mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-30 01:27:26 +08:00
395 lines
13 KiB
Go
395 lines
13 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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"math"
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"github.com/xiaoqidun/pdfgo"
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)
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// pdfCompositeNode 保留局部合成所需的原始图元和透明组层级
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type pdfCompositeNode struct {
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path *pdfgo.PathMark
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text *pdfgo.TextMark
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image *pdfgo.ImageMark
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group *pdfgo.GroupMark
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children []pdfCompositeNode
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}
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// pdfCompositePixel 保存非预乘源空间分量及累计透明度
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type pdfCompositePixel struct {
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values [4]float64
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alpha float64
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effect float64
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}
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// pdfCompositor 在指定局部区域中按源颜色空间合成PDF图元
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type pdfCompositor struct {
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importer *pdfImporter
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box Box
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width, height int
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inverse pdfgo.Matrix
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cache *pdfCompositeCache
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masks map[*pdfgo.SoftMask][]float64
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}
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// pdfCompositeKey 区分图元的填充与描边几何
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type pdfCompositeKey struct {
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path *pdfgo.PathMark
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text *pdfgo.TextMark
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image *pdfgo.ImageMark
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stroke bool
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}
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// pdfCompositeGeometry 保存后端中立的绘制命令及其页面边界
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type pdfCompositeGeometry struct {
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scene *RasterPage
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box Box
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}
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// pdfCompositeCache 在单页内复用几何、图像分量及蒙版内容
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type pdfCompositeCache struct {
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geometry map[pdfCompositeKey]pdfCompositeGeometry
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images map[*pdfgo.Image]*pdfgo.ImageComponents
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masks map[*pdfgo.SoftMask][]pdfCompositeNode
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}
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// compositingCache 按需创建单页合成缓存，页面切换时由导入器释放
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// 返回: *pdfCompositeCache 当前页面缓存
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func (p *pdfImporter) compositingCache() *pdfCompositeCache {
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if p.compositeCache == nil {
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p.compositeCache = &pdfCompositeCache{geometry: map[pdfCompositeKey]pdfCompositeGeometry{}, images: map[*pdfgo.Image]*pdfgo.ImageComponents{}, masks: map[*pdfgo.SoftMask][]pdfCompositeNode{}}
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}
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return p.compositeCache
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}
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// coverage 复用已编译的覆盖场景，跳过与当前区域无交集的图元
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// 入参: node 图元, stroke 是否描边
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// 返回: image.Image 当前区域覆盖或空值, error 编译或渲染错误
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func (c *pdfCompositor) coverage(node pdfCompositeNode, stroke bool) (image.Image, error) {
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if node.text != nil && len(node.text.Font.Program) == 0 && node.text.Font.BoundingBox != nil {
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b := c.importer.compositeTextBounds(*node.text, stroke)
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if b.X >= c.box.X+c.box.W || b.Y >= c.box.Y+c.box.H || b.X+b.W <= c.box.X || b.Y+b.H <= c.box.Y {
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return nil, nil
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}
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}
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key := pdfCompositeKey{path: node.path, text: node.text, image: node.image, stroke: stroke}
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geometry, ok := c.cache.geometry[key]
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if !ok {
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var err error
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geometry.scene, geometry.box, err = c.importer.compileGroup(func(local *pdfImporter) error { return node.coverage(local, stroke) })
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if err != nil {
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return nil, err
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}
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c.cache.geometry[key] = geometry
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}
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b := geometry.box
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if geometry.scene == nil || b.X >= c.box.X+c.box.W || b.Y >= c.box.Y+c.box.H || b.X+b.W <= c.box.X || b.Y+b.H <= c.box.Y {
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return nil, nil
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}
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return c.importer.renderGroupScene(geometry.scene, c.box)
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}
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// compositeTextBounds 按字体描述符计算保守边界，仅用于排除不相交的外部字体
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// 入参: mark 具有字体边界的文字, stroke 是否描边
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// 返回: Box 包含描边和抗锯齿边缘的页面范围
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func (p *pdfImporter) compositeTextBounds(mark pdfgo.TextMark, stroke bool) Box {
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b := mark.Font.BoundingBox
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matrix := p.matrix.Mul(mark.Matrix)
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var points []pdfgo.Point
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for _, origin := range mark.Positions {
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for _, point := range []pdfgo.Point{{X: b.XMin, Y: b.YMin}, {X: b.XMax, Y: b.YMin}, {X: b.XMax, Y: b.YMax}, {X: b.XMin, Y: b.YMax}} {
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points = append(points, matrix.Apply(pdfgo.Point{X: origin.X + point.X*mark.Size*mark.HorizontalScale/1000, Y: origin.Y + point.Y*mark.Size/1000}))
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}
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}
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box := pdfBounds(points)
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marginX, marginY := 25.4/p.rasterDPI, 25.4/p.rasterDPI
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if stroke {
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m := mark.StrokeMatrix
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if m == (pdfgo.Matrix{}) {
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m = pdfgo.Identity()
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}
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m = p.matrix.Mul(m)
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distance := mark.Style.LineWidth / 2 * math.Max(1, mark.Style.MiterLimit)
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marginX += distance * (math.Abs(m[0]) + math.Abs(m[2]))
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marginY += distance * (math.Abs(m[1]) + math.Abs(m[3]))
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}
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return Box{X: box.X - marginX, Y: box.Y - marginY, W: box.W + 2*marginX, H: box.H + 2*marginY}
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}
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// pdfCompositeNodes 收集原始绘制顺序，语义警告只在首次解析时交付
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// 入参: walk 内容访问函数, warning 警告回调
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// 返回: []pdfCompositeNode 原始图元, error 解析错误
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func pdfCompositeNodes(walk func(pdfgo.Visitor) error, warning func(pdfgo.Diagnostic)) ([]pdfCompositeNode, error) {
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var nodes []pdfCompositeNode
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v := pdfgo.Visitor{Warning: warning}
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v.Path = func(mark pdfgo.PathMark) error { nodes = append(nodes, pdfCompositeNode{path: &mark}); return nil }
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v.Text = func(mark pdfgo.TextMark) error { nodes = append(nodes, pdfCompositeNode{text: &mark}); return nil }
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v.Image = func(mark pdfgo.ImageMark) error { nodes = append(nodes, pdfCompositeNode{image: &mark}); return nil }
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v.Group = func(mark pdfgo.GroupMark, walk func(pdfgo.Visitor) error) error {
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children, err := pdfCompositeNodes(walk, warning)
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if err != nil {
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return err
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}
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nodes = append(nodes, pdfCompositeNode{group: &mark, children: children})
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return nil
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}
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err := walk(v)
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return nodes, err
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}
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// compositePage 保留独立不透明对象，仅将需要背景参与的效果在局部区域合成
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// 入参: space 页面混合空间, walk 页面内容
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// 返回: error 转换错误
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func (p *pdfImporter) compositePage(space *pdfgo.ColorSpace, walk func(pdfgo.Visitor) error) error {
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nodes, err := pdfCompositeNodes(walk, p.warning)
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if err != nil {
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return err
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}
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for i, node := range nodes {
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if node.opaque(space) {
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if err := node.emit(p.visitor()); err != nil {
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return fmt.Errorf("convert graphic %d: %w", i+1, err)
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}
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} else {
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if p.warning == nil {
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return &pdfgo.UnsupportedError{Feature: "page color-space compositing"}
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}
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if err := p.flushPath(); err != nil {
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return err
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}
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if err := p.compositeRegion(nodes[:i], node, space, true); err != nil {
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return fmt.Errorf("composite graphic %d: %w", i+1, err)
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}
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}
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}
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return p.flushPath()
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}
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// opaque 检查图元是否无需与页面背景混合
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// 入参: space 当前混合空间
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// 返回: bool 是否可直接保留
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func (n pdfCompositeNode) opaque(space *pdfgo.ColorSpace) bool {
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if n.group != nil {
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g := n.group
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if g.Alpha != 1 || g.SoftMask != nil || !pdfNormalBlend(g.BlendMode) || g.ColorSpace != nil && !g.ColorSpace.Equal(space) {
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return false
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}
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for _, child := range n.children {
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if !child.opaque(space) {
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return false
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}
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}
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return true
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}
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style, fill, stroke := n.style()
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if style.SoftMask != nil || !pdfNormalBlend(style.BlendMode) || fill && style.Fill.Alpha != 1 || stroke && style.Stroke.Alpha != 1 {
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return false
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}
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if fill && style.FillOverprint && pdfOverprintNeedsSeparation(style.Fill) || stroke && style.StrokeOverprint && pdfOverprintNeedsSeparation(style.Stroke) {
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return false
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}
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if fill && pdfGradientError(style.Fill) != nil || stroke && pdfGradientError(style.Stroke) != nil {
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return false
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}
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if n.image != nil && (n.image.Image.Mask != nil || n.image.Image.SoftMask != nil) {
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return false
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}
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return true
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}
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// style 获取图元实际使用的图形状态
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// 返回: pdfgo.Style 图形状态, bool 是否填充, bool 是否描边
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func (n pdfCompositeNode) style() (pdfgo.Style, bool, bool) {
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if n.path != nil {
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return n.path.Style, n.path.Fill, n.path.Stroke
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}
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if n.text != nil {
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mode := n.text.Mode % 4
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return n.text.Style, mode == 0 || mode == 2, mode == 1 || mode == 2
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}
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return n.image.Style, true, false
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}
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// emit 向现有转换器交付原始图元
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// 入参: visitor 图元访问器
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// 返回: error 转换错误
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func (n pdfCompositeNode) emit(visitor pdfgo.Visitor) error {
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if n.path != nil {
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return visitor.Path(*n.path)
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}
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if n.text != nil {
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return visitor.Text(*n.text)
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}
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if n.image != nil {
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return visitor.Image(*n.image)
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}
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return visitor.Group(*n.group, func(v pdfgo.Visitor) error {
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for _, child := range n.children {
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if err := child.emit(v); err != nil {
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return err
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}
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}
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return nil
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})
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}
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// coverage 构建白色几何覆盖，颜色和透明度由合成器单独计算
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// 入参: p 局部导入器, stroke 是否只取描边
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// 返回: error 几何错误
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func (n pdfCompositeNode) coverage(p *pdfImporter, stroke bool) error {
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if n.group != nil {
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for _, child := range n.children {
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if child.group != nil {
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if err := child.coverage(p, false); err != nil {
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return err
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}
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continue
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}
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_, fill, hasStroke := child.style()
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if fill {
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if err := child.coverage(p, false); err != nil {
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return err
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}
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}
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if hasStroke {
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if err := child.coverage(p, true); err != nil {
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return err
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}
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}
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}
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return nil
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}
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style, _, _ := n.style()
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style.Fill, style.Stroke = pdfgo.Paint{RGB: [3]float64{1, 1, 1}, Alpha: 1}, pdfgo.Paint{RGB: [3]float64{1, 1, 1}, Alpha: 1}
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style.SoftMask, style.BlendMode = nil, "Normal"
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style.FillOverprint, style.StrokeOverprint = false, false
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if n.path != nil {
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mark := *n.path
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mark.Style = style
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mark.Fill, mark.Stroke = !stroke, stroke
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return p.path(mark)
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}
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if n.text != nil {
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mark := *n.text
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mark.Style = style
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mark.Mode = 0
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if stroke {
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mark.Mode = 1
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}
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return p.text(mark)
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}
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mark := n.image
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path := pdfgo.Path{Segments: []pdfgo.Segment{
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{Operator: "M", Points: []pdfgo.Point{mark.Matrix.Apply(pdfgo.Point{})}},
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{Operator: "L", Points: []pdfgo.Point{mark.Matrix.Apply(pdfgo.Point{X: 1})}},
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{Operator: "L", Points: []pdfgo.Point{mark.Matrix.Apply(pdfgo.Point{X: 1, Y: 1})}},
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{Operator: "L", Points: []pdfgo.Point{mark.Matrix.Apply(pdfgo.Point{Y: 1})}},
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{Operator: "C"},
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}}
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return p.path(pdfgo.PathMark{Path: path, Style: style, Fill: true})
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}
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// compositeRegion 按原始背景计算局部效果，不将组外文字和图形栅格化
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// 入参: backdrop 前序图元, node 当前效果, space 页面混合空间, flatten 是否合并页面背景
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// 返回: error 合成或保存错误
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func (p *pdfImporter) compositeRegion(backdrop []pdfCompositeNode, node pdfCompositeNode, space *pdfgo.ColorSpace, flatten bool) error {
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scene, box, err := p.compileGroup(func(local *pdfImporter) error {
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if node.group != nil {
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return node.coverage(local, false)
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}
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_, fill, stroke := node.style()
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if fill {
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if err := node.coverage(local, false); err != nil {
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return err
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}
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}
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if stroke {
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return node.coverage(local, true)
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}
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return nil
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})
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if err != nil || scene == nil {
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return err
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}
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inverse, ok := p.matrix.Inverse()
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if !ok {
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return fmt.Errorf("invalid PDF compositing transform")
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}
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w, h, err := (&RasterPage{Width: box.W, Height: box.H, DPI: p.rasterDPI}).PixelSize()
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if err != nil {
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return err
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}
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output := image.NewNRGBA(image.Rect(0, 0, w, h))
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cache := p.compositingCache()
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step := 25.4 / p.rasterDPI
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for y := 0; y < h; y += 256 {
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for x := 0; x < w; x += 256 {
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width, height := min(256, w-x), min(256, h-y)
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c := pdfCompositor{importer: p, box: Box{X: box.X + float64(x)*step, Y: box.Y + float64(y)*step, W: float64(width) * step, H: float64(height) * step}, width: width, height: height, inverse: inverse, cache: cache, masks: map[*pdfgo.SoftMask][]float64{}}
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pixels := make([]pdfCompositePixel, width*height)
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if err := c.draw(backdrop, pixels, space); err != nil {
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return err
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}
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for i := range pixels {
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pixels[i].effect = 0
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}
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if err := c.draw([]pdfCompositeNode{node}, pixels, space); err != nil {
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return err
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}
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for i, pixel := range pixels {
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if pixel.effect == 0 {
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continue
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}
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rgb, err := pdfCompositeOutputColor(space, pixel.values)
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if err != nil {
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return err
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}
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alpha := pixel.alpha
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if flatten {
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for j := range rgb {
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rgb[j] = pixel.alpha*rgb[j] + 1 - pixel.alpha
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}
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alpha = 1
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}
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output.SetNRGBA(x+i%width, y+i/width, color.NRGBA{R: uint8(math.Round(rgb[0] * 255)), G: uint8(math.Round(rgb[1] * 255)), B: uint8(math.Round(rgb[2] * 255)), A: uint8(math.Round(alpha * 255))})
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}
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}
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}
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return p.appendRasterGroup(output, box, 1)
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}
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// pdfCompositeOutputColor 将合成结果映射到OFD输出，与保留的设备四色对象使用相同显示换算
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// 入参: space 合成空间, values 非预乘分量
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// 返回: [3]float64 显示颜色, error 校准颜色转换错误
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func pdfCompositeOutputColor(space *pdfgo.ColorSpace, values [4]float64) ([3]float64, error) {
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if space.Model == "DeviceCMYK" && !space.Calibrated() {
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black := 1 - values[3]
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return [3]float64{(1 - values[0]) * black, (1 - values[1]) * black, (1 - values[2]) * black}, nil
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}
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return space.RGB(values[:space.Components()], "RelativeColorimetric")
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}
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// pdfNormalBlend 判断混合模式是否为普通覆盖
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// 入参: mode 混合模式
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// 返回: bool 是否普通覆盖
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func pdfNormalBlend(mode pdfgo.Name) bool {
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return mode == "" || mode == "Normal" || mode == "Compatible"
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}
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