feat(文字图像): 修复文字定位及图像导出

go.mod

@@ -10,7 +10,7 @@ require (
 	github.com/tdewolff/canvas v0.0.0-20260923214215-09804640d00c
 	github.com/tdewolff/font v0.0.0-20260913163313-54f98bb59ee6
 	github.com/xiaoqidun/jbig2 v1.1.1
-	github.com/xiaoqidun/pdfgo v0.0.0-20261003024624-bf2ee2f33c58
+	github.com/xiaoqidun/pdfgo v0.0.0-20261003042717-ffb073d5634d
 	golang.org/x/crypto v0.57.0
 	golang.org/x/image v0.46.0
 	golang.org/x/text v0.42.0

go.sum

@@ -62,8 +62,8 @@ github.com/tdewolff/test v1.0.12 h1:7F21DqIajswxuche0geHdrUZRCWE4oko4b7bcmkkrxk=
 github.com/tdewolff/test v1.0.12/go.mod h1:XPuWBzvdUzhCuxWO1ojpXsyzsA5bFoS3tO/Q3kFuTG8=
 github.com/xiaoqidun/jbig2 v1.1.1 h1:SjliS9ZO0e9HX5oYUfBuXrfFsXhWricrSz+XY4zORDI=
 github.com/xiaoqidun/jbig2 v1.1.1/go.mod h1:8QonVWtENmh2kc6l+leqeGl7psb79DWlHDkCpdChjfQ=
-github.com/xiaoqidun/pdfgo v0.0.0-20261003024624-bf2ee2f33c58 h1:n2RFxdeo5fmtvgkRKeMSgJHqmVEGMoS45SppUk4laaE=
-github.com/xiaoqidun/pdfgo v0.0.0-20261003024624-bf2ee2f33c58/go.mod h1:4Pf0JO0BEf1uzRY+uZjlMjN/OPn3PYa0YMi6cqPPTLQ=
+github.com/xiaoqidun/pdfgo v0.0.0-20261003042717-ffb073d5634d h1:WiG6LgYU1hZBAELi72qP6UnCyA8cPe7Ap6nto0ofGnA=
+github.com/xiaoqidun/pdfgo v0.0.0-20261003042717-ffb073d5634d/go.mod h1:4Pf0JO0BEf1uzRY+uZjlMjN/OPn3PYa0YMi6cqPPTLQ=
 github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
 github.com/xyproto/randomstring v1.0.5/go.mod h1:rgmS5DeNXLivK7YprL0pY+lTuhNQW3iGxZ18UQApw/E=
 github.com/yuin/goldmark v1.8.5 h1:r6N5afV5qj/5S4UTch8agZHJ8UxNCMwX7WjkkJam2NA=

ofdgo_renderer_image_canvas.go

@@ -108,11 +108,14 @@ func (r *Renderer) renderImage(ctx *canvas.Context, obj ImageObject, pageH float
 		return
 	}
 	m = m.Scale(imgW/float64(img.Bounds().Dx()), imgH/float64(img.Bounds().Dy()))
-	img, pad := imageWithTransparentEdge(img)
-	if pad > 0 {
-		p := float64(pad)
-		m[0][2] -= m[0][0]*p + m[0][1]*p
-		m[1][2] -= m[1][0]*p + m[1][1]*p
+	if _, pdf := ctx.Renderer.(*pdfRenderer); !pdf {
+		var pad int
+		img, pad = imageWithTransparentEdge(img)
+		if pad > 0 {
+			p := float64(pad)
+			m[0][2] -= m[0][0]*p + m[0][1]*p
+			m[1][2] -= m[1][0]*p + m[1][1]*p
+		}
 	}
 	ctx.RenderImage(r.canvasEncodedImage(img), ctx.CoordSystemView().Mul(ctx.View()).Mul(m))
 	if compiled && imageClip != nil && compiler.err == nil {

ofdgo_renderer_output_canvas.go

@@ -18,6 +18,7 @@ import (
 	"bufio"
 	"bytes"
 	"fmt"
+	"image"
 	"io"
 
 	"github.com/tdewolff/canvas"
@@ -126,7 +127,7 @@ func (CanvasBackend) RenderPDF(r *Renderer, pages []RenderDocumentPage, writer i
 	}
 	start := buf.Len()
 	p := pdf.New(buf, pages[0].Box.W, pages[0].Box.H, nil)
-	renderer := &pdfRenderer{PDF: p, glyphPaths: make(map[*canvas.Path]*canvas.Path)}
+	renderer := &pdfRenderer{PDF: p, glyphPaths: make(map[*canvas.Path]*canvas.Path), images: make([][]image.Image, 1)}
 	var info DocInfo
 	if docInfo, err := r.Reader.DocInfo(); err == nil {
 		info = *docInfo
@@ -135,6 +136,7 @@ func (CanvasBackend) RenderPDF(r *Renderer, pages []RenderDocumentPage, writer i
 	for i, page := range pages {
 		if i > 0 {
 			p.NewPage(page.Box.W, page.Box.H)
+			renderer.images = append(renderer.images, nil)
 		}
 		navigation.apply(p, i)
 		if err := r.renderCanvasPageToContext(canvas.NewContext(renderer), page.Content, !r.TransparentBackground); err != nil {
@@ -154,6 +156,16 @@ func (CanvasBackend) RenderPDF(r *Renderer, pages []RenderDocumentPage, writer i
 		return err
 	}
 	data := replacePDFProducer(buf.Bytes()[start:])
+	data, err = renderer.preserveImages(r.outputContext(), data)
+	if err != nil {
+		buf.Truncate(start)
+		return err
+	}
+	if direct && renderer.exactImages {
+		buf.Truncate(start)
+		_, err = buf.Write(data)
+		return err
+	}
 	if r.Compression.Mode != CompressionUnchanged {
 		reader, err := pdfgo.NewReader(bytes.NewReader(data), int64(len(data)))
 		if err != nil {
@@ -171,7 +183,10 @@ func (CanvasBackend) RenderPDF(r *Renderer, pages []RenderDocumentPage, writer i
 	if direct {
 		return nil
 	}
-	_, err = writer.Write(data)
+	n, err := writer.Write(data)
+	if err == nil && n != len(data) {
+		err = io.ErrShortWrite
+	}
 	return err
 }
 

ofdgo_renderer_pdf_canvas.go

@@ -17,15 +17,19 @@ package ofdgo
 import (
 	"fmt"
 	"image"
+	"image/color"
 
 	"github.com/tdewolff/canvas"
+	cimage "github.com/tdewolff/canvas/image"
 	"github.com/tdewolff/canvas/renderers/pdf"
 )
 
 // pdfRenderer PDF渲染器
 type pdfRenderer struct {
 	*pdf.PDF
-	glyphPaths map[*canvas.Path]*canvas.Path
+	glyphPaths  map[*canvas.Path]*canvas.Path
+	images      [][]image.Image
+	exactImages bool
 }
 
 // pdfNavigation PDF导航信息
@@ -58,6 +62,27 @@ type pdfOutline struct {
 // RenderImage 在图像局部保存状态前同步不透明画笔，避免恢复后的透明度与后端缓存不一致
 // 入参: img 图像, matrix 图像变换
 func (r *pdfRenderer) RenderImage(img image.Image, matrix canvas.Matrix) {
+	if len(r.images) != 0 {
+		var original image.Image
+		opaque := false
+		if source, ok := img.(interface{ Opaque() bool }); ok {
+			opaque = source.Opaque()
+		}
+		switch img.ColorModel() {
+		case color.GrayModel, color.CMYKModel:
+		case color.RGBAModel, color.NRGBAModel, color.AlphaModel:
+			if !opaque {
+				original = img
+			}
+		default:
+			if source, ok := img.(*cimage.Image); !ok || source.Mimetype != "image/jpeg" || source.Mask != nil {
+				original = img
+			}
+		}
+		r.exactImages = r.exactImages || original != nil
+		last := len(r.images) - 1
+		r.images[last] = append(r.images[last], original)
+	}
 	style := canvas.DefaultStyle
 	style.Fill = canvas.Paint{Color: canvas.White}
 	style.Stroke = canvas.Paint{Color: canvas.Black}

ofdgo_renderer_pdf_images.go

@@ -0,0 +1,106 @@
+// 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 (
+	"bytes"
+	"context"
+	"fmt"
+	"image"
+
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// 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
+// 入参: ctx 取消上下文, data 后端PDF数据
+// 返回: []byte 保留图像精度的PDF数据, error 资源或写入错误
+func (r *pdfRenderer) preserveImages(ctx context.Context, data []byte) ([]byte, error) {
+	if !r.exactImages {
+		return data, nil
+	}
+	reader, err := pdfgo.NewReader(bytes.NewReader(data), int64(len(data)))
+	if err != nil {
+		return nil, err
+	}
+	defer reader.Close()
+	images := make(map[pdfgo.Reference]image.Image)
+	pages := 0
+	err = reader.WalkPages(ctx, func(index int, page *pdfgo.Page) error {
+		if index >= len(r.images) {
+			return fmt.Errorf("unexpected PDF output page")
+		}
+		pages++
+		value, err := reader.Resolve(page.Resources["XObject"])
+		if err != nil {
+			return err
+		}
+		resources, _ := value.(pdfgo.Dictionary)
+		var content bytes.Buffer
+		if _, err := page.WriteContent(ctx, &content); err != nil {
+			return err
+		}
+		position := 0
+		if err := pdfgo.WalkOperations(ctx, content.Bytes(), func(operation pdfgo.Operation) error {
+			if operation.Operator != "Do" {
+				return nil
+			}
+			if len(operation.Operands) != 1 || position >= len(r.images[index]) {
+				return fmt.Errorf("unexpected PDF output image")
+			}
+			name, ok := operation.Operands[0].(pdfgo.Name)
+			if !ok {
+				return fmt.Errorf("invalid PDF output image name")
+			}
+			ref, ok := resources[name].(pdfgo.Reference)
+			if !ok {
+				return fmt.Errorf("invalid PDF output image reference")
+			}
+			original := r.images[index][position]
+			position++
+			if original == nil {
+				return nil
+			}
+			image, err := reader.ReadImage(ref)
+			if err != nil {
+				return err
+			}
+			if image.Width != original.Bounds().Dx() || image.Height != original.Bounds().Dy() {
+				return fmt.Errorf("PDF output image dimensions differ")
+			}
+			if previous := images[ref]; previous != nil && previous != original {
+				return fmt.Errorf("PDF output image reference conflicts")
+			}
+			images[ref] = original
+			return nil
+		}); err != nil {
+			return err
+		}
+		if position != len(r.images[index]) {
+			return fmt.Errorf("PDF output image missing")
+		}
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	if pages != len(r.images) {
+		return nil, fmt.Errorf("PDF output page missing")
+	}
+	var result bytes.Buffer
+	if _, err := reader.ReplaceImagesTo(ctx, &result, images); err != nil {
+		return nil, err
+	}
+	return result.Bytes(), nil
+}

ofdgo_renderer_text_canvas.go

@@ -18,6 +18,7 @@ import (
 	"strings"
 
 	"github.com/tdewolff/canvas"
+	"github.com/tdewolff/font"
 )
 
 const ptPerMM = 72.0 / 25.4
@@ -181,7 +182,7 @@ func (r *Renderer) renderText(ctx *canvas.Context, obj TextObject, pageH float64
 		ctx.Pop()
 		return
 	}
-	face := ff.Face(sizePt, fillPaint, fontStyle, canvas.FontNormal)
+	face := ff.Face(sizePt, fillPaint, fontStyle, canvas.FontNormal, font.NoHinting)
 	recoverBaseline := len(obj.TextCode) > 0 && obj.TextCode[0].Y == ""
 	var metrics canvas.FontMetrics
 	if textRun != nil || recoverBaseline {