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// 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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"encoding/binary"
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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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"unicode/utf16"
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"unicode/utf8"
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"github.com/xiaoqidun/pdfgo"
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)
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// image 转换图像样本，不将整页或其他对象栅格化
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func (p *pdfImporter) image(mark pdfgo.ImageMark) error {
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source := mark.Image
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filter, err := p.reader.Resolve(source.Stream.Dictionary["Filter"])
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if err != nil {
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return err
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}
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jpegOriginal := filter == pdfgo.Name("DCTDecode") && len(source.Decode) == 0 && !source.ImageMask && source.ColorSpace != pdfgo.Name("DeviceCMYK")
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if source.Mask != nil || source.SoftMask != nil {
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return &pdfgo.UnsupportedError{Feature: "image mask conversion"}
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}
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if !source.ImageMask && source.ColorSpace != pdfgo.Name("DeviceRGB") && source.ColorSpace != pdfgo.Name("DeviceGray") && source.ColorSpace != pdfgo.Name("DeviceCMYK") {
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return &pdfgo.UnsupportedError{Feature: "image color management"}
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}
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if source.Stream.Dictionary["Intent"] != nil || source.Stream.Dictionary["SMaskInData"] != nil {
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return &pdfgo.UnsupportedError{Feature: "image rendering attributes"}
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}
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decoded, err := source.DecodeSamples()
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if err != nil {
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return err
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}
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if len(source.Decode) > 0 {
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components := 1
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if source.ColorSpace == pdfgo.Name("DeviceRGB") {
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components = 3
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} else if source.ColorSpace == pdfgo.Name("DeviceCMYK") {
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components = 4
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}
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if len(source.Decode) != components*2 {
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return fmt.Errorf("invalid PDF image field %q", "Decode")
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}
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ranges := make([]float64, len(source.Decode))
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for n, v := range source.Decode {
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switch v := v.(type) {
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case pdfgo.Integer:
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ranges[n] = float64(v)
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case pdfgo.Real:
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ranges[n] = float64(v)
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default:
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return fmt.Errorf("invalid PDF image field %q", "Decode")
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}
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}
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adjusted := image.NewNRGBA64(image.Rect(0, 0, source.Width, source.Height))
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for y := 0; y < source.Height; y++ {
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for x := 0; x < source.Width; x++ {
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if components == 4 {
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cmyk, ok := decoded.At(x, y).(color.CMYK)
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if !ok {
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return fmt.Errorf("invalid CMYK image samples")
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}
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values := []uint8{cmyk.C, cmyk.M, cmyk.Y, cmyk.K}
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for c := range values {
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value := ranges[2*c] + float64(values[c])/255*(ranges[2*c+1]-ranges[2*c])
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values[c] = uint8(math.Round(math.Max(0, math.Min(1, value)) * 255))
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}
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adjusted.Set(x, y, color.CMYK{C: values[0], M: values[1], Y: values[2], K: values[3]})
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continue
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}
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r, g, b, _ := decoded.At(x, y).RGBA()
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values := []uint32{r, g, b}
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for c := range values {
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index := c
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if components == 1 {
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index = 0
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}
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value := ranges[2*index] + float64(values[c])/65535*(ranges[2*index+1]-ranges[2*index])
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values[c] = uint32(math.Round(math.Max(0, math.Min(1, value)) * 65535))
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}
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adjusted.SetNRGBA64(x, y, color.NRGBA64{R: uint16(values[0]), G: uint16(values[1]), B: uint16(values[2]), A: 65535})
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}
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}
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decoded = adjusted
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}
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if source.ImageMask {
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if mark.Style.Fill.CMYK != nil {
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return &pdfgo.UnsupportedError{Feature: "CMYK stencil image"}
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}
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stencil := image.NewNRGBA64(image.Rect(0, 0, source.Width, source.Height))
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fill := mark.Style.Fill.RGB
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for y := 0; y < source.Height; y++ {
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for x := 0; x < source.Width; x++ {
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gray, _, _, _ := decoded.At(x, y).RGBA()
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stencil.SetNRGBA64(x, y, color.NRGBA64{
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R: uint16(math.Round(fill[0] * 65535)),
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G: uint16(math.Round(fill[1] * 65535)),
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B: uint16(math.Round(fill[2] * 65535)),
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A: uint16(65535 - gray),
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})
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}
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}
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decoded = stencil
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}
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var encoded bytes.Buffer
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if jpegOriginal {
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encoded.Write(source.Stream.Data)
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} else {
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if err := png.Encode(&encoded, decoded); err != nil {
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return err
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}
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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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m := p.matrix.Mul(mark.Matrix).Mul(pdfgo.Matrix{1, 0, 0, -1, 0, 1})
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box := pdfBounds([]pdfgo.Point{m.Apply(pdfgo.Point{}), m.Apply(pdfgo.Point{X: 1}), m.Apply(pdfgo.Point{Y: 1}), m.Apply(pdfgo.Point{X: 1, Y: 1})})
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alpha := int(math.Round(mark.Style.Fill.Alpha * 255))
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object := ImageObject{Boundary: pdfBoundary(box), ResourceID: id, CTM: pdfNumbers(m[0], m[1], m[2], m[3], m[4]-box.X, m[5]-box.Y), Alpha: &alpha, Clips: p.clips(mark.Style.Clips, box)}
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p.objects = append(p.objects, GraphicObject{Type: "ImageObject", ImageObject: object})
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p.report.ImageObjects++
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return nil
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}
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// text 保留原字体、字形编号与逐字基线，不重新塑形
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func (p *pdfImporter) text(mark pdfgo.TextMark) error {
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font := mark.Font
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if len(font.Program) == 0 {
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return &pdfgo.UnsupportedError{Feature: "text without embedded font"}
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}
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if font.ProgramType != "FontFile2" && font.ProgramType != "OpenType" {
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return &pdfgo.UnsupportedError{Feature: "font program " + string(font.ProgramType)}
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}
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id := p.fontIDs[font]
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if id == "" {
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var err error
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program, err := pdfFontProgram(font)
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if err != nil {
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return err
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}
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id, err = p.editor.AddFont(FontFile{Name: font.Name + ".ttf", Data: program}, 0)
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if err != nil {
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return err
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}
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p.fontIDs[font] = id
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}
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metrics := p.fontMetrics[id]
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if metrics == nil {
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if p.editor.backends.Fonts == nil {
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return fmt.Errorf("PDF font backend unavailable")
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}
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var err error
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metrics, err = p.editor.backends.Fonts.OpenFont(p.editor.fonts[id].Data)
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if err != nil {
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return err
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}
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p.fontMetrics[id] = metrics
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}
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outline, ok := metrics.(FontOutlines)
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if !ok {
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return fmt.Errorf("PDF font backend does not provide glyph outlines")
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}
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const unit = 25.4 / 72
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m := p.matrix.Mul(mark.Matrix).Mul(pdfgo.Matrix{1 / unit, 0, 0, -1 / unit, 0, 0})
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var points []pdfgo.Point
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object := TextObject{Font: id, Size: mark.Size * unit, HScale: mark.HorizontalScale}
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position := 0
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for n, glyph := range mark.Glyphs {
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gid := glyph.ID
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if !glyph.HasID {
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if utf8.RuneCountInString(glyph.Text) != 1 {
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return &pdfgo.UnsupportedError{Feature: "simple font glyph ligature mapping"}
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}
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char, _ := utf8.DecodeRuneInString(glyph.Text)
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gid = metrics.GlyphIndex(char)
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if gid == 0 && char != 0 {
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return fmt.Errorf("missing PDF glyph for %U", char)
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}
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}
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if gid >= metrics.NumGlyphs() {
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return fmt.Errorf("PDF glyph index outside embedded font")
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}
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origin := mark.Positions[n]
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object.TextCode = append(object.TextCode, TextCode{X: pdfNumbers(origin.X * unit), Y: pdfNumbers(-origin.Y * unit), Value: glyph.Text})
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object.CGTransform = append(object.CGTransform, CGTransform{CodePosition: position, CodeCount: utf8.RuneCountInString(glyph.Text), GlyphCount: 1, Glyphs: strconv.Itoa(int(gid))})
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position += utf8.RuneCountInString(glyph.Text)
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path, err := outline.GlyphOutline(gid, object.Size)
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if err != nil {
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return err
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}
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bounds, err := path.Bounds()
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if err != nil {
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return err
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}
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for _, point := range []pdfgo.Point{{X: bounds.X, Y: bounds.Y}, {X: bounds.X + bounds.W, Y: bounds.Y}, {X: bounds.X, Y: bounds.Y + bounds.H}, {X: bounds.X + bounds.W, Y: bounds.Y + bounds.H}} {
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points = append(points, m.Apply(pdfgo.Point{X: origin.X*unit + point.X*mark.HorizontalScale, Y: -origin.Y*unit + point.Y}))
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}
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}
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box := pdfBounds(points)
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fill, stroke, visible := mark.Mode == 0 || mark.Mode == 2, mark.Mode == 1 || mark.Mode == 2, mark.Mode != 3
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if stroke {
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margin := mark.Style.LineWidth * unit * math.Hypot(m[0], m[1]) / 2 * math.Max(1, mark.Style.MiterLimit)
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box = Box{box.X - margin, box.Y - margin, box.W + 2*margin, box.H + 2*margin}
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color := StrokeColor(*p.color(mark.Style.Stroke))
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object.StrokeColor = &color
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object.LineWidth = mark.Style.LineWidth * unit
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object.Join = []string{"Miter", "Round", "Bevel"}[mark.Style.Join]
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object.MiterLimit = mark.Style.MiterLimit
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if len(mark.Style.Dash) > 0 {
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return &pdfgo.UnsupportedError{Feature: "dashed text stroke"}
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}
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}
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object.Boundary = pdfBoundary(box)
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object.CTM = pdfNumbers(m[0], m[1], m[2], m[3], m[4]-box.X, m[5]-box.Y)
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object.Fill = &fill
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object.Stroke = &stroke
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object.Visible = &visible
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object.FillColor = p.color(mark.Style.Fill)
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object.Clips = p.clips(mark.Style.Clips, box)
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p.objects = append(p.objects, GraphicObject{Type: "TextObject", TextObject: object})
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p.report.TextObjects++
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return nil
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}
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// pdfFontProgram 为PDF子集字体补齐封装表，不改动字形轮廓、编号或原始度量
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func pdfFontProgram(source *pdfgo.Font) ([]byte, error) {
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tables, err := fontFileTables(source.Program, 0)
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if err != nil {
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return nil, err
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}
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if len(tables["head"]) < 54 || len(tables["maxp"]) < 6 || len(tables["hhea"]) < 36 || len(tables["hmtx"]) == 0 {
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return nil, fmt.Errorf("embedded PDF font lacks required metrics")
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}
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count := binary.BigEndian.Uint16(tables["maxp"][4:6])
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if count == 0 {
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return nil, fmt.Errorf("embedded PDF font has no glyphs")
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}
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changed := false
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if len(tables["cmap"]) == 0 {
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mapping := map[rune]uint16{}
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for code := range source.Unicode {
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glyphs, err := source.Decode([]byte(code))
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if err != nil {
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return nil, err
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}
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if len(glyphs) != 1 || !glyphs[0].HasID {
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return nil, &pdfgo.UnsupportedError{Feature: "font without explicit glyph mapping"}
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}
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glyph := glyphs[0]
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if utf8.RuneCountInString(glyph.Text) == 1 {
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char, _ := utf8.DecodeRuneInString(glyph.Text)
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if _, exists := mapping[char]; !exists {
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mapping[char] = glyph.ID
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}
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}
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}
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addPackedGlyphMapping(mapping, count)
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tables["cmap"] = buildCmapTable(count, mapping)
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changed = true
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}
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if len(fontNamesFromTable(tables["name"])) == 0 {
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name := utf16.Encode([]rune(source.Name))
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if len(name) == 0 || len(name) > 32767 {
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return nil, fmt.Errorf("PDF font name missing or excessive")
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}
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data := make([]byte, 42+len(name)*2)
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binary.BigEndian.PutUint16(data[2:], 3)
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binary.BigEndian.PutUint16(data[4:], 42)
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for n, id := range []uint16{1, 4, 6} {
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record := data[6+n*12:]
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binary.BigEndian.PutUint16(record, 3)
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binary.BigEndian.PutUint16(record[2:], 1)
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binary.BigEndian.PutUint16(record[4:], 0x409)
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binary.BigEndian.PutUint16(record[6:], id)
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binary.BigEndian.PutUint16(record[8:], uint16(len(name)*2))
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}
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for n, v := range name {
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binary.BigEndian.PutUint16(data[42+n*2:], v)
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}
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tables["name"] = data
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changed = true
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}
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if len(tables["post"]) == 0 {
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tables["post"] = buildPostTable()
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changed = true
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}
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if len(tables["OS/2"]) == 0 {
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hhea := tables["hhea"]
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tables["OS/2"] = buildOS2TableWithMetrics(int16(binary.BigEndian.Uint16(hhea[4:6])), int16(binary.BigEndian.Uint16(hhea[6:8])))
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changed = true
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}
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if !changed {
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return source.Program, nil
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}
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return serializeOTF(tables)
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}
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