mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-30 01:27:26 +08:00
107 lines
3.1 KiB
Go
107 lines
3.1 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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"bytes"
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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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// preserveImages 按实际绘制顺序恢复颜色及透明度精度，不依赖后端资源命名或对象编号
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// 入参: ctx 取消上下文, data 后端PDF数据
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// 返回: []byte 保留图像精度的PDF数据, error 资源或写入错误
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func (r *pdfRenderer) preserveImages(ctx context.Context, data []byte) ([]byte, error) {
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if !r.exactImages {
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return data, nil
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}
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reader, err := pdfgo.NewReader(bytes.NewReader(data), int64(len(data)))
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if err != nil {
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return nil, err
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}
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defer reader.Close()
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images := make(map[pdfgo.Reference]image.Image)
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pages := 0
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err = reader.WalkPages(ctx, func(index int, page *pdfgo.Page) error {
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if index >= len(r.images) {
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return fmt.Errorf("unexpected PDF output page")
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}
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pages++
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value, err := reader.Resolve(page.Resources["XObject"])
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if err != nil {
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return err
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}
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resources, _ := value.(pdfgo.Dictionary)
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var content bytes.Buffer
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if _, err := page.WriteContent(ctx, &content); err != nil {
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return err
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}
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position := 0
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if err := pdfgo.WalkOperations(ctx, content.Bytes(), func(operation pdfgo.Operation) error {
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if operation.Operator != "Do" {
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return nil
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}
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if len(operation.Operands) != 1 || position >= len(r.images[index]) {
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return fmt.Errorf("unexpected PDF output image")
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}
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name, ok := operation.Operands[0].(pdfgo.Name)
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if !ok {
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return fmt.Errorf("invalid PDF output image name")
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}
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ref, ok := resources[name].(pdfgo.Reference)
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if !ok {
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return fmt.Errorf("invalid PDF output image reference")
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}
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original := r.images[index][position]
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position++
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if original == nil {
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return nil
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}
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image, err := reader.ReadImage(ref)
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if err != nil {
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return err
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}
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if image.Width != original.Bounds().Dx() || image.Height != original.Bounds().Dy() {
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return fmt.Errorf("PDF output image dimensions differ")
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}
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if previous := images[ref]; previous != nil && previous != original {
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return fmt.Errorf("PDF output image reference conflicts")
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}
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images[ref] = original
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return nil
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}); err != nil {
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return err
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}
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if position != len(r.images[index]) {
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return fmt.Errorf("PDF output image missing")
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}
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return nil
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})
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if err != nil {
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return nil, err
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}
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if pages != len(r.images) {
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return nil, fmt.Errorf("PDF output page missing")
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}
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var result bytes.Buffer
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if _, err := reader.ReplaceImagesTo(ctx, &result, images); err != nil {
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return nil, err
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}
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return result.Bytes(), nil
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}
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