mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 17:27:08 +08:00
388 lines
14 KiB
Go
388 lines
14 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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"image/color"
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"image/png"
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"math"
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"strconv"
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"strings"
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"time"
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"github.com/xiaoqidun/pdfgo"
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)
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// stampAnnotation 将PDF印章外观转换为OFD注解
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// 入参: ctx取消上下文, page PDF页面, annotation PDF印章
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// 返回: error 外观或转换错误
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func (p *pdfImporter) stampAnnotation(ctx context.Context, page *pdfgo.Page, annotation pdfgo.Annotation) error {
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flags := int64(0)
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if value := annotation.Dictionary["F"]; value != nil {
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resolved, err := p.reader.Resolve(value)
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if err != nil {
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return err
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}
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number, ok := resolved.(pdfgo.Integer)
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if !ok {
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return fmt.Errorf("invalid PDF annotation flags")
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}
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flags = int64(number)
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}
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box := pdfBounds([]pdfgo.Point{
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p.matrix.Apply(pdfgo.Point{X: annotation.Rect.XMin, Y: annotation.Rect.YMin}),
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p.matrix.Apply(pdfgo.Point{X: annotation.Rect.XMax, Y: annotation.Rect.YMin}),
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p.matrix.Apply(pdfgo.Point{X: annotation.Rect.XMax, Y: annotation.Rect.YMax}),
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p.matrix.Apply(pdfgo.Point{X: annotation.Rect.XMin, Y: annotation.Rect.YMax}),
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})
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stamp := *p
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stamp.matrix = (pdfgo.Matrix{1, 0, 0, 1, -box.X, -box.Y}).Mul(p.matrix)
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stamp.objects = nil
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stamp.pendingPath = nil
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stamp.report = PDFImportReport{}
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var darkenImages []pdfgo.ImageMark
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visitor := pdfgo.Visitor{
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Path: func(mark pdfgo.PathMark) error {
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if mark.Style.BlendMode == "Darken" {
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return &pdfgo.UnsupportedError{Feature: "darken stamp path"}
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}
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return stamp.path(mark)
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},
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Text: func(mark pdfgo.TextMark) error {
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if mark.Style.BlendMode == "Darken" {
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return &pdfgo.UnsupportedError{Feature: "darken stamp text"}
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}
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if err := stamp.text(mark); err != nil {
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return fmt.Errorf("stamp text: %w", err)
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}
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return nil
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},
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Image: func(mark pdfgo.ImageMark) error {
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if mark.Style.BlendMode == "Darken" {
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darkenImages = append(darkenImages, mark)
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return nil
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}
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return stamp.image(mark)
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},
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}
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visitor.Group = func(group pdfgo.GroupMark, walk func(pdfgo.Visitor) error) error {
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return stamp.group(group, walk, visitor)
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}
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if err := p.reader.WalkAnnotationAppearance(ctx, page, annotation, visitor); err != nil {
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return err
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}
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if err := stamp.flushPath(); err != nil {
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return err
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}
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if len(darkenImages) != 0 {
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if len(darkenImages) != 1 || len(stamp.objects) != 0 {
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return &pdfgo.UnsupportedError{Feature: "mixed darken stamp appearance"}
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}
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if err := p.darkenStampAppearance(page, box, darkenImages[0], &stamp); err != nil {
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return err
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}
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p.report.Warnings = append(p.report.Warnings, pdfgo.Diagnostic{Page: p.page + 1, Message: "PDF darken stamp appearance flattened over page content"})
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}
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converted := Annotation{Type: "Stamp", Appearance: Appearance{Boundary: pdfBoundary(box), Objects: stamp.objects}}
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if flags&(1|2|32) != 0 {
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visible := false
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converted.Visible = &visible
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}
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converted.NoZoom = flags&8 != 0
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converted.NoRotate = flags&16 != 0
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if value := annotation.Dictionary["T"]; value != nil {
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resolved, err := p.reader.Resolve(value)
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if err != nil {
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return err
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}
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creator, ok := resolved.(pdfgo.String)
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if !ok {
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return fmt.Errorf("invalid PDF stamp creator")
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}
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converted.Creator, err = pdfgo.DecodeTextString(creator)
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if err != nil {
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return err
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}
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}
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if value := annotation.Dictionary["M"]; value != nil {
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resolved, err := p.reader.Resolve(value)
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if err != nil {
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return err
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}
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encoded, ok := resolved.(pdfgo.String)
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if !ok {
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return fmt.Errorf("invalid PDF stamp modification date")
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}
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date, err := pdfgo.DecodeTextString(encoded)
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if err != nil {
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return err
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}
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date = strings.TrimPrefix(date, "D:")
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if len(date) < 4 {
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return fmt.Errorf("invalid PDF stamp modification date")
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}
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year, err := strconv.Atoi(date[:4])
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if err != nil {
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return fmt.Errorf("invalid PDF stamp modification date: %w", err)
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}
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month, day := 1, 1
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if len(date) >= 6 {
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month, err = strconv.Atoi(date[4:6])
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if err != nil {
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return fmt.Errorf("invalid PDF stamp modification month: %w", err)
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}
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}
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if len(date) >= 8 {
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day, err = strconv.Atoi(date[6:8])
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if err != nil {
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return fmt.Errorf("invalid PDF stamp modification day: %w", err)
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}
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}
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parsed := time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.UTC)
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if parsed.Year() != year || int(parsed.Month()) != month || parsed.Day() != day {
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return fmt.Errorf("invalid PDF stamp modification date")
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}
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converted.LastModDate = parsed.Format("2006-01-02")
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if len(date) > 8 {
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p.report.Warnings = append(p.report.Warnings, pdfgo.Diagnostic{Page: p.page + 1, Message: "PDF stamp modification time cannot fit OFD annotation date"})
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}
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}
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if _, err := p.editor.AddAnnotation(p.page, converted); err != nil {
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return fmt.Errorf("stamp annotation: %w", err)
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}
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p.report.TextObjects += stamp.report.TextObjects
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p.report.PathObjects += stamp.report.PathObjects
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p.report.ImageObjects += stamp.report.ImageObjects
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if flags&64 != 0 {
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p.report.Warnings = append(p.report.Warnings, pdfgo.Diagnostic{Page: p.page + 1, Message: "PDF stamp read-only flag not transferred"})
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}
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return nil
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}
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// darkenStampAppearance 按PDF的Darken公式合成印章范围
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// 入参: page PDF页面, box印章范围, mark图像, stamp局部转换器
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// 返回: error 转换错误
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func (p *pdfImporter) darkenStampAppearance(page *pdfgo.Page, box Box, mark pdfgo.ImageMark, stamp *pdfImporter) error {
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if err := p.commitObjects(); err != nil {
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return err
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}
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base, err := renderImportedPage(p.editor, p.page, false)
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if err != nil {
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return err
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}
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_, width, height := pdfPageMatrix(page)
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appearance := NewEditor()
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appearance.SetRenderBackends(p.editor.backends)
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if _, err := appearance.AddPage(width, height); err != nil {
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return err
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}
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imageImporter := pdfImporter{reader: p.reader, editor: appearance, matrix: p.matrix, pageBox: page.CropBox}
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mark.Style.BlendMode = "Normal"
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if err := imageImporter.image(mark); err != nil {
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return err
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}
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if _, err := appearance.CopyObjects(0, imageImporter.objects, 0, 0); err != nil {
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return err
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}
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overlay, err := renderImportedPage(appearance, 0, true)
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if err != nil {
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return err
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}
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if base.Bounds() != overlay.Bounds() {
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return fmt.Errorf("stamp appearance page size mismatch")
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}
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const dpi = 300.0
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pixelsPerMM := dpi / 25.4
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region := image.Rect(int(math.Floor(box.X*pixelsPerMM)), int(math.Floor(box.Y*pixelsPerMM)), int(math.Ceil((box.X+box.W)*pixelsPerMM)), int(math.Ceil((box.Y+box.H)*pixelsPerMM))).Intersect(base.Bounds())
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if region.Empty() {
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return fmt.Errorf("stamp appearance outside page")
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}
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composite := image.NewRGBA(image.Rect(0, 0, region.Dx(), region.Dy()))
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for y := region.Min.Y; y < region.Max.Y; y++ {
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for x := region.Min.X; x < region.Max.X; x++ {
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background := color.NRGBAModel.Convert(base.At(x, y)).(color.NRGBA)
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foreground := color.NRGBAModel.Convert(overlay.At(x, y)).(color.NRGBA)
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alpha := float64(foreground.A) / 255
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blend := func(back, front uint8) uint8 {
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return uint8(math.Round((1-alpha)*float64(back) + alpha*math.Min(float64(back), float64(front))))
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}
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composite.SetRGBA(x-region.Min.X, y-region.Min.Y, color.RGBA{R: blend(background.R, foreground.R), G: blend(background.G, foreground.G), B: blend(background.B, foreground.B), A: 255})
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}
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}
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var encoded bytes.Buffer
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if err := png.Encode(&encoded, composite); err != nil {
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return err
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}
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id, err := p.editor.AddImage(encoded.Bytes())
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if err != nil {
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return err
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}
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regionBox := Box{X: float64(region.Min.X)/pixelsPerMM - box.X, Y: float64(region.Min.Y)/pixelsPerMM - box.Y, W: float64(region.Dx()) / pixelsPerMM, H: float64(region.Dy()) / pixelsPerMM}
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stamp.objects = append(stamp.objects, GraphicObject{Type: "ImageObject", ImageObject: ImageObject{Boundary: pdfBoundary(regionBox), ResourceID: id}})
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stamp.report.ImageObjects++
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return nil
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}
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// signatureWidget 转换可见签名外观，不将PDF签名误写成OFD签名
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// 入参: ctx 取消上下文, page PDF页面, annotation 签名控件
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// 返回: error 外观或转换错误
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func (p *pdfImporter) signatureWidget(ctx context.Context, page *pdfgo.Page, annotation pdfgo.Annotation) error {
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if annotation.Dictionary["FT"] != pdfgo.Name("Sig") || annotation.Dictionary["V"] == nil {
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return &pdfgo.UnsupportedError{Feature: "non-signature widget"}
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}
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flags := int64(0)
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if value := annotation.Dictionary["F"]; value != nil {
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resolved, err := p.reader.Resolve(value)
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if err != nil {
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return err
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}
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number, ok := resolved.(pdfgo.Integer)
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if !ok {
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return fmt.Errorf("invalid PDF annotation flags")
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}
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flags = int64(number)
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}
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const invisibleFlags = 1 | 2 | 32
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if flags&invisibleFlags != 0 {
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p.report.Warnings = append(p.report.Warnings, pdfgo.Diagnostic{Page: p.page + 1, Message: "hidden PDF signature not transferred"})
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return nil
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}
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var images []pdfgo.ImageMark
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visitor := pdfgo.Visitor{
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Path: func(pdfgo.PathMark) error { return &pdfgo.UnsupportedError{Feature: "signature appearance path"} },
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Text: func(pdfgo.TextMark) error { return &pdfgo.UnsupportedError{Feature: "signature appearance text"} },
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Image: func(mark pdfgo.ImageMark) error {
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images = append(images, mark)
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return nil
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},
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}
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if err := p.reader.WalkAnnotationAppearance(ctx, page, annotation, visitor); err != nil {
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return err
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}
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if len(images) != 1 {
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return &pdfgo.UnsupportedError{Feature: "signature appearance composition"}
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}
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mark := images[0]
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message := "PDF signature appearance imported; digital signature not transferred"
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if mark.Style.BlendMode == "Multiply" {
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if err := p.multiplySignatureAppearance(page, annotation, mark); err != nil {
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return err
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}
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message = "PDF signature appearance flattened over page content; digital signature not transferred"
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} else if mark.Style.BlendMode == "" || mark.Style.BlendMode == "Normal" || mark.Style.BlendMode == "Compatible" {
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if err := p.image(mark); err != nil {
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return err
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}
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} else {
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return &pdfgo.UnsupportedError{Feature: "signature appearance blend mode"}
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}
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p.report.Warnings = append(p.report.Warnings, pdfgo.Diagnostic{Page: p.page + 1, Message: message})
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return nil
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}
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// multiplySignatureAppearance 合成签名覆盖区域，正文及其他页面对象保持独立
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// 入参: page PDF页面, annotation 签名控件, mark 印章图像
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// 返回: error 图像或渲染错误
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func (p *pdfImporter) multiplySignatureAppearance(page *pdfgo.Page, annotation pdfgo.Annotation, mark pdfgo.ImageMark) error {
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if err := p.commitObjects(); err != nil {
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return err
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}
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base, err := renderImportedPage(p.editor, p.page, false)
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if err != nil {
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return err
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}
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_, width, height := pdfPageMatrix(page)
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appearance := NewEditor()
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appearance.SetRenderBackends(p.editor.backends)
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if _, err := appearance.AddPage(width, height); err != nil {
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return err
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}
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stamp := pdfImporter{reader: p.reader, editor: appearance, matrix: p.matrix, pageBox: page.CropBox}
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mark.Style.BlendMode = "Normal"
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if err := stamp.image(mark); err != nil {
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return err
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}
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if _, err := appearance.CopyObjects(0, stamp.objects, 0, 0); err != nil {
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return err
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}
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overlay, err := renderImportedPage(appearance, 0, false)
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if err != nil {
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return err
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}
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if base.Bounds() != overlay.Bounds() {
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return fmt.Errorf("signature appearance page size mismatch")
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}
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annotationBox := annotation.Rect
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box := pdfBounds([]pdfgo.Point{
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p.matrix.Apply(pdfgo.Point{X: annotationBox.XMin, Y: annotationBox.YMin}),
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p.matrix.Apply(pdfgo.Point{X: annotationBox.XMax, Y: annotationBox.YMin}),
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p.matrix.Apply(pdfgo.Point{X: annotationBox.XMax, Y: annotationBox.YMax}),
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p.matrix.Apply(pdfgo.Point{X: annotationBox.XMin, Y: annotationBox.YMax}),
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})
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const dpi = 300.0
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pixelsPerMM := dpi / 25.4
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region := image.Rect(int(math.Floor(box.X*pixelsPerMM)), int(math.Floor(box.Y*pixelsPerMM)), int(math.Ceil((box.X+box.W)*pixelsPerMM)), int(math.Ceil((box.Y+box.H)*pixelsPerMM))).Intersect(base.Bounds())
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if region.Empty() {
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return fmt.Errorf("signature appearance outside page")
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}
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composite := image.NewRGBA(image.Rect(0, 0, region.Dx(), region.Dy()))
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for y := region.Min.Y; y < region.Max.Y; y++ {
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for x := region.Min.X; x < region.Max.X; x++ {
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background := color.RGBAModel.Convert(base.At(x, y)).(color.RGBA)
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foreground := color.RGBAModel.Convert(overlay.At(x, y)).(color.RGBA)
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composite.SetRGBA(x-region.Min.X, y-region.Min.Y, color.RGBA{
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R: uint8((int(background.R)*int(foreground.R) + 127) / 255),
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G: uint8((int(background.G)*int(foreground.G) + 127) / 255),
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B: uint8((int(background.B)*int(foreground.B) + 127) / 255),
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A: 255,
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})
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}
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}
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var encoded bytes.Buffer
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if err := png.Encode(&encoded, composite); err != nil {
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return err
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}
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id, err := p.editor.AddImage(encoded.Bytes())
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if err != nil {
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return err
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}
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regionBox := Box{X: float64(region.Min.X) / pixelsPerMM, Y: float64(region.Min.Y) / pixelsPerMM, W: float64(region.Dx()) / pixelsPerMM, H: float64(region.Dy()) / pixelsPerMM}
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p.objects = append(p.objects, GraphicObject{Type: "ImageObject", ImageObject: ImageObject{Boundary: pdfBoundary(regionBox), ResourceID: id}})
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p.report.ImageObjects++
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return nil
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}
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// renderImportedPage 在固定印刷分辨率绘制待合成页面
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// 入参: editor 编辑文档, page 页序号, transparent 是否保留透明背景
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// 返回: image.Image 页面像素, error 渲染错误
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func renderImportedPage(editor *Editor, page int, transparent bool) (image.Image, error) {
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reader, err := editor.Reader()
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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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content, err := reader.PageContentByIndex(page)
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if err != nil {
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return nil, err
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}
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renderer := NewRenderer(reader, WithDPI(300), WithRenderBackends(editor.backends), WithAnnotations(!transparent))
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renderer.TransparentBackground = transparent
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return renderer.RenderToImage(content)
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}
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