (image.Image, error) {
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w, h, err := page.PixelSize()
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if err != nil {
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return nil, err
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}
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img := image.NewRGBA(image.Rect(0, 0, w, h))
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return b.renderImage(page, img)
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}
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// RenderInto 在调用方独占的紧密RGBA缓冲中重新绘制，不修改页面或保留缓冲
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// 入参: page 只读页面, target 原点为零且尺寸匹配的目标，不与输入图像共享数据
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// 返回: error 参数或绘制错误，绘制失败时目标可能包含部分结果
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func (b CanvasBackend) RenderInto(page *RasterPage, target *image.RGBA) error {
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w, h, err := page.PixelSize()
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if err != nil {
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return err
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}
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if target == nil || target.Rect != image.Rect(0, 0, w, h) || target.Stride != 4*w || len(target.Pix) < 4*w*h {
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return fmt.Errorf("invalid canvas target buffer")
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}
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clear(target.Pix[:4*w*h])
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_, err = b.renderImage(page, target)
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return err
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}
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// renderImage 将页面绘制到已清空且尺寸匹配的目标
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// 入参: page 只读页面, img 独占目标
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// 返回: image.Image 目标图像, error 绘制错误
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func (b CanvasBackend) renderImage(page *RasterPage, img *image.RGBA) (image.Image, error) {
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h := img.Rect.Dy()
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space := b.ColorSpace
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if space == nil {
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space = canvas.DefaultColorSpace
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}
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r := rasterizer.FromImage(img, canvas.DPMM(page.DPI/25.4), space)
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masks := renderCache[[32]byte, *image.Alpha]{limit: 16 << 20}
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for i, cmd := range page.Commands {
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if cmd.Image != nil {
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source, err := imagePixelData(cmd.Image)
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if err != nil {
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return nil, fmt.Errorf("canvas image %d: %w", i, err)
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}
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if _, linear := space.(canvas.LinearColorSpace); !linear {
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converted := image.NewRGBA(source.Bounds())
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for y := source.Bounds().Min.Y; y < source.Bounds().Max.Y; y++ {
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for x := source.Bounds().Min.X; x < source.Bounds().Max.X; x++ {
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converted.SetRGBA(x, y, space.ToLinear(color.RGBAModel.Convert(source.At(x, y)).(color.RGBA)))
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}
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}
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source = converted
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}
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if err := drawRasterImageCommand(b, page, img, source, cmd, &masks); err != nil {
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return nil, err
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}
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continue
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}
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p := &canvas.Path{}
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for _, s := range cmd.Path {
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switch s.Verb {
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case RasterMove:
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p.MoveTo(s.End.X, s.End.Y)
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case RasterLine:
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p.LineTo(s.End.X, s.End.Y)
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case RasterQuad:
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p.QuadTo(s.Control1.X, s.Control1.Y, s.End.X, s.End.Y)
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case RasterCubic:
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p.CubeTo(s.Control1.X, s.Control1.Y, s.Control2.X, s.Control2.Y, s.End.X, s.End.Y)
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case RasterClose:
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p.Close()
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default:
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return nil, fmt.Errorf("canvas command %d: unsupported path verb %d", i, s.Verb)
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}
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}
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paint := canvas.Paint{Color: cmd.Paint.Color}
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if g := cmd.Paint.Gradient; g != nil {
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stops := make(canvas.Grad, len(g.Stops))
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for j, stop := range g.Stops {
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stops[j] = canvas.Stop{Offset: stop.Offset, Color: stop.Color}
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}
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start, end := canvas.Point{X: g.Start.X, Y: g.Start.Y}, canvas.Point{X: g.End.X, Y: g.End.Y}
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switch g.Kind {
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case RasterLinear:
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paint = canvas.Paint{Gradient: stops.ToLinear(start, end)}
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case RasterRadial:
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paint = canvas.Paint{Gradient: stops.ToRadial(start, g.R0, end, g.R1)}
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case RasterMesh:
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paint = canvas.Paint{Gradient: rasterGradientCanvas{gradient: g}}
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default:
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return nil, fmt.Errorf("canvas command %d: unsupported gradient %d", i, g.Kind)
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}
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if g.Spread != nil || g.Sample != nil {
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paint = canvas.Paint{Gradient: rasterGradientCanvas{gradient: g}}
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}
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}
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style := canvas.Style{Fill: paint, FillRule: canvas.NonZero}
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if cmd.EvenOdd {
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style.FillRule = canvas.EvenOdd
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}
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m := cmd.Transform
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if cmd.Stroke != nil {
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options := *cmd.Stroke
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if err := validateStroke(options); err != nil {
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return nil, err
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}
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p = p.Transform(canvas.Matrix{{m[0], m[2], m[4]}, {m[1], m[3], m[5]}})
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if cmd.Paint.Gradient != nil {
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inverse, err := m.Inverse()
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if err != nil {
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return nil, err
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}
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paint = canvas.Paint{Gradient: rasterStrokeGradientCanvas{rasterGradientCanvas{gradient: cmd.Paint.Gradient}, inverse}}
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}
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line := pathStyle{lineJoin: canvas.MiterJoin, miterLimit: defaultMiterLimit}
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line.applyLineJoin(options.Join, options.MiterLimit)
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style = canvas.Style{Stroke: paint, StrokeWidth: options.Width, StrokeCapper: pathLineCap(options.Cap, canvas.ButtCap), StrokeJoiner: line.lineJoin, FillRule: canvas.NonZero}
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if len(options.Dashes) > 0 {
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style.DashOffset = options.DashOffset / options.Width
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style.Dashes = make([]float64, len(options.Dashes))
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for i, dash := range options.Dashes {
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style.Dashes[i] = dash / options.Width
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}
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}
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if slices.Contains(options.Dashes, 0) {
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var err error
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p, err = canvasStrokePath(b, p, options)
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if err != nil {
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return nil, err
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}
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style = canvas.Style{Fill: paint, FillRule: canvas.NonZero}
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}
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m = RasterMatrix{1, 0, 0, 1, 0, 0}
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}
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matrix := canvas.Matrix{{m[0], m[2], m[4]}, {-m[1], -m[3], page.Height - m[5]}}
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if cmd.Clip == nil {
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r.RenderPath(p, style, matrix)
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continue
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}
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mask, err := rasterClipMask(b, page, cmd.Clip, &masks)
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if err != nil {
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return nil, err
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}
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if mask.Rect.Empty() {
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continue
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}
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part := image.NewRGBA(image.Rect(0, 0, mask.Rect.Dx(), mask.Rect.Dy()))
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local := rasterizer.FromImage(part, canvas.DPMM(page.DPI/25.4), space)
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matrix[0][2] -= float64(mask.Rect.Min.X) / (page.DPI / 25.4)
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matrix[1][2] -= float64(h-mask.Rect.Max.Y) / (page.DPI / 25.4)
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local.RenderPath(p, style, matrix)
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draw.DrawMask(img, mask.Rect, part, image.Point{}, mask, mask.Rect.Min, draw.Over)
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}
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r.Close()
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return img, nil
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}
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// At 返回原局部坐标的描边渐变颜色
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// 入参: x 页面横坐标, y 页面纵坐标
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// 返回: color.RGBA 预乘颜色
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func (g rasterStrokeGradientCanvas) At(x, y float64) color.RGBA {
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p := g.inverse.Apply(RasterPoint{x, y})
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return g.rasterGradientCanvas.At(p.X, p.Y)
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}
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// SetColorSpace 转换描边渐变颜色，不修改共享分段
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// 入参: space 颜色空间
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// 返回: canvas.Gradient 独立渐变
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func (g rasterStrokeGradientCanvas) SetColorSpace(space canvas.ColorSpace) canvas.Gradient {
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g.rasterGradientCanvas = g.rasterGradientCanvas.SetColorSpace(space).(rasterGradientCanvas)
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return g
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}
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// At 返回局部坐标的预乘颜色
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// 入参: x 横坐标, y 纵坐标
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// 返回: color.RGBA 渐变颜色
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func (g rasterGradientCanvas) At(x, y float64) color.RGBA {
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value := g.gradient.At(x, y)
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if g.space != nil {
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return g.space.ToLinear(value)
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}
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return value
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}
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// SetColorSpace 返回转换颜色空间后的独立渐变
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// 入参: space 目标颜色空间
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// 返回: canvas.Gradient 采样器
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func (g rasterGradientCanvas) SetColorSpace(space canvas.ColorSpace) canvas.Gradient {
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if g.gradient.Mesh != nil || g.gradient.Sample != nil {
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g.space = space
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return g
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}
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copy := *g.gradient
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copy.Stops = append([]ColorStop(nil), copy.Stops...)
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for i := range copy.Stops {
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copy.Stops[i].Color = space.ToLinear(copy.Stops[i].Color)
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}
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return rasterGradientCanvas{gradient: ©}
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}
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// init 注册Canvas适配器和默认组合
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func init() {
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if err := RegisterRenderBackend("canvas", defaultRenderBackends); err != nil {
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panic(err)
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}
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}
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// defaultRenderBackends 创建默认组合，调用方可按职责替换任意后端
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// 返回: RenderBackends 默认后端组合
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func defaultRenderBackends() RenderBackends {
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backend := CanvasBackend{}
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return RenderBackends{FontResources: SFNTBackend{}, Fonts: SFNTBackend{}, Geometry: backend, Compiler: backend, Raster: backend, SVG: backend, PDF: backend, EPS: backend}
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}
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// OpenFont 使用独立字体后端读取字体度量
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// 入参: data 字体数据
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// 返回: FontMetrics 字体度量, error 解析错误
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func (CanvasBackend) OpenFont(data []byte) (FontMetrics, error) {
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return (SFNTBackend{}).OpenFont(data)
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}
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// ResolveFont 使用独立字体后端解析字体来源
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// 入参: r 渲染器, id 字体标识, exact 是否禁止无关回退
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// 返回: ResolvedFont 字体与来源, error 解析错误
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func (CanvasBackend) ResolveFont(r *Renderer, id string, exact bool) (ResolvedFont, error) {
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return (SFNTBackend{}).ResolveFont(r, id, exact)
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}
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