mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-30 01:27:26 +08:00
217 lines
6.7 KiB
Go
217 lines
6.7 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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"math"
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"github.com/xiaoqidun/pdfgo"
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)
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// pdfMeshVertex 保存局部毫米坐标及原曲面参数
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type pdfMeshVertex struct {
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point pdfgo.Point
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u, v float64
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}
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// pdfMeshTriangle 保存按输出精度细分的曲面网格
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type pdfMeshTriangle struct {
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vertices [3]pdfMeshVertex
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patch int
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}
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// pdfMeshKey 区分网格及其输出混合空间
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type pdfMeshKey struct {
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mesh *pdfgo.MeshGradient
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space *pdfgo.ColorSpace
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}
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// pdfMeshPixel 保存抗锯齿覆盖率与源空间合成分量
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type pdfMeshPixel struct {
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values [4]float64
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shape float64
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}
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// pdfMeshSample 保存采样点参数，patch为一基编号，零表示未覆盖
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type pdfMeshSample struct {
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u, v float64
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patch int
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}
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// meshTriangles 按曲面二阶导数界细分，将几何误差控制在输出像素的十六分之一内
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// 入参: mesh 原始曲面
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// 返回: []pdfMeshTriangle 细分结果, error 取消或坐标错误
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func (p *pdfImporter) meshTriangles(mesh *pdfgo.MeshGradient) ([]pdfMeshTriangle, error) {
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matrix := p.matrix.Mul(mesh.Matrix)
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var triangles []pdfMeshTriangle
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for index, patch := range mesh.Patches {
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for i := range patch.Points {
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for j := range patch.Points[i] {
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patch.Points[i][j] = matrix.Apply(patch.Points[i][j])
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}
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}
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var duu, dvv, duv float64
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for i := 0; i < 4; i++ {
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for j := 0; j < 4; j++ {
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a := patch.Points[i][j]
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if i < 2 {
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b, c := patch.Points[i+1][j], patch.Points[i+2][j]
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duu = math.Max(duu, 6*math.Hypot(c.X-2*b.X+a.X, c.Y-2*b.Y+a.Y))
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}
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if j < 2 {
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b, c := patch.Points[i][j+1], patch.Points[i][j+2]
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dvv = math.Max(dvv, 6*math.Hypot(c.X-2*b.X+a.X, c.Y-2*b.Y+a.Y))
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}
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if i < 3 && j < 3 {
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b, c, d := patch.Points[i+1][j], patch.Points[i][j+1], patch.Points[i+1][j+1]
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duv = math.Max(duv, 9*math.Hypot(d.X-b.X-c.X+a.X, d.Y-b.Y-c.Y+a.Y))
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}
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}
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}
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steps := math.Max(1, math.Ceil(math.Sqrt(8*(duu+dvv+2*duv)*p.rasterDPI/25.4)))
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if !finite(steps) || steps >= math.Sqrt(float64(int(^uint(0)>>1)/2)) {
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return nil, fmt.Errorf("mesh subdivision exceeds platform integer range")
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}
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n := int(steps)
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row := make([]pdfMeshVertex, n+1)
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for i := range row {
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u := float64(i) / steps
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row[i] = pdfMeshVertex{patch.PointAt(u, 0), u, 0}
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}
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for j := 1; j <= n; j++ {
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if err := p.ctx.Err(); err != nil {
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return nil, err
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}
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v := float64(j) / steps
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left := pdfMeshVertex{patch.PointAt(0, v), 0, v}
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for i := 1; i <= n; i++ {
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u := float64(i) / steps
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right := pdfMeshVertex{patch.PointAt(u, v), u, v}
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a, b := row[i-1], row[i]
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triangles = append(triangles, pdfMeshTriangle{[3]pdfMeshVertex{a, b, left}, index}, pdfMeshTriangle{[3]pdfMeshVertex{b, right, left}, index})
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row[i-1], left = left, right
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}
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row[n] = left
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}
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}
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return triangles, nil
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}
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// mesh 对当前图块执行四倍超采样，曲面重叠按后补片及较大v、u取值
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// 入参: mesh 原曲面, space 输出混合空间
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// 返回: []pdfMeshPixel 颜色及覆盖, error 几何或颜色错误
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func (c *pdfCompositor) mesh(mesh *pdfgo.MeshGradient, space *pdfgo.ColorSpace) ([]pdfMeshPixel, error) {
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key := pdfMeshKey{mesh, space}
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if pixels, ok := c.meshes[key]; ok {
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return pixels, nil
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}
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triangles, ok := c.cache.meshes[mesh]
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if !ok {
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var err error
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triangles, err = c.importer.meshTriangles(mesh)
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if err != nil {
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return nil, err
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}
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if c.cache.meshes == nil {
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c.cache.meshes = map[*pdfgo.MeshGradient][]pdfMeshTriangle{}
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}
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c.cache.meshes[mesh] = triangles
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}
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const samples = 4
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w, h := c.width*samples, c.height*samples
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grid := make([]pdfMeshSample, w*h)
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scale := c.importer.rasterDPI / 25.4 * samples
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for _, triangle := range triangles {
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if err := c.importer.ctx.Err(); err != nil {
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return nil, err
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}
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vertices := triangle.vertices
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for i := range vertices {
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vertices[i].point.X = (vertices[i].point.X - c.box.X) * scale
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vertices[i].point.Y = (vertices[i].point.Y - c.box.Y) * scale
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}
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a, b, d := vertices[0].point, vertices[1].point, vertices[2].point
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denominator := (b.Y-d.Y)*(a.X-d.X) + (d.X-b.X)*(a.Y-d.Y)
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if denominator == 0 {
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continue
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}
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minX, maxX := math.Min(a.X, math.Min(b.X, d.X)), math.Max(a.X, math.Max(b.X, d.X))
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minY, maxY := math.Min(a.Y, math.Min(b.Y, d.Y)), math.Max(a.Y, math.Max(b.Y, d.Y))
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if maxX < 0 || maxY < 0 || minX >= float64(w) || minY >= float64(h) {
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continue
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}
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endX := int(math.Min(float64(w), math.Ceil(maxX)))
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endY := int(math.Min(float64(h), math.Ceil(maxY)))
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for y := int(math.Max(0, math.Floor(minY))); y < endY; y++ {
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for x := int(math.Max(0, math.Floor(minX))); x < endX; x++ {
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px, py := float64(x)+.5, float64(y)+.5
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l0 := ((b.Y-d.Y)*(px-d.X) + (d.X-b.X)*(py-d.Y)) / denominator
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l1 := ((d.Y-a.Y)*(px-d.X) + (a.X-d.X)*(py-d.Y)) / denominator
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l2 := 1 - l0 - l1
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if l0 < -1e-10 || l1 < -1e-10 || l2 < -1e-10 {
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continue
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}
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u := math.Max(0, math.Min(1, l0*vertices[0].u+l1*vertices[1].u+l2*vertices[2].u))
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v := math.Max(0, math.Min(1, l0*vertices[0].v+l1*vertices[1].v+l2*vertices[2].v))
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current := &grid[y*w+x]
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if triangle.patch+1 > current.patch || triangle.patch+1 == current.patch && (v > current.v || v == current.v && u > current.u) {
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*current = pdfMeshSample{u, v, triangle.patch + 1}
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}
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}
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}
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}
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pixels := make([]pdfMeshPixel, c.width*c.height)
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for y := 0; y < h; y++ {
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if err := c.importer.ctx.Err(); err != nil {
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return nil, err
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}
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for x := 0; x < w; x++ {
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sample := grid[y*w+x]
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if sample.patch == 0 {
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continue
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}
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values, err := mesh.ValuesAt(sample.patch-1, sample.u, sample.v)
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if err != nil {
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return nil, err
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}
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values, err = space.Convert(values[:mesh.Space.Components()], mesh.Space, mesh.Intent)
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if err != nil {
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return nil, err
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}
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pixel := &pixels[(y/samples)*c.width+x/samples]
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for i, value := range values {
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pixel.values[i] += value
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}
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pixel.shape++
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}
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}
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for i := range pixels {
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pixel := &pixels[i]
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if pixel.shape == 0 {
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continue
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}
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for j := range pixel.values {
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pixel.values[j] /= pixel.shape
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}
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pixel.shape /= samples * samples
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}
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if c.meshes == nil {
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c.meshes = map[pdfMeshKey][]pdfMeshPixel{}
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}
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c.meshes[key] = pixels
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return pixels, nil
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}
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