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// 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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"github.com/tdewolff/canvas"
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)
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// canvasGeometryPath 将页面坐标路径转换为默认几何引擎的向上纵轴
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// 入参: path 独立几何路径，nil表示不裁剪
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// 返回: *canvas.Path 默认引擎路径, error 不支持的路径指令
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func canvasGeometryPath(path *GeometryPath) (*canvas.Path, error) {
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if path == nil {
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return nil, nil
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}
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p := &canvas.Path{}
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for _, segment := range *path {
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switch segment.Verb {
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case GeometryMove:
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p.MoveTo(segment.End.X, -segment.End.Y)
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case GeometryLine:
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p.LineTo(segment.End.X, -segment.End.Y)
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case GeometryQuad:
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p.QuadTo(segment.Control1.X, -segment.Control1.Y, segment.End.X, -segment.End.Y)
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case GeometryCubic:
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p.CubeTo(segment.Control1.X, -segment.Control1.Y, segment.Control2.X, -segment.Control2.Y, segment.End.X, -segment.End.Y)
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case GeometryArc:
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p.ArcTo(segment.RadiusX, segment.RadiusY, -segment.Rotation, segment.Large, !segment.Sweep, segment.End.X, -segment.End.Y)
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case GeometryClose:
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p.Close()
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default:
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return nil, fmt.Errorf("unsupported geometry command %d", segment.Verb)
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}
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}
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return p, nil
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}
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// geometryCanvasPath 将默认引擎路径转换为独立的页面坐标路径，保留曲线和椭圆弧
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// 入参: path 默认引擎路径
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// 返回: *GeometryPath 独立路径，nil表示不裁剪
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func geometryCanvasPath(path *canvas.Path) *GeometryPath {
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if path == nil {
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return nil
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}
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result := make(GeometryPath, 0, path.Len())
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scanner := path.Scanner()
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for scanner.Scan() {
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end := scanner.End()
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segment := GeometrySegment{End: Point{X: end.X, Y: -end.Y}}
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switch scanner.Cmd() {
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case canvas.MoveToCmd:
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segment.Verb = GeometryMove
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case canvas.LineToCmd:
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segment.Verb = GeometryLine
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case canvas.QuadToCmd:
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control := scanner.CP1()
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segment.Verb, segment.Control1 = GeometryQuad, Point{X: control.X, Y: -control.Y}
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case canvas.CubeToCmd:
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c1, c2 := scanner.CP1(), scanner.CP2()
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segment.Verb = GeometryCubic
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segment.Control1, segment.Control2 = Point{X: c1.X, Y: -c1.Y}, Point{X: c2.X, Y: -c2.Y}
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case canvas.ArcToCmd:
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segment.Verb = GeometryArc
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segment.RadiusX, segment.RadiusY, segment.Rotation, segment.Large, segment.Sweep = scanner.Arc()
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segment.Rotation, segment.Sweep = -segment.Rotation, !segment.Sweep
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case canvas.CloseCmd:
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segment.Verb = GeometryClose
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}
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result = append(result, segment)
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}
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return &result
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}
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// MeasureObject 使用默认解释器度量对象，不分配页面像素
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// 入参: r 渲染器, object 图形对象, options 度量上下文
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// 返回: ObjectMeasurement 度量结果, error 错误信息
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func (CanvasBackend) MeasureObject(r *Renderer, object GraphicObject, options MeasureOptions) (ObjectMeasurement, error) {
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if object.Type != "TextObject" && object.Type != "PathObject" && object.Type != "ImageObject" && object.Type != "CompositeObject" && object.Type != "CompositeGraphicUnit" {
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return ObjectMeasurement{}, fmt.Errorf("unsupported object type %q", object.Type)
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}
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boundary, ctm := editorGeometry(object)
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if _, err := creationBox(boundary); err != nil {
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return ObjectMeasurement{}, err
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}
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if ctm != "" {
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if _, err := creationNumbers(ctm, 6); err != nil {
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return ObjectMeasurement{}, err
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}
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}
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clip, err := canvasGeometryPath(options.Clip)
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if err != nil {
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return ObjectMeasurement{}, err
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}
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bounds := &boundsRenderer{collect: options.Contours}
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renderer := *r
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renderer.pageText = nil
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renderer.textOnly = false
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defaults := options.Defaults
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ctx := canvas.NewContext(bounds)
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switch object.Type {
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case "TextObject":
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if options.Contours {
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renderer.renderText(ctx, object.TextObject, 0, defaults, options.Parent, options.BoundaryInCTM, clip)
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break
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}
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renderer.pageText = &PageText{}
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renderer.textOnly = true
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renderer.renderText(ctx, object.TextObject, 0, defaults, options.Parent, options.BoundaryInCTM, clip)
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var box Box
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for _, run := range renderer.pageText.Runs {
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for _, glyph := range run.Boxes {
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box = unionTextBox(box, glyph)
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}
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}
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return ObjectMeasurement{Bounds: box}, nil
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case "PathObject":
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obj := object.PathObject
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defaults = renderer.drawParamDefaults(obj.DrawParam, defaults)
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obj.DrawParam = ""
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if defaults != nil {
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style := *defaults
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style.FillColor = boundsColor(style.FillColor)
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style.StrokeColor = (*StrokeColor)(boundsColor((*FillColor)(style.StrokeColor)))
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defaults = &style
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}
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obj.FillColor = boundsColor(obj.FillColor)
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obj.StrokeColor = (*StrokeColor)(boundsColor((*FillColor)(obj.StrokeColor)))
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renderer.renderPath(ctx, obj, 0, defaults, options.Parent, options.BoundaryInCTM, clip)
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case "ImageObject":
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renderer.measureImage(ctx, object.ImageObject, 0, options.Parent, options.BoundaryInCTM, clip)
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case "CompositeObject", "CompositeGraphicUnit":
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renderer.renderCompositeGraphicUnit(ctx, object.CompositeGraphicUnit, 0, defaults, options.Parent, options.BoundaryInCTM, clip)
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}
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return ObjectMeasurement{Bounds: bounds.box, Contours: bounds.contours}, nil
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}
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// measureImage 复用图片变换与裁剪语义度量范围，不读取像素数据
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// 入参: ctx 度量画布, obj 图片, pageH 页面高度, parentCTM 父变换, boundaryInCTM 边界是否参与变换, parentClip 父裁剪
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func (r *Renderer) measureImage(ctx *canvas.Context, obj ImageObject, pageH float64, parentCTM *Matrix, boundaryInCTM bool, parentClip *canvas.Path) {
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if obj.Visible != nil && !*obj.Visible || obj.Alpha != nil && *obj.Alpha == 0 {
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return
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}
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box, _ := ParseBox(obj.Boundary)
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ctm := NewMatrix(obj.CTM)
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if obj.CTM == "" {
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ctm = Matrix{a: box.W, d: box.H}
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}
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m := TranslationMatrix(box.X, box.Y).Multiply(ctm)
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if parentCTM != nil {
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if boundaryInCTM {
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m = parentCTM.Multiply(m)
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} else {
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m = TranslationMatrix(box.X, box.Y).Multiply(*parentCTM).Multiply(ctm)
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}
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}
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p := canvas.Rectangle(1, 1).Transform(canvas.Matrix{{m.a, m.c, m.e}, {-m.b, -m.d, pageH - m.f}})
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clip := intersectClipPath(parentClip, r.buildObjectClipPath(obj.Clips, pageH, box.X, box.Y, ctm, parentCTM, boundaryInCTM))
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ctx.Renderer.(*boundsRenderer).add(applyClipPath(p, clip))
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if obj.Border != nil {
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border := *obj.Border
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border.BorderColor = (*StrokeColor)(boundsColor((*FillColor)(border.BorderColor)))
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obj.Border = &border
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r.renderImageBorder(ctx, obj, box, pageH, parentCTM, boundaryInCTM, clip)
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}
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}
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// boundsColor 以底纹的基础颜色和透明度度量轮廓，不修改原画刷
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// 入参: color 填充或描边颜色
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// 返回: *FillColor 用于度量的颜色
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func boundsColor(color *FillColor) *FillColor {
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if color == nil || color.Pattern == nil {
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return color
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}
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return &FillColor{Value: color.Value, Index: color.Index, ColorSpace: color.ColorSpace, Alpha: color.Alpha}
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}
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// boundsRenderer 收集绘制范围，不分配页面像素或合并独立图形轮廓
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type boundsRenderer struct {
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box Box
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collect bool
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contours []ObjectContour
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}
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// Size 返回不限定边界的度量画布尺寸
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// 返回: float64 宽度, float64 高度
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func (r *boundsRenderer) Size() (float64, float64) {
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return 0, 0
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}
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// add 合并路径的精确曲线范围并转换为向下的纵轴
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// 入参: path 绘制路径
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func (r *boundsRenderer) add(path *canvas.Path) {
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r.addContour(path, false)
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}
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// addContour 合并范围并按需保留独立填充区域
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// 入参: path 绘制路径, evenOdd 是否使用奇偶规则
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func (r *boundsRenderer) addContour(path *canvas.Path, evenOdd bool) {
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if path.Empty() {
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return
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}
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rect := path.Bounds()
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r.box = unionTextBox(r.box, Box{X: rect.X0, Y: -rect.Y1, W: rect.W(), H: rect.H()})
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if r.collect {
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outline := &canvas.Path{}
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for _, subpath := range path.Split() {
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subpath = subpath.Copy()
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subpath.Close()
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outline = outline.Append(subpath)
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}
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r.contours = append(r.contours, ObjectContour{Path: outline.Transform(canvas.Matrix{{1, 0, 0}, {0, -1, 0}}).ToSVG(), EvenOdd: evenOdd})
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}
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}
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// RenderPath 收集填充与描边范围，保持线帽、连接和虚线语义
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// 入参: path 路径, style 绘制样式, m 变换矩阵
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func (r *boundsRenderer) RenderPath(path *canvas.Path, style canvas.Style, m canvas.Matrix) {
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if style.HasFill() {
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r.addContour(path.Copy().Transform(m), style.FillRule == canvas.EvenOdd)
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}
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if style.HasStroke() {
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p := path.Dash(style.DashOffset, style.Dashes...).Stroke(style.StrokeWidth, style.StrokeCapper, style.StrokeJoiner, canvas.Tolerance)
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r.add(p.Transform(m))
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}
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}
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// RenderText 收集绘制文字范围
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// 入参: text 文字, m 变换矩阵
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func (r *boundsRenderer) RenderText(text *canvas.Text, m canvas.Matrix) {
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text.RenderTo(r, m, 0)
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}
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// RenderImage 度量不展开底纹图片
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// 入参: img 图片, m 变换矩阵
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func (r *boundsRenderer) RenderImage(img image.Image, m canvas.Matrix) {}
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// PageText 使用默认解释器提取原文与字形位置
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// 入参: r 渲染器, page 页面内容
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// 返回: *PageText 页面文字, error 错误信息
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func (CanvasBackend) PageText(r *Renderer, page *PageContent) (*PageText, error) {
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box, err := r.GetPageBox(page)
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if err != nil {
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return nil, err
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}
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renderer := *r
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renderer.OnPageText = nil
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renderer.pageText = &PageText{}
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renderer.textOnly = true
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if err := renderer.renderPageToContext(canvas.NewContext(canvas.New(box.W, box.H)), page, false); err != nil {
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return nil, err
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}
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return renderer.pageText, nil
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}
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// textPathBox 将字形轮廓转换为页面区域
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// 入参: path 字形轮廓, pageH 页面高度
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// 返回: Box 字符区域
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func textPathBox(path *canvas.Path, pageH float64) Box {
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if path.Empty() {
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return Box{}
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}
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bounds := path.Bounds()
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return Box{X: bounds.X0, Y: pageH - bounds.Y1, W: bounds.X1 - bounds.X0, H: bounds.Y1 - bounds.Y0}
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}
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// addSpan 收集字形选择区域，同一原文区间的多个字形合并为一项
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// 入参: start 起始字符, end 结束字符, bounds 字形布局区域, m 字形变换, clip 裁剪路径, pageH 页面高度
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func (run *TextRun) addSpan(start, end int, bounds canvas.Rect, m canvas.Matrix, clip *canvas.Path, pageH float64) {
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if m.Det() == 0 {
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return
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}
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if clip != nil {
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path := canvas.Rectangle(bounds.W(), bounds.H()).Translate(bounds.X0, bounds.Y0).Transform(m)
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path = applyClipPath(path, clip)
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if path.Empty() {
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return
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}
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bounds = path.Transform(m.Inv()).Bounds()
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}
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if bounds.W() < 0 || bounds.H() <= 0 {
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return
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}
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m = canvas.Matrix{{1, 0, 0}, {0, -1, pageH}}.Mul(m).Translate(bounds.X0, bounds.Y1).Scale(bounds.W(), -bounds.H())
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span := TextSpan{Start: start, End: end}
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if n := len(run.Spans); n > 0 && run.Spans[n-1].Start == start && run.Spans[n-1].End == end {
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span = run.Spans[n-1]
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v := span.Matrix
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previous := canvas.Matrix{{v[0], v[2], v[4]}, {v[1], v[3], v[5]}}
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if previous.Det() != 0 {
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bounds = canvas.Rect{X1: 1, Y1: 1}.Add(canvas.Rect{X1: 1, Y1: 1}.Transform(previous.Inv().Mul(m)))
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m = previous.Translate(bounds.X0, bounds.Y0).Scale(bounds.W(), bounds.H())
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}
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run.Spans = run.Spans[:n-1]
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}
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span.Matrix = [6]float64{m[0][0], m[1][0], m[0][1], m[1][1], m[0][2], m[1][2]}
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run.Spans = append(run.Spans, span)
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}
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