feat(转换能力): 增强PDF转换，优化大文档编辑，并支持直接保存OFD

assets/webui/index.html

@@ -18,6 +18,7 @@
 			<div class="tool-group">
 				<button id="ofdButton" class="icon-button" type="button" title="打开" aria-label="打开" aria-keyshortcuts="Control+O Meta+O"><span class="open-icon" aria-hidden="true"></span></button>
 				<button id="newButton" class="icon-button" type="button" title="新建" aria-label="新建"><span class="new-icon" aria-hidden="true"></span></button>
+				<button id="saveButton" class="icon-button" type="button" title="保存" aria-label="保存" aria-keyshortcuts="Control+S Meta+S" disabled><span class="save-icon" aria-hidden="true"></span></button>
 				<button id="editButton" class="icon-button" type="button" title="编辑" aria-label="编辑" aria-pressed="false" disabled><span class="edit-icon" aria-hidden="true"></span></button>
 				<button id="togglePagesButton" class="icon-button" type="button" title="页面栏" aria-label="页面栏" aria-pressed="true">&#9776;</button>
 				<button id="toggleMetaButton" class="icon-button" type="button" title="信息栏" aria-label="信息栏" aria-pressed="true">&#9432;</button>
@@ -60,11 +61,10 @@
 			</div>
 		</header>
 		<div id="editorTools" class="editor-toolbar" role="toolbar" aria-label="编辑工具" hidden>
-			<div class="editor-group editor-file">
-				<button id="saveButton" class="button" type="button" title="另存为OFD" aria-label="另存为OFD" aria-keyshortcuts="Control+S Meta+S">保存</button>
+			<div class="editor-group editor-actions">
 				<button id="undoButton" class="button" type="button" disabled>撤销</button>
 				<button id="redoButton" class="button" type="button" disabled>重做</button>
-				<span>文件</span>
+				<span>操作</span>
 			</div>
 			<div class="editor-group editor-objects">
 				<button id="compositeBackButton" class="button" type="button" title="返回上层" hidden>返回</button>

assets/webui/ofdgo.css

@@ -111,11 +111,11 @@ a:focus-visible {
 	border-right: 1px solid var(--line);
 }
 
-.editor-file,
 .editor-image {
 	grid-template-columns: repeat(2, max-content);
 }
 
+.editor-actions,
 .editor-transform,
 .editor-erase {
 	grid-template-columns: max-content;
@@ -215,15 +215,6 @@ a:focus-visible {
 	grid-template-columns: repeat(2, 84px);
 }
 
-.editor-file #saveButton {
-	grid-row: 1 / 3;
-	height: 100%;
-}
-
-.editor-file #redoButton {
-	grid-column: 2;
-}
-
 .font-picker {
 	display: flex;
 	min-width: 0;
@@ -517,6 +508,13 @@ button:not(:disabled):hover {
 	transform: translate(-50%, -50%) rotate(90deg);
 }
 
+.save-icon {
+	width: 16px;
+	height: 16px;
+	background: currentColor;
+	mask: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='black' stroke-width='1.7' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M19 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h11l5 5v11a2 2 0 0 1-2 2Z'/%3E%3Cpath d='M17 21v-8H7v8M7 3v5h8'/%3E%3C/svg%3E") center / contain no-repeat;
+}
+
 .edit-icon {
 	position: relative;
 	width: 15px;

assets/webui/ofdgo.js

@@ -1333,7 +1333,8 @@ function handleKeyDown(event) {
 	}
 	const key = event.key;
 	const target = event.target;
-	if ((event.ctrlKey || event.metaKey) && !event.shiftKey && key.toLowerCase() === "s" && state.editorInfo) {
+	if ((event.ctrlKey || event.metaKey) && !event.shiftKey && key.toLowerCase() === "s" && state.doc
+		&& (state.editorInfo || state.ofdBytes)) {
 		event.preventDefault();
 		if (!document.body.hasAttribute("aria-busy") && !formDialogOpen()) exportFile(true, null, "ofd");
 		return;
@@ -1938,7 +1939,7 @@ async function toggleEditor() {
 		canvasEditor.clear();
 		setPan(false);
 		await openDocument({ doc, openSeq, skipAutoFonts: true, pageIndex, fitMode, scale,
-			keepPreview: true, previewAnchor: anchor });
+			keepPreview: true, preserveThumbnails: true, previewAnchor: anchor });
 	} catch (err) {
 		if (openSeq === state.openSeq) showError(err, false);
 	} finally {
@@ -3888,7 +3889,13 @@ async function openDocument(options = {}) {
 	}
 	const openSeq = options.openSeq || (state.openSeq += 1);
 	const previewPosition = options.previewScroll && state.pageWindow ? pageWindowAnchor(state.pageWindow) : null;
-	const previewIDs = options.keepPreview ? [...new Set([...state.visiblePages, ...state.visibleThumbnails])].map((index) => state.doc.pages[index].id) : [];
+	const viewport = options.keepPreview ? el.viewerPanel.getBoundingClientRect() : null;
+	const previewIDs = viewport ? [...state.visiblePages].filter((index) => {
+		const bounds = pageShell(index)?.getBoundingClientRect();
+		return bounds && bounds.bottom > viewport.top && bounds.top < viewport.bottom;
+	}).map((index) => state.doc.pages[index].id) : [];
+	const thumbnailPreviews = options.preserveThumbnails ? new Map([...state.pageCache.values()]
+		.filter((page) => page.id !== state.doc.pages[state.pageIndex].id).map((page) => [page.id, page])) : null;
 	if (!state.ready || state.wasmExited) {
 		await ensureWASM();
 	}
@@ -3958,6 +3965,12 @@ async function openDocument(options = {}) {
 		if (options.keepPreview) {
 			resetPageLoading();
 			state.pageCache.clear();
+			if (thumbnailPreviews) {
+				for (const page of doc.pages) {
+					const preview = thumbnailPreviews.get(page.id);
+					if (preview) state.pageCache.set(page.index, { ...preview, previewOnly: true });
+				}
+			}
 			const indices = new Set([pageIndex, ...doc.pages.filter((page) => previewIDs.includes(page.id)).map((page) => page.index)]);
 			for (const index of indices) {
 				await loadPageData(index, { openSeq, priority: 0, refresh: true });
@@ -3977,7 +3990,7 @@ async function openDocument(options = {}) {
 		renderPageFlow();
 		if (options.keepPreview) {
 			for (const [index, page] of state.pageCache) {
-				mountPageSVG(index, page, openSeq);
+				if (!page.previewOnly) mountPageSVG(index, page, openSeq);
 			}
 			releasePageResources();
 		}
@@ -4347,7 +4360,7 @@ async function exportFile(whole, indices = null, value = el.exportFormat.value,
 		return;
 	}
 	const saving = value === "ofd";
-	if (saving && !state.editorInfo && !encryption) {
+	if (saving && !state.editorInfo && !state.ofdBytes && !encryption) {
 		return;
 	}
 	if (!saving && state.doc.encryption?.encrypted && !window.confirm("此格式将输出明文，是否继续？")) return;
@@ -4388,12 +4401,21 @@ async function exportFile(whole, indices = null, value = el.exportFormat.value,
 			delete encryption.recipientFiles;
 			if (openSeq !== state.openSeq) return;
 		}
-		const result = encryption ? await callWASM("ofdgoSaveEncrypted", indices, encryption, file) : saving ? await callWASM("ofdgoSaveDocument", indices, file) : whole
+		const readingSave = saving && !state.editorInfo && !encryption && indices === null;
+		const result = readingSave
+			? { label: "OFD", size: state.ofdBytes.byteLength, mime, blob: state.ofdBytes }
+			: encryption ? await callWASM("ofdgoSaveEncrypted", indices, encryption, file) : saving ? await callWASM("ofdgoSaveDocument", indices, file) : whole
 			? await callWASM("ofdgoExportDocument", format.value, dpi, indices, state.renderBackend, file)
 			: await callWASM("ofdgoExportPage", pageIndex, format.value, dpi, state.renderBackend, file);
 		if (openSeq !== state.openSeq) {
 			return;
 		}
+		if (readingSave && file) {
+			const writer = await file.createWritable();
+			await writer.write(result.blob);
+			await writer.close();
+			delete result.blob;
+		}
 		if (result.blob) {
 			downloadBytes(result.blob, result.mime, fileName);
 		}
@@ -4655,7 +4677,8 @@ async function renderFlowPage(index, options = {}) {
 		return null;
 	}
 	try {
-		const page = await loadPageData(index, { openSeq, priority: options.priority ?? 2 });
+		const page = await loadPageData(index, { openSeq, priority: options.priority ?? 2,
+			refresh: state.editing && state.pageCache.get(index)?.previewOnly });
 		if (openSeq !== state.openSeq) {
 			return null;
 		}
@@ -7147,7 +7170,8 @@ function updateEditorTools() {
 	el.editorTools.hidden = !state.editing;
 	const pagesDisabled = !state.editing || !state.ready || state.exporting;
 	el.insertTextButton.disabled = el.insertImageButton.disabled = pagesDisabled || !pageCan("insert");
-	el.saveButton.disabled = el.addPageButton.disabled = pagesDisabled;
+	el.saveButton.disabled = !state.doc || !state.ready || state.exporting || (!state.editorInfo && !state.ofdBytes);
+	el.addPageButton.disabled = pagesDisabled;
 	const selectedPages = state.editing ? selectedPageIndexes() : [state.pageIndex];
 	const selectionDisabled = pagesDisabled || !selectedPages.length;
 	el.batchPagesButton.disabled = selectionDisabled;

go.mod

@@ -9,7 +9,7 @@ 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 v0.0.0-20260924110344-e481bdea25e9
+	github.com/xiaoqidun/pdfgo v0.0.0-20260924121050-2d9bc5cc700d
 	golang.org/x/crypto v0.57.0
 	golang.org/x/image v0.46.0
 	golang.org/x/text v0.42.0

go.sum

@@ -60,8 +60,8 @@ 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 v0.0.0-20260924110344-e481bdea25e9 h1:MjDKg9lMG/5AmEr+SV7C2y4dzfhpfXDSYScfu2mZixQ=
-github.com/xiaoqidun/pdfgo v0.0.0-20260924110344-e481bdea25e9/go.mod h1:/D0XHgfZ7xNhix95swpNaThpuqoJjVR5wIadogtR5pI=
+github.com/xiaoqidun/pdfgo v0.0.0-20260924121050-2d9bc5cc700d h1:ko1gZlKK5MvOjjTxr1tYyysVlWVIDvgVi+bogBi6pUw=
+github.com/xiaoqidun/pdfgo v0.0.0-20260924121050-2d9bc5cc700d/go.mod h1:/D0XHgfZ7xNhix95swpNaThpuqoJjVR5wIadogtR5pI=
 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_pdf.go

@@ -113,13 +113,12 @@ func ImportPDF(ctx context.Context, source io.ReaderAt, size int64, options PDFI
 		if err := importer.flushPath(); err != nil {
 			return fmt.Errorf("import PDF page %d: %w", index+1, err)
 		}
-		if err := importer.links(page); err != nil {
+		if err := importer.annotations(ctx, page); err != nil {
 			return fmt.Errorf("import PDF page %d: %w", index+1, err)
 		}
-		if _, err := editor.CopyObjects(importer.page, importer.objects, 0, 0); err != nil {
+		if err := importer.commitObjects(); err != nil {
 			return fmt.Errorf("import PDF page %d: %w", index+1, err)
 		}
-		importer.objects = nil
 		importer.report.Pages++
 		if options.Progress != nil {
 			return options.Progress(index + 1)
@@ -135,6 +134,19 @@ func ImportPDF(ctx context.Context, source io.ReaderAt, size int64, options PDFI
 	return editor, importer.report, nil
 }
 
+// commitObjects 将当前页面待转换对象写入编辑文档
+// 返回: error 对象写入错误
+func (p *pdfImporter) commitObjects() error {
+	if len(p.objects) == 0 {
+		return nil
+	}
+	if _, err := p.editor.CopyObjects(p.page, p.objects, 0, 0); err != nil {
+		return err
+	}
+	p.objects = nil
+	return nil
+}
+
 // ConvertPDF 将PDF转换并写入OFD，转换阶段失败时不写入目标
 // 入参: ctx 取消上下文, source PDF数据, size 字节数, output OFD输出, options 转换选项
 // 返回: PDFImportReport 转换统计, error 错误信息
@@ -265,6 +277,9 @@ func (p *pdfImporter) clips(paths []pdfgo.Path, origin Box) *Clips {
 // 入参: mark PDF路径绘制信息
 // 返回: error 错误信息
 func (p *pdfImporter) path(mark pdfgo.PathMark) error {
+	if mark.Style.BlendMode == "Multiply" {
+		return &pdfgo.UnsupportedError{Feature: "multiply path"}
+	}
 	if !mark.Stroke || mark.Fill || mark.Style.Stroke.Alpha != 1 {
 		if err := p.flushPath(); err != nil {
 			return err

ofdgo_pdf_annot.go

@@ -0,0 +1,172 @@
+// 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"
+	"image/color"
+	"image/png"
+	"math"
+
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// signatureWidget 转换可见签名外观，不将PDF签名误写成OFD签名
+// 入参: ctx 取消上下文, page PDF页面, annotation 签名控件
+// 返回: error 外观或转换错误
+func (p *pdfImporter) signatureWidget(ctx context.Context, page *pdfgo.Page, annotation pdfgo.Annotation) error {
+	if annotation.Dictionary["FT"] != pdfgo.Name("Sig") || annotation.Dictionary["V"] == nil {
+		return &pdfgo.UnsupportedError{Feature: "non-signature widget"}
+	}
+	flags := int64(0)
+	if value := annotation.Dictionary["F"]; value != nil {
+		resolved, err := p.reader.Resolve(value)
+		if err != nil {
+			return err
+		}
+		number, ok := resolved.(pdfgo.Integer)
+		if !ok {
+			return fmt.Errorf("invalid PDF annotation flags")
+		}
+		flags = int64(number)
+	}
+	const invisibleFlags = 1 | 2 | 32
+	if flags&invisibleFlags != 0 {
+		p.report.Warnings = append(p.report.Warnings, pdfgo.Diagnostic{Page: p.page + 1, Message: "hidden PDF signature not transferred"})
+		return nil
+	}
+	var images []pdfgo.ImageMark
+	visitor := pdfgo.Visitor{
+		Path: func(pdfgo.PathMark) error { return &pdfgo.UnsupportedError{Feature: "signature appearance path"} },
+		Text: func(pdfgo.TextMark) error { return &pdfgo.UnsupportedError{Feature: "signature appearance text"} },
+		Image: func(mark pdfgo.ImageMark) error {
+			images = append(images, mark)
+			return nil
+		},
+	}
+	if err := p.reader.WalkAnnotationAppearance(ctx, page, annotation, visitor); err != nil {
+		return err
+	}
+	if len(images) != 1 {
+		return &pdfgo.UnsupportedError{Feature: "signature appearance composition"}
+	}
+	mark := images[0]
+	message := "PDF signature appearance imported; digital signature not transferred"
+	if mark.Style.BlendMode == "Multiply" {
+		if err := p.multiplySignatureAppearance(page, annotation, mark); err != nil {
+			return err
+		}
+		message = "PDF signature appearance flattened over page content; digital signature not transferred"
+	} else if mark.Style.BlendMode == "" || mark.Style.BlendMode == "Normal" || mark.Style.BlendMode == "Compatible" {
+		if err := p.image(mark); err != nil {
+			return err
+		}
+	} else {
+		return &pdfgo.UnsupportedError{Feature: "signature appearance blend mode"}
+	}
+	p.report.Warnings = append(p.report.Warnings, pdfgo.Diagnostic{Page: p.page + 1, Message: message})
+	return nil
+}
+
+// multiplySignatureAppearance 合成签名覆盖区域，正文及其他页面对象保持独立
+// 入参: page PDF页面, annotation 签名控件, mark 印章图像
+// 返回: error 图像或渲染错误
+func (p *pdfImporter) multiplySignatureAppearance(page *pdfgo.Page, annotation pdfgo.Annotation, mark pdfgo.ImageMark) error {
+	if err := p.commitObjects(); err != nil {
+		return err
+	}
+	base, err := renderImportedPage(p.editor, p.page)
+	if err != nil {
+		return err
+	}
+	_, width, height := pdfPageMatrix(page)
+	appearance := NewEditor()
+	appearance.SetRenderBackends(p.editor.backends)
+	if _, err := appearance.AddPage(width, height); err != nil {
+		return err
+	}
+	stamp := pdfImporter{reader: p.reader, editor: appearance, matrix: p.matrix, pageBox: page.CropBox}
+	mark.Style.BlendMode = "Normal"
+	if err := stamp.image(mark); err != nil {
+		return err
+	}
+	if _, err := appearance.CopyObjects(0, stamp.objects, 0, 0); err != nil {
+		return err
+	}
+	overlay, err := renderImportedPage(appearance, 0)
+	if err != nil {
+		return err
+	}
+	if base.Bounds() != overlay.Bounds() {
+		return fmt.Errorf("signature appearance page size mismatch")
+	}
+	annotationBox := annotation.Rect
+	box := pdfBounds([]pdfgo.Point{
+		p.matrix.Apply(pdfgo.Point{X: annotationBox.XMin, Y: annotationBox.YMin}),
+		p.matrix.Apply(pdfgo.Point{X: annotationBox.XMax, Y: annotationBox.YMin}),
+		p.matrix.Apply(pdfgo.Point{X: annotationBox.XMax, Y: annotationBox.YMax}),
+		p.matrix.Apply(pdfgo.Point{X: annotationBox.XMin, Y: annotationBox.YMax}),
+	})
+	const dpi = 300.0
+	pixelsPerMM := dpi / 25.4
+	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())
+	if region.Empty() {
+		return fmt.Errorf("signature appearance outside page")
+	}
+	composite := image.NewRGBA(image.Rect(0, 0, region.Dx(), region.Dy()))
+	for y := region.Min.Y; y < region.Max.Y; y++ {
+		for x := region.Min.X; x < region.Max.X; x++ {
+			background := color.RGBAModel.Convert(base.At(x, y)).(color.RGBA)
+			foreground := color.RGBAModel.Convert(overlay.At(x, y)).(color.RGBA)
+			composite.SetRGBA(x-region.Min.X, y-region.Min.Y, color.RGBA{
+				R: uint8((int(background.R)*int(foreground.R) + 127) / 255),
+				G: uint8((int(background.G)*int(foreground.G) + 127) / 255),
+				B: uint8((int(background.B)*int(foreground.B) + 127) / 255),
+				A: 255,
+			})
+		}
+	}
+	var encoded bytes.Buffer
+	if err := png.Encode(&encoded, composite); err != nil {
+		return err
+	}
+	id, err := p.editor.AddImage(encoded.Bytes())
+	if err != nil {
+		return err
+	}
+	regionBox := Box{X: float64(region.Min.X) / pixelsPerMM, Y: float64(region.Min.Y) / pixelsPerMM, W: float64(region.Dx()) / pixelsPerMM, H: float64(region.Dy()) / pixelsPerMM}
+	p.objects = append(p.objects, GraphicObject{Type: "ImageObject", ImageObject: ImageObject{Boundary: pdfBoundary(regionBox), ResourceID: id}})
+	p.report.ImageObjects++
+	return nil
+}
+
+// renderImportedPage 在固定印刷分辨率绘制待合成页面
+// 入参: editor 编辑文档, page 页序号
+// 返回: image.Image 页面像素, error 渲染错误
+func renderImportedPage(editor *Editor, page int) (image.Image, error) {
+	reader, err := editor.Reader()
+	if err != nil {
+		return nil, err
+	}
+	defer reader.Close()
+	content, err := reader.PageContentByIndex(page)
+	if err != nil {
+		return nil, err
+	}
+	return NewRenderer(reader, WithDPI(300), WithRenderBackends(editor.backends)).RenderToImage(content)
+}

ofdgo_pdf_link.go

@@ -15,21 +15,28 @@
 package ofdgo
 
 import (
+	"context"
 	"fmt"
 
 	"github.com/xiaoqidun/pdfgo"
 )
 
-// links 将无外观链接转换为OFD点击区域，其他注解或外观返回不支持错误
-// 入参: page PDF页面
+// annotations 将链接和签名外观按页面顺序转换为OFD对象
+// 入参: ctx 取消上下文, page PDF页面
 // 返回: error 错误信息
-func (p *pdfImporter) links(page *pdfgo.Page) error {
+func (p *pdfImporter) annotations(ctx context.Context, page *pdfgo.Page) error {
 	annotations, err := page.Annotations()
 	if err != nil {
 		return err
 	}
 	for _, annotation := range annotations {
 		dict := annotation.Dictionary
+		if annotation.Subtype == "Widget" {
+			if err := p.signatureWidget(ctx, page, annotation); err != nil {
+				return err
+			}
+			continue
+		}
 		if annotation.Subtype != "Link" {
 			return &pdfgo.UnsupportedError{Feature: "annotation " + string(annotation.Subtype)}
 		}

ofdgo_pdf_object.go

@@ -33,6 +33,9 @@ import (
 // 入参: mark PDF图像绘制信息
 // 返回: error 错误信息
 func (p *pdfImporter) image(mark pdfgo.ImageMark) error {
+	if mark.Style.BlendMode == "Multiply" {
+		return &pdfgo.UnsupportedError{Feature: "multiply image outside annotation appearance"}
+	}
 	if err := p.flushPath(); err != nil {
 		return err
 	}
@@ -113,6 +116,9 @@ func (p *pdfImporter) image(mark pdfgo.ImageMark) error {
 // 入参: mark PDF文字绘制信息
 // 返回: error 错误信息
 func (p *pdfImporter) text(mark pdfgo.TextMark) error {
+	if mark.Style.BlendMode == "Multiply" {
+		return &pdfgo.UnsupportedError{Feature: "multiply text"}
+	}
 	if err := p.flushPath(); err != nil {
 		return err
 	}
@@ -209,11 +215,15 @@ func (p *pdfImporter) text(mark pdfgo.TextMark) error {
 	box := pdfBounds(points)
 	fill, stroke, visible := mark.Mode == 0 || mark.Mode == 2, mark.Mode == 1 || mark.Mode == 2, mark.Mode != 3
 	if stroke {
-		margin := mark.Style.LineWidth * unit * math.Hypot(m[0], m[1]) / 2 * math.Max(1, mark.Style.MiterLimit)
+		scale := math.Sqrt(math.Abs(m[0]*m[3] - m[1]*m[2]))
+		if scale == 0 || math.IsNaN(scale) || math.IsInf(scale, 0) {
+			return &pdfgo.UnsupportedError{Feature: "degenerate text stroke matrix"}
+		}
+		margin := mark.Style.LineWidth * unit / 2 * math.Max(1, mark.Style.MiterLimit)
 		box = Box{box.X - margin, box.Y - margin, box.W + 2*margin, box.H + 2*margin}
 		color := StrokeColor(*p.color(mark.Style.Stroke))
 		object.StrokeColor = &color
-		object.LineWidth = mark.Style.LineWidth * unit
+		object.LineWidth = mark.Style.LineWidth * unit / scale
 		object.LineWidthSet = object.LineWidth == 0
 		object.Join = []string{"Miter", "Round", "Bevel"}[mark.Style.Join]
 		object.MiterLimit = mark.Style.MiterLimit