mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 17:27:08 +08:00
124 lines
4.0 KiB
Go
124 lines
4.0 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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"crypto/sha256"
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"image"
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"image/color"
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"reflect"
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"github.com/xiaoqidun/pdfgo"
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)
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// pdfImageContentKey 区分编码内容、渲染意图、原生输出空间、模板填充色及有损采样尺寸
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type pdfImageContentKey struct {
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data [32]byte
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intent pdfgo.Name
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process pdfgo.Name
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tint color.NRGBA64
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size image.Point
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}
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// pdfImageContent 保存不依赖间接资源的图像描述及已注册编号
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type pdfImageContent struct {
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source *pdfgo.Image
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id string
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}
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// pdfImageValueBudget 限制图像描述的检查深度和保留字节数
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type pdfImageValueBudget struct {
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nodes int
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bytes int
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}
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// imageContentKey 对无间接依赖的小图像生成内容键，超大图像仍沿用流缓存
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// 入参: source 图像描述, key 流缓存键
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// 返回: pdfImageContentKey 内容键, bool 是否可复用, error 取消错误
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func (p *pdfImporter) imageContentKey(source *pdfgo.Image, key pdfImageKey) (pdfImageContentKey, bool, error) {
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if source == nil || source.Stream == nil || len(source.Stream.Data) > 1<<20 {
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return pdfImageContentKey{}, false, nil
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}
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budget := pdfImageValueBudget{nodes: 256, bytes: 65536}
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for _, value := range []pdfgo.Object{source.Stream.Dictionary, source.ColorSpace, source.Decode, source.Mask, source.SoftMask} {
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if !pdfImageDirectValue(value, &budget) {
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return pdfImageContentKey{}, false, p.ctx.Err()
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}
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}
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hash := sha256.New()
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data := source.Stream.Data
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for len(data) != 0 {
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if err := p.ctx.Err(); err != nil {
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return pdfImageContentKey{}, false, err
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}
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n := min(len(data), 65536)
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hash.Write(data[:n])
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data = data[n:]
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}
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result := pdfImageContentKey{intent: key.intent, process: key.process, tint: key.tint, size: key.size}
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hash.Sum(result.data[:0])
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return result, true, p.ctx.Err()
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}
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// pdfImageDirectValue 检查图像描述是否完全独立，拒绝间接引用和嵌套流
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// 入参: value 描述值, budget 描述检查预算
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// 返回: bool 是否不依赖阅读器资源
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func pdfImageDirectValue(value pdfgo.Object, budget *pdfImageValueBudget) bool {
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if budget.nodes <= 0 || budget.bytes < 64 {
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return false
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}
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budget.nodes--
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budget.bytes -= 64
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switch v := value.(type) {
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case nil, pdfgo.Boolean, pdfgo.Integer, pdfgo.Real:
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return true
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case pdfgo.Name:
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budget.bytes -= len(v)
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return budget.bytes >= 0
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case pdfgo.String:
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budget.bytes -= len(v)
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return budget.bytes >= 0
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case pdfgo.Array:
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for _, child := range v {
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if !pdfImageDirectValue(child, budget) {
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return false
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}
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}
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return true
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case pdfgo.Dictionary:
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for key, child := range v {
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budget.bytes -= len(key)
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if !pdfImageDirectValue(child, budget) {
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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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return false
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}
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// matches 核对完整编码与有效图像属性，不以摘要相同代替内容相同
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// 入参: source 待复用图像
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// 返回: bool 是否可使用同一图像资源
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func (c pdfImageContent) matches(source *pdfgo.Image) bool {
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s := c.source
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return s.Width == source.Width && s.Height == source.Height && s.BitsPerComponent == source.BitsPerComponent &&
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s.ImageMask == source.ImageMask && s.Interpolate == source.Interpolate &&
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bytes.Equal(s.Stream.Data, source.Stream.Data) && reflect.DeepEqual(s.Stream.Dictionary, source.Stream.Dictionary) &&
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reflect.DeepEqual(s.ColorSpace, source.ColorSpace) && reflect.DeepEqual(s.Decode, source.Decode) &&
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reflect.DeepEqual(s.Mask, source.Mask) && reflect.DeepEqual(s.SoftMask, source.SoftMask)
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}
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