mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 16:59:27 +08:00
343 lines
13 KiB
Go
343 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 pdf
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import (
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"context"
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"fmt"
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"image"
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"github.com/xiaoqidun/pdfgo"
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)
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// compositeCancelInterval 保持像素合成的取消检查间隔
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const compositeCancelInterval = 256
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// CompositePixel 保存非预乘源空间分量及累计透明度
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type CompositePixel struct {
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Values [4]float64
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Alpha float64
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Effect float64
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Shape float64
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}
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// transferKey 区分图形状态、网屏覆盖函数及输出设备
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type transferKey struct {
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transfer *pdfgo.TransferFunction
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halftone *pdfgo.Halftone
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model pdfgo.Name
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}
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// TransferCache 在页面内复用设备传递函数，零值可用
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// 缓存与所属阅读器同生命周期，不用于并发解析
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type TransferCache struct {
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functions map[transferKey]*pdfgo.TransferFunction
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}
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// Resolve 在页面内复用输出设备的有效函数，不修改原始图形状态
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// 入参: reader 原始阅读器, style 原始图形状态, model 原生设备颜色空间
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// 返回: *pdfgo.TransferFunction 有效函数, error 网屏传递函数错误
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func (c *TransferCache) Resolve(reader *pdfgo.Reader, style pdfgo.Style, model pdfgo.Name) (*pdfgo.TransferFunction, error) {
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if style.Halftone == nil && style.Transfer == nil {
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return nil, nil
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}
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if model == "" {
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model = "DeviceRGB"
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}
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if c.functions == nil {
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c.functions = make(map[transferKey]*pdfgo.TransferFunction)
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}
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key := transferKey{style.Transfer, style.Halftone, model}
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transfer, found := c.functions[key]
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if !found {
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var err error
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transfer, err = reader.DeviceTransfer(style.Transfer, style.Halftone, model)
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if err != nil {
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return nil, err
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}
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c.functions[key] = transfer
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}
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return transfer, nil
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}
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// OutputColor 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 OutputColor(space *pdfgo.ColorSpace, values [4]float64) ([3]float64, error) {
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return space.SRGB(values[:space.Components()], "RelativeColorimetric")
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}
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// NormalBlend 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 NormalBlend(mode pdfgo.Name) bool {
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return mode == "" || mode == "Normal" || mode == "Compatible"
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}
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// NativePaint 使用库层色料定义求值设备四色，不以备用色代替原生浓度
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// 入参: paint 源画刷, space 设备四色空间, intent 渲染意图
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// 返回: *pdfgo.Paint 原生画刷或nil, [4]bool 显式通道, error 色料定义错误
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func NativePaint(paint pdfgo.Paint, space *pdfgo.ColorSpace, intent pdfgo.Name) (*pdfgo.Paint, [4]bool, error) {
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if paint.Colorant == nil {
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return nil, [4]bool{}, nil
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}
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result, err := paint.Colorant.Space.ResolveInGroup(paint.Colorant.Tints, &pdfgo.ColorantDevice{Space: space}, space, intent, false)
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if err != nil || len(result.Alternates) != 0 {
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return nil, [4]bool{}, err
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}
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return result.Process, result.ProcessMask, nil
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}
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// CompositeColor 将原始画刷变换到混合空间，渐变在源空间求值
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// 入参: paint 画刷, point 页面坐标, space 混合空间, intent 渲染意图, conversion 设备转换函数
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// 返回: [4]float64 混合分量, bool 是否着色, error 颜色错误
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func CompositeColor(paint pdfgo.Paint, point pdfgo.Point, space *pdfgo.ColorSpace, intent pdfgo.Name, conversion pdfgo.ColorConversion) ([4]float64, bool, error) {
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if paint.Shading != nil {
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return [4]float64{}, false, &pdfgo.UnsupportedError{Feature: "local shading pattern compositing"}
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}
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if paint.Tiling != nil {
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return [4]float64{}, false, &pdfgo.UnsupportedError{Feature: "local tiling pattern compositing"}
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}
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var values [4]float64
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var source *pdfgo.ColorSpace
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if paint.Function != nil {
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g := paint.Function
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if g.Bounds != nil {
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inverse, ok := g.PatternMatrix.Inverse()
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if !ok {
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return values, false, fmt.Errorf("singular function shading bounds transform")
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}
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local := inverse.Apply(point)
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if local.X < g.Bounds.XMin || local.X > g.Bounds.XMax || local.Y < g.Bounds.YMin || local.Y > g.Bounds.YMax {
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return values, false, nil
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}
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}
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inverse, ok := g.Matrix.Inverse()
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if !ok {
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return values, false, fmt.Errorf("singular function shading transform")
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}
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local := inverse.Apply(point)
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source, intent = g.Space, g.Intent
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if local.X < g.Domain.XMin || local.X > g.Domain.XMax || local.Y < g.Domain.YMin || local.Y > g.Domain.YMax {
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if g.Background == nil {
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return values, false, nil
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}
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values = *g.Background
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} else {
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var err error
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values, err = g.ValuesAt(local)
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if err != nil {
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return values, false, err
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}
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}
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} else if paint.Axial != nil || paint.Radial != nil {
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var background *[4]float64
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var bounds *pdfgo.Rectangle
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var matrix pdfgo.Matrix
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if g := paint.Axial; g != nil {
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source, intent = g.Space, g.Intent
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background, bounds, matrix = g.Background, g.Bounds, g.Matrix
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} else {
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g := paint.Radial
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source, intent = g.Space, g.Intent
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background, bounds, matrix = g.Background, g.Bounds, g.Matrix
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}
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if bounds != nil {
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local := point
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if matrix != (pdfgo.Matrix{}) {
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inverse, ok := matrix.Inverse()
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if !ok {
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return values, false, fmt.Errorf("singular shading transform")
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}
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local = inverse.Apply(point)
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}
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if local.X < bounds.XMin || local.X > bounds.XMax || local.Y < bounds.YMin || local.Y > bounds.YMax {
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return values, false, nil
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}
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}
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t, visible := ShadingPosition(paint, point)
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var err error
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if !visible {
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if background == nil {
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return values, false, nil
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}
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values = *background
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} else if paint.Axial != nil {
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values, err = paint.Axial.ValuesAt(t)
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} else {
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values, err = paint.Radial.ValuesAt(t)
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}
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if err != nil {
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return values, false, err
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}
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} else if paint.Space != nil {
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values, source = paint.Values, paint.Space
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} else if paint.CMYK != nil {
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values, source = *paint.CMYK, &pdfgo.ColorSpace{Model: "DeviceCMYK"}
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} else if paint.SourceSpace == "DeviceGray" {
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values[0], source = paint.RGB[0], &pdfgo.ColorSpace{Model: "DeviceGray"}
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} else {
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copy(values[:], paint.RGB[:])
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source = &pdfgo.ColorSpace{Model: "DeviceRGB"}
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}
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values, err := space.ConvertWith(values[:source.Components()], source, intent, conversion)
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return values, true, err
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}
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// CompositeInterpolate 按形状覆盖混合预乘颜色及累计透明度
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// 入参: target 原像素与输出, source 替换像素, shape 覆盖率
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// 返回: error 像素或覆盖率错误
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func CompositeInterpolate(target *CompositePixel, source CompositePixel, shape float64) error {
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pixel := pdfgo.ColorantPixel{Values: target.Values[:], Alpha: target.Alpha, Shape: target.Shape, Effect: target.Effect}
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if err := pixel.Interpolate(pdfgo.ColorantPixel{Values: source.Values[:], Alpha: source.Alpha, Shape: source.Shape, Effect: source.Effect}, shape); err != nil {
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return err
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}
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target.Alpha, target.Effect = pixel.Alpha, pixel.Effect
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return nil
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}
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// CompositeKnockout 移除未覆盖区域的初始背景贡献，保留形状与不透明度差异
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// 入参: target 累计组结果, initial 初始背景, source 单个对象合成结果
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// 返回: error 像素错误
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func CompositeKnockout(target *CompositePixel, initial, source CompositePixel) error {
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pixel := pdfgo.ColorantPixel{Values: target.Values[:], Alpha: target.Alpha, Shape: target.Shape, Effect: target.Effect}
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if err := pixel.Knockout(
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pdfgo.ColorantPixel{Values: initial.Values[:], Alpha: initial.Alpha, Shape: initial.Shape, Effect: initial.Effect},
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pdfgo.ColorantPixel{Values: source.Values[:], Alpha: source.Alpha, Shape: source.Shape, Effect: source.Effect},
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); err != nil {
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return err
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}
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target.Alpha, target.Effect, target.Shape = pixel.Alpha, pixel.Effect, pixel.Shape
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return nil
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}
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// CompositeGroupRegion 在组覆盖区域合成像素，保留原栅格及形状贡献
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// 入参: ctx 取消上下文, pixels 父组输出, initial 初始背景, result 组结果, stride 行跨度, region 覆盖区域, space 组空间, parent 父空间, opacity 组不透明度, mask 蒙版, mode 混合模式, intent 渲染意图, conversion 设备转换函数
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// 返回: error 缓冲、区域、颜色或混合错误
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func CompositeGroupRegion(ctx context.Context, pixels, initial, result []CompositePixel, stride int, region image.Rectangle, space, parent *pdfgo.ColorSpace, opacity float64, mask []float64, mode, intent pdfgo.Name, conversion pdfgo.ColorConversion) error {
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if err := ctx.Err(); err != nil {
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return err
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}
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if len(pixels) != len(initial) || len(pixels) != len(result) || mask != nil && len(mask) != len(pixels) {
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return fmt.Errorf("invalid PDF transparency group buffers")
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}
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if stride <= 0 || region.Min.X < 0 || region.Min.Y < 0 || region.Max.X > stride || !region.Empty() && region.Max.Y > len(pixels)/stride {
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return fmt.Errorf("invalid PDF transparency group region")
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}
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group, destination := pdfgo.ColorantGroup{Space: space}, pdfgo.ColorantGroup{Space: parent}
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compositor, err := destination.PrepareGroup(&group, mode, intent, conversion)
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if err != nil {
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return err
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}
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if region.Empty() {
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return nil
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}
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components, parentComponents := space.Components(), parent.Components()
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var target pdfgo.ColorantPixel
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var previous, previousInitial, previousResult, composed CompositePixel
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var previousAlpha float64
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ready := false
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for y := region.Min.Y; y < region.Max.Y; y++ {
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if err := ctx.Err(); err != nil {
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return err
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}
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for i, end := y*stride+region.Min.X, y*stride+region.Max.X; i < end; i++ {
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if i%compositeCancelInterval == 0 {
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if err := ctx.Err(); err != nil {
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return err
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}
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}
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alpha := opacity
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if mask != nil {
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alpha *= mask[i]
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}
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pixel := &result[i]
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if ready && pixels[i] == previous && initial[i] == previousInitial && *pixel == previousResult && alpha == previousAlpha {
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pixels[i] = composed
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continue
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}
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previous, previousInitial, previousResult, previousAlpha = pixels[i], initial[i], *pixel, alpha
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target.Values = pixels[i].Values[:parentComponents]
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target.Alpha = pixels[i].Alpha
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target.Shape = pixels[i].Shape
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target.Effect = pixels[i].Effect
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if err := compositor.Composite(&target,
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pdfgo.ColorantPixel{Values: initial[i].Values[:components], Alpha: initial[i].Alpha, Shape: initial[i].Shape, Effect: initial[i].Effect},
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pdfgo.ColorantPixel{Values: pixel.Values[:components], Alpha: pixel.Alpha, Shape: pixel.Shape, Effect: pixel.Effect},
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alpha,
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); err != nil {
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return err
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}
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pixels[i].Alpha, pixels[i].Effect, pixels[i].Shape = target.Alpha, target.Effect, target.Shape
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composed, ready = pixels[i], true
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}
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}
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return nil
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}
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// CompositePaintOver 以兼容叠印计算零色料分量，再应用对象混合模式
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// 入参: backdrop 背景及输出, source 源分量, alpha 源透明度, space 混合空间, mode 混合模式, compatible 是否保留零色料背景, marked 原生过程通道，nil使用普通空间
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// 返回: error 未支持的混合模式
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func CompositePaintOver(backdrop *CompositePixel, source [4]float64, alpha float64, space *pdfgo.ColorSpace, mode pdfgo.Name, compatible bool, marked *[4]bool) error {
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if !compatible && marked == nil {
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return CompositeOver(backdrop, source, alpha, space, mode)
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}
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if alpha == 0 {
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return nil
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}
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mask := PaintChannels(source, compatible, marked)
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values, combined, err := space.CompositeOverprint(backdrop.Values[:space.Components()], source[:space.Components()], backdrop.Alpha, alpha, mode, mask[:space.Components()])
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if err != nil {
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return err
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}
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copy(backdrop.Values[:space.Components()], values[:space.Components()])
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backdrop.Alpha = combined
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backdrop.Effect = alpha + backdrop.Effect*(1-alpha)
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return nil
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}
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// CompositeOver 按PDF透明模型合成源颜色，四色混合使用分量补色
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// 入参: backdrop 背景及输出, source 源分量, alpha 源透明度, space 混合空间, mode 混合模式
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// 返回: error 未支持的混合模式
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func CompositeOver(backdrop *CompositePixel, source [4]float64, alpha float64, space *pdfgo.ColorSpace, mode pdfgo.Name) error {
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if alpha == 0 {
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return nil
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}
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values, combined, err := space.Composite(backdrop.Values[:space.Components()], source[:space.Components()], backdrop.Alpha, alpha, mode)
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if err != nil {
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return err
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}
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copy(backdrop.Values[:space.Components()], values[:space.Components()])
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backdrop.Alpha = combined
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backdrop.Effect = alpha + backdrop.Effect*(1-alpha)
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return nil
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}
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// PaintChannels 选择兼容叠印实际使用源颜色的通道
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// 入参: values 源四色分量, compatible 是否保留零分量背景, marked 指定通道，nil表示全部
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// 返回: [4]bool 各通道是否取源颜色
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func PaintChannels(values [4]float64, compatible bool, marked *[4]bool) [4]bool {
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channels := [4]bool{true, true, true, true}
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if marked != nil {
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channels = *marked
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}
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if compatible {
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for i := range channels {
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channels[i] = channels[i] && values[i] != 0
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}
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}
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return channels
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}
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