Files
ofdgo/ofdgo_extract_image.go
T
2026-10-14 08:22:31 +08:00

296 lines
8.6 KiB
Go

// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ofdgo
import (
"archive/zip"
"bytes"
"context"
"encoding/xml"
"fmt"
"io"
"path"
"slices"
"strings"
)
// ImageInfo 描述文档内的原始图片资源,独立蒙版保留为独立资源
// 不包含对象裁剪、旋转、透明度及显示尺寸,不代表页面合成后的外观
type ImageInfo struct {
ID string `json:"id"`
Name string `json:"name"`
Format string `json:"format"`
Location string `json:"-"`
}
// imageOutput 在分块写出图片时检查调用方取消状态
type imageOutput struct {
context context.Context
writer io.Writer
}
// imageInput 在读取资源数据时检查调用方取消状态
type imageInput struct {
io.ReadCloser
context context.Context
}
// imageResourceKey 合并有效十进制标识,非标准标识保留原值,不相互混淆
// 入参: id 图片标识
// 返回: string 查找键
func imageResourceKey(id string) string {
if key := editorResourceID(id); key != "" {
return key
}
return id
}
// Read 检查取消状态后读取原始数据
// 入参: data 数据缓冲区
// 返回: int 读取字节数, error 读取或取消错误
func (r imageInput) Read(data []byte) (int, error) {
if err := r.context.Err(); err != nil {
return 0, err
}
return r.ReadCloser.Read(data)
}
// Write 检查取消状态后写出原始数据
// 入参: data 数据块
// 返回: int 写入字节数, error 写入或取消错误
func (w imageOutput) Write(data []byte) (int, error) {
if err := w.context.Err(); err != nil {
return 0, err
}
return w.writer.Write(data)
}
// Images 列出文档、页面和模板声明的图片资源,不解码图片像素
// 包含未使用及重复引用的资源声明,同一资源标识只返回一次,不加载注解或签名
// 入参: ctx 取消上下文
// 返回: []ImageInfo 图片资源, error 读取或取消错误
func (r *Reader) Images(ctx context.Context) ([]ImageInfo, error) {
if err := ctx.Err(); err != nil {
return nil, err
}
if r.imageCatalog != nil {
return slices.Clone(r.imageCatalog), nil
}
doc, err := r.docStructureContext(ctx)
if err != nil {
return nil, err
}
resources := make([]string, 0)
for _, name := range append(slices.Clone(doc.CommonData.DocumentRes), doc.CommonData.PublicRes...) {
resources = append(resources, r.ResPath(name))
}
pages := slices.Clone(doc.Pages.Page)
for _, template := range doc.CommonData.TemplatePage {
pages = append(pages, Page{BaseLoc: template.BaseLoc})
}
for _, page := range pages {
if err := ctx.Err(); err != nil {
return nil, err
}
header, err := r.readPageHeaderContext(ctx, page)
if err != nil {
return nil, err
}
for _, name := range header.PageRes {
resources = append(resources, resolveResourcePath(r.ResPath(page.BaseLoc), "", name))
}
}
seen := make(map[string]bool)
ids := make(map[string]ImageInfo)
items := make([]ImageInfo, 0)
for _, name := range resources {
if err := ctx.Err(); err != nil {
return nil, err
}
if seen[name] {
continue
}
seen[name] = true
data, err := r.readFileViewContext(ctx, name)
if err != nil {
return nil, err
}
var res Res
decoder := xml.NewDecoder(imageInput{ReadCloser: io.NopCloser(bytes.NewReader(data)), context: ctx})
if err := decoder.Decode(&res); err != nil {
return nil, err
}
for _, media := range res.MultiMedias.MultiMedia {
if err := ctx.Err(); err != nil {
return nil, err
}
if media.Type != "Image" {
continue
}
location := resolveResourcePath(name, res.BaseLoc, media.MediaFile)
if media.ID == "" || location == "" {
return nil, fmt.Errorf("invalid image resource")
}
item := ImageInfo{ID: media.ID, Name: path.Base(location), Format: media.Format, Location: location}
key := imageResourceKey(item.ID)
if previous, ok := ids[key]; ok {
if previous.Name != item.Name || previous.Format != item.Format || previous.Location != item.Location {
return nil, fmt.Errorf("conflicting image resource %q", item.ID)
}
continue
}
ids[key] = item
items = append(items, item)
}
}
if err := ctx.Err(); err != nil {
return nil, err
}
r.imageCatalog = items
return slices.Clone(items), nil
}
// Image 查找指定图片,复用媒体索引或图片清单,尚未建立索引时读取资源声明
// 入参: ctx 取消上下文, id 图片资源标识
// 返回: ImageInfo 图片资源, error 读取或取消错误
func (r *Reader) Image(ctx context.Context, id string) (ImageInfo, error) {
if err := ctx.Err(); err != nil {
return ImageInfo{}, err
}
name, _ := resourceValue(r.resourceFiles, id)
if name != "" {
if r.resourcesRead[name] {
if media, ok := resourceValue(r.mediaCache, id); ok && media.Type == "Image" && media.MediaFile != "" {
location := r.ResPath(media.MediaFile)
if err := ctx.Err(); err != nil {
return ImageInfo{}, err
}
return ImageInfo{ID: id, Name: path.Base(location), Format: media.Format, Location: location}, nil
}
}
data, err := r.readFileViewContext(ctx, name)
if err != nil {
return ImageInfo{}, err
}
var res Res
decoder := xml.NewDecoder(imageInput{ReadCloser: io.NopCloser(bytes.NewReader(data)), context: ctx})
if err := decoder.Decode(&res); err != nil {
return ImageInfo{}, err
}
for _, media := range res.MultiMedias.MultiMedia {
if err := ctx.Err(); err != nil {
return ImageInfo{}, err
}
if imageResourceKey(media.ID) == imageResourceKey(id) && media.Type == "Image" && media.MediaFile != "" {
location := resolveResourcePath(name, res.BaseLoc, media.MediaFile)
return ImageInfo{ID: id, Name: path.Base(location), Format: media.Format, Location: location}, nil
}
}
return ImageInfo{}, fmt.Errorf("image resource %q not found", id)
}
items := r.imageCatalog
if items == nil {
var err error
items, err = r.Images(ctx)
if err != nil {
return ImageInfo{}, err
}
}
key := imageResourceKey(id)
for _, item := range items {
if err := ctx.Err(); err != nil {
return ImageInfo{}, err
}
if imageResourceKey(item.ID) == key {
return item, nil
}
}
return ImageInfo{}, fmt.Errorf("image resource %q not found", id)
}
// OpenImage 打开原始图片资源流,不解码、不重采样或重新压缩
// 加密文档返回解密后的资源,调用方负责关闭并完整读取以校验ZIP数据
// 入参: ctx 取消上下文, id 图片资源标识
// 返回: io.ReadCloser 原始图片流, error 读取错误
func (r *Reader) OpenImage(ctx context.Context, id string) (io.ReadCloser, error) {
item, err := r.Image(ctx, id)
if err != nil {
return nil, err
}
input, err := r.openFile(item.Location)
if err != nil {
return nil, err
}
return imageInput{ReadCloser: input, context: ctx}, nil
}
// WriteImages 将原始图片逐个写入ZIP,不改变图片编码,文件序号避免同名覆盖
// 入参: ctx 取消上下文, writer 输出流, ids 资源标识,省略则导出全部
// 返回: error 读取、写出或取消错误
func (r *Reader) WriteImages(ctx context.Context, writer io.Writer, ids ...string) error {
var items []ImageInfo
if len(ids) == 0 {
var err error
items, err = r.Images(ctx)
if err != nil {
return err
}
} else {
seen := make(map[string]bool)
for _, id := range ids {
key := imageResourceKey(id)
if seen[key] {
continue
}
item, err := r.Image(ctx, id)
if err != nil {
return err
}
items = append(items, item)
seen[key] = true
}
}
archive := zip.NewWriter(imageOutput{ctx, writer})
for i, item := range items {
if err := ctx.Err(); err != nil {
return err
}
name := strings.Map(func(c rune) rune {
if c < 32 || strings.ContainsRune(`<>:"/\|?*`, c) {
return '_'
}
return c
}, item.Name)
header := &zip.FileHeader{Name: fmt.Sprintf("%04d-%s", i+1, name), Method: zip.Store}
output, err := archive.CreateHeader(header)
if err != nil {
return err
}
input, err := r.openFile(item.Location)
if err != nil {
return err
}
_, err = io.Copy(imageOutput{ctx, output}, input)
closeErr := input.Close()
if err != nil {
return err
}
if closeErr != nil {
return closeErr
}
}
return archive.Close()
}