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fix: keep oversized inline image on one page in DOCX rendering #134

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Merged
shps951023 merged 3 commits into from
Sep 5, 2026
Merged

fix: keep oversized inline image on one page in DOCX rendering #134

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a647db4
fix: move oversized inline image to next page in DOCX rendering
dks50217 Sep 5, 2026
2453813
test: cover inline image page-break in DOCX rendering
dks50217 Sep 5, 2026
3da0da2
fix: flow inline image to next column before forcing a page break
dks50217 Sep 5, 2026
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17 changes: 14 additions & 3 deletions src/MiniPdf/DocxToPdfConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -173,7 +173,7 @@
// Calibri widths can under-wrap and reduce page count.
if (!string.IsNullOrWhiteSpace(docxDoc.DefaultFontName))
{
options.UseCalibriWidths = docxDoc.DefaultFontName.Contains("Calibri", StringComparison.OrdinalIgnoreCase);

Check warning on line 176 in src/MiniPdf/DocxToPdfConverter.cs

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Possible null reference argument for parameter 's' in 'bool NetFxPolyfills.Contains(string s, string value, StringComparison comparison)'.
s_serifFont = IsSerifFont(docxDoc.DefaultFontName);
s_defaultFontName = docxDoc.DefaultFontName;
}
Expand Down Expand Up @@ -3362,9 +3362,20 @@
height *= scale;
}

// Check if image fits on current page
if (state.CurrentY - height < state.Options.MarginBottom)
state.EnsurePage();
// Move the whole image to the next column/page when it does not fit in
// the remaining space. Word keeps an inline image intact rather than
// clipping it at the bottom. EnsurePage only adds a page once the cursor
// is already past the bottom margin, which leaves a partial image
// clipped, so handle the break here. In a multi-column section flow to
// the next column first (as EnsurePage does); only force a new page when
// no column remains. Skip entirely when already at the top of a fresh
// column/page, otherwise an image taller than the usable area would push
// out a blank column/page ahead of it (Word overflows there).
if (state.CurrentY - height < state.Options.MarginBottom && !state.IsTopOfPage)
{
if (!(state.ColumnCount > 1 && state.AdvanceToNextColumn()))
state.ForceNewPage();
}

var x = state.Options.MarginLeft;
if (image.IsWrapTopBottom)
Expand Down
135 changes: 135 additions & 0 deletions tests/MiniPdf.Tests/DocxToPdfConverterTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -274,6 +274,44 @@ public void Convert_DocxWithRootRelativeImageRelationship_RendersImage()
Assert.Contains(doc.Pages, page => page.ImageBlocks.Count > 0);
}

[Fact]
public void Convert_InlineImageThatDoesNotFit_MovesToNextPageWithoutClipping()
{
// Small page so a few filler lines plus a moderate image cannot share one page.
var options = new DocxToPdfConverter.ConversionOptions
{
PageWidth = 400,
PageHeight = 400,
MarginTop = 40,
MarginBottom = 40,
MarginLeft = 40,
MarginRight = 40,
};
// ~260pt image: fits on a fresh page (usable height 320) but not once the
// filler lines have consumed most of page 1.
const long imageEmu = 260L * 12700L;
using var docxStream = CreateDocxWithFillerThenTallImage(
fillerParagraphs: 10, imageCxEmu: imageEmu, imageCyEmu: imageEmu);

var doc = DocxToPdfConverter.Convert(docxStream, options);

var placed = doc.Pages
.Select((page, index) => (page, index))
.SelectMany(entry => entry.page.ImageBlocks.Select(block => (entry.index, block)))
.ToList();
Assert.Single(placed);
var (pageIndex, image) = placed[0];

// The whole image must move to a later page rather than being clipped at the
// bottom of page 1 (the behavior this fix restores).
Assert.True(pageIndex >= 1, $"Expected the image on a page after the first; got page {pageIndex + 1}.");
// And it must sit fully inside the printable area, not off the bottom edge.
Assert.True(image.Y >= options.MarginBottom,
$"Image bottom {image.Y} is below the bottom margin {options.MarginBottom} (clipped).");
Assert.True(image.Y + image.RenderHeight <= options.PageHeight - options.MarginTop + 0.5f,
$"Image top {image.Y + image.RenderHeight} exceeds the printable area.");
}

private static void AssertXrefOffsetsAreCorrect(byte[] pdfBytes)
{
var text = Encoding.GetEncoding("iso-8859-1").GetString(pdfBytes);
Expand Down Expand Up @@ -408,6 +446,103 @@ private static MemoryStream CreateDocxWithPngImage(
return ms;
}

/// <summary>
/// Builds a DOCX with a run of filler paragraphs followed by a single inline
/// image of the given EMU size, used to exercise page-break handling when the
/// image cannot fit in the remaining space on the current page.
/// </summary>
private static MemoryStream CreateDocxWithFillerThenTallImage(
int fillerParagraphs, long imageCxEmu, long imageCyEmu)
{
var ms = new MemoryStream();
var pngBytes = CreateMinimalRgbaPng(4, 4);

var filler = string.Concat(Enumerable.Range(0, fillerParagraphs)
.Select(i => $"<w:p><w:r><w:t>Filler line {i}</w:t></w:r></w:p>"));

using (var archive = new ZipArchive(ms, ZipArchiveMode.Create, leaveOpen: true))
{
AddEntry(archive, "[Content_Types].xml",
"""
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
<Default Extension="xml" ContentType="application/xml"/>
<Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
<Default Extension="png" ContentType="image/png"/>
<Override PartName="/word/document.xml" ContentType="application/vnd.openxmlformats-officedocument.wordprocessingml.document.main+xml"/>
</Types>
""");

AddEntry(archive, "_rels/.rels",
"""
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="word/document.xml"/>
</Relationships>
""");

AddEntry(archive, "word/_rels/document.xml.rels",
"""
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
<Relationship Id="rId10" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image" Target="media/image1.png"/>
</Relationships>
""");

AddEntry(archive, "word/document.xml",
$$"""
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<w:document xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main"
xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships"
xmlns:wp="http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing"
xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main"
xmlns:pic="http://schemas.openxmlformats.org/drawingml/2006/picture">
<w:body>
{{filler}}
<w:p>
<w:r>
<w:drawing>
<wp:inline distT="0" distB="0" distL="0" distR="0">
<wp:extent cx="{{imageCxEmu}}" cy="{{imageCyEmu}}"/>
<wp:docPr id="1" name="Picture 1"/>
<a:graphic>
<a:graphicData uri="http://schemas.openxmlformats.org/drawingml/2006/picture">
<pic:pic>
<pic:nvPicPr>
<pic:cNvPr id="1" name="image1.png"/>
<pic:cNvPicPr/>
</pic:nvPicPr>
<pic:blipFill>
<a:blip r:embed="rId10"/>
<a:stretch><a:fillRect/></a:stretch>
</pic:blipFill>
<pic:spPr>
<a:xfrm>
<a:off x="0" y="0"/>
<a:ext cx="{{imageCxEmu}}" cy="{{imageCyEmu}}"/>
</a:xfrm>
<a:prstGeom prst="rect"><a:avLst/></a:prstGeom>
</pic:spPr>
</pic:pic>
</a:graphicData>
</a:graphic>
</wp:inline>
</w:drawing>
</w:r>
</w:p>
</w:body>
</w:document>
""");

var imgEntry = archive.CreateEntry("word/media/image1.png");
using (var imgStream = imgEntry.Open())
imgStream.Write(pngBytes, 0, pngBytes.Length);
}

ms.Position = 0;
return ms;
}

/// <summary>Creates a minimal valid RGBA PNG file (with alpha channel).</summary>
private static byte[] CreateMinimalRgbaPng(int width, int height)
{
Expand Down
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