Analyzing PDF Font Properties with PDFium VCL in Delphi

Understanding the fonts used in a PDF document is essential for quality control, accessibility compliance, and document forensics. The Font Properties demo shows how to access detailed font information for characters in a PDF using PDFium VCL.

Overview

This demo allows you to click on any character in a PDF and view its font properties including family name, weight, style, size, and whether the font is embedded. It’s invaluable for PDF analysis and troubleshooting.

Key Features

Interactive Selection – Click on any character to analyze it
Font Family Name – The font family (e.g., “Arial”, “Times New Roman”)
Font Base Name – The internal PDF font name
Font Weight – Numeric weight (400 = normal, 700 = bold)
Font Size – Size in points
Italic Angle – Slant angle for italic fonts
Ascent/Descent – Vertical metrics
Embedded Status – Whether the font is embedded in the PDF
Font Data – Access raw font data if embedded

PDFium DLL Requirements

Before running any PDFium VCL application, ensure the PDFium DLL files are installed:

pdfium32.dll / pdfium64.dll – Standard versions (~5-6 MB)
pdfium32v8.dll / pdfium64v8.dll – With V8 JavaScript engine (~23-27 MB)

Installation: Run PDFiumVCL\DLLs\CopyDlls.bat as Administrator to automatically copy the DLLs to Windows system directories.

Accessing Font Properties

procedure TfrmMain.UpdateFontInfo;
var
  FontInfo: TStringList;
begin
  FontInfo := TStringList.Create;
  try
    FontInfo.Add('=== Font Properties for Character Index: ' + 
      IntToStr(PdfView.CurrentCharIndex) + ' ===');
    FontInfo.Add('');
    
    // Font family name
    try
      FontInfo.Add('Font Family Name: ' + PdfView.FontFamilyName);
    except
      FontInfo.Add('Font Family Name: \u003cError retrieving\u003e');
    end;
    
    // Font base name (internal PDF name)
    try
      FontInfo.Add('Font Base Name: ' + PdfView.FontBaseName);
    except
      FontInfo.Add('Font Base Name: \u003cError retrieving\u003e');
    end;
    
    // Font size for this character
    try
      FontInfo.Add('Font Size: ' + 
        FloatToStr(PdfView.FontSize[PdfView.CurrentCharIndex]));
    except
      FontInfo.Add('Font Size: \u003cError retrieving\u003e');
    end;
    
    // Font weight (400=normal, 700=bold)
    try
      FontInfo.Add('Font Weight: ' + IntToStr(PdfView.FontWeight));
    except
      FontInfo.Add('Font Weight: \u003cError retrieving\u003e');
    end;
    
    // Italic angle (0 for upright, negative for italic)
    try
      FontInfo.Add('Font Italic Angle: ' + IntToStr(PdfView.FontItalicAngle));
    except
      FontInfo.Add('Font Italic Angle: \u003cError retrieving\u003e');
    end;
    
    // Vertical metrics
    try
      FontInfo.Add('Font Ascent: ' + FloatToStr(PdfView.FontAscent));
    except
      FontInfo.Add('Font Ascent: \u003cError retrieving\u003e');
    end;
    
    try
      FontInfo.Add('Font Descent: ' + FloatToStr(PdfView.FontDescent));
    except
      FontInfo.Add('Font Descent: \u003cError retrieving\u003e');
    end;
    
    // Embedded status
    try
      FontInfo.Add('Font Is Embedded: ' + 
        BoolToStr(PdfView.FontIsEmbedded, True));
    except
      FontInfo.Add('Font Is Embedded: \u003cError retrieving\u003e');
    end;
    
    // Font data size (if embedded)
    try
      FontInfo.Add('Font Data Size: ' + 
        IntToStr(Length(PdfView.FontData)) + ' bytes');
    except
      FontInfo.Add('Font Data Size: \u003cError retrieving\u003e');
    end;
    
    FontInfo.Add('');
    FontInfo.Add('Character: ' + 
      PdfView.Character[PdfView.CurrentCharIndex]);
    
    memoFontInfo.Lines.Assign(FontInfo);
    
  finally
    FontInfo.Free;
  end;
end;

procedure TfrmMain.UpdateFontInfo;

var

FontInfo: TStringList;

begin

FontInfo := TStringList.Create;

try

FontInfo.Add('=== Font Properties for Character Index: ' +

IntToStr(PdfView.CurrentCharIndex) + ' ===');

FontInfo.Add('');

// Font family name

try

FontInfo.Add('Font Family Name: ' + PdfView.FontFamilyName);

except

FontInfo.Add('Font Family Name: \u003cError retrieving\u003e');

end;

// Font base name (internal PDF name)

try

FontInfo.Add('Font Base Name: ' + PdfView.FontBaseName);

except

FontInfo.Add('Font Base Name: \u003cError retrieving\u003e');

end;

// Font size for this character

try

FontInfo.Add('Font Size: ' +

FloatToStr(PdfView.FontSize[PdfView.CurrentCharIndex]));

except

FontInfo.Add('Font Size: \u003cError retrieving\u003e');

end;

// Font weight (400=normal, 700=bold)

try

FontInfo.Add('Font Weight: ' + IntToStr(PdfView.FontWeight));

except

FontInfo.Add('Font Weight: \u003cError retrieving\u003e');

end;

// Italic angle (0 for upright, negative for italic)

try

FontInfo.Add('Font Italic Angle: ' + IntToStr(PdfView.FontItalicAngle));

except

FontInfo.Add('Font Italic Angle: \u003cError retrieving\u003e');

end;

// Vertical metrics

try

FontInfo.Add('Font Ascent: ' + FloatToStr(PdfView.FontAscent));

except

FontInfo.Add('Font Ascent: \u003cError retrieving\u003e');

end;

try

FontInfo.Add('Font Descent: ' + FloatToStr(PdfView.FontDescent));

except

FontInfo.Add('Font Descent: \u003cError retrieving\u003e');

end;

// Embedded status

try

FontInfo.Add('Font Is Embedded: ' +

BoolToStr(PdfView.FontIsEmbedded, True));

except

FontInfo.Add('Font Is Embedded: \u003cError retrieving\u003e');

end;

// Font data size (if embedded)

try

FontInfo.Add('Font Data Size: ' +

IntToStr(Length(PdfView.FontData)) + ' bytes');

except

FontInfo.Add('Font Data Size: \u003cError retrieving\u003e');

end;

FontInfo.Add('');

FontInfo.Add('Character: ' +

PdfView.Character[PdfView.CurrentCharIndex]);

memoFontInfo.Lines.Assign(FontInfo);

finally

FontInfo.Free;

end;

Click to Analyze Character

procedure TfrmMain.PdfViewMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  CharIndex: Integer;
begin
  if not PdfView.Active then
    Exit;
    
  try
    // Get character at click position
    CharIndex := PdfView.CharacterIndexAtPos(X, Y, 10.0, 10.0);
    
    if CharIndex &gt;= 0 then
    begin
      edtCharIndex.Text := IntToStr(CharIndex);
      PdfView.CurrentCharIndex := CharIndex;
      UpdateFontInfo;
    end;
    
  except
    on E: Exception do
    begin
      memoFontInfo.Lines.Clear;
      memoFontInfo.Lines.Add('Error getting character: ' + E.Message);
    end;
  end;
end;

procedure TfrmMain.PdfViewMouseDown(Sender: TObject; Button: TMouseButton;

Shift: TShiftState; X, Y: Integer);

var

CharIndex: Integer;

begin

if not PdfView.Active then

Exit;

try

// Get character at click position

CharIndex := PdfView.CharacterIndexAtPos(X, Y, 10.0, 10.0);

if CharIndex >= 0 then

begin

edtCharIndex.Text := IntToStr(CharIndex);

PdfView.CurrentCharIndex := CharIndex;

UpdateFontInfo;

end;

except

on E: Exception do

begin

memoFontInfo.Lines.Clear;

memoFontInfo.Lines.Add('Error getting character: ' + E.Message);

end;

Manual Character Index Input

procedure TfrmMain.btnGetFontInfoClick(Sender: TObject);
var
  CharIndex: Integer;
begin
  if not PdfView.Active then
  begin
    ShowMessage('Please open a PDF file first.');
    Exit;
  end;
  
  try
    CharIndex := StrToInt(edtCharIndex.Text);
    PdfView.CurrentCharIndex := CharIndex;
    UpdateFontInfo;
  except
    on E: Exception do
      ShowMessage('Invalid character index: ' + E.Message);
  end;
end;

procedure TfrmMain.btnGetFontInfoClick(Sender: TObject);

var

CharIndex: Integer;

begin

if not PdfView.Active then

begin

ShowMessage('Please open a PDF file first.');

Exit;

end;

try

CharIndex := StrToInt(edtCharIndex.Text);

PdfView.CurrentCharIndex := CharIndex;

UpdateFontInfo;

except

on E: Exception do

ShowMessage('Invalid character index: ' + E.Message);

end;

Font Properties Available

PDFium VCL exposes these font-related properties:

// Font properties accessible via TPdf and TPdfView
property FontFamilyName: WString;  // e.g., "Arial", "Times New Roman"
property FontBaseName: WString;    // Internal PDF font name
property FontWeight: Integer;      // 100-900, 400=normal, 700=bold
property FontItalicAngle: Integer; // Degrees, 0=upright, negative=italic
property FontAscent: Single;       // Height above baseline
property FontDescent: Single;      // Depth below baseline (negative)
property FontIsEmbedded: Boolean;  // True if font is embedded
property FontData: TBytes;         // Raw font data if embedded
property FontHandle: FPDF_FONT;    // PDFium font handle

// Per-character property
property FontSize[Index: Integer]: Double;  // Font size for character

// Font properties accessible via TPdf and TPdfView

property FontFamilyName: WString; // e.g., "Arial", "Times New Roman"

property FontBaseName: WString; // Internal PDF font name

property FontWeight: Integer; // 100-900, 400=normal, 700=bold

property FontItalicAngle: Integer; // Degrees, 0=upright, negative=italic

property FontAscent: Single; // Height above baseline

property FontDescent: Single; // Depth below baseline (negative)

property FontIsEmbedded: Boolean; // True if font is embedded

property FontData: TBytes; // Raw font data if embedded

property FontHandle: FPDF_FONT; // PDFium font handle

// Per-character property

property FontSize[Index: Integer]: Double; // Font size for character

Using Font Properties for Analysis

procedure AnalyzeDocumentFonts(Pdf: TPdf);
var
  FontList: TStringList;
  I: Integer;
  FontName: string;
  LastFontName: string;
begin
  FontList := TStringList.Create;
  FontList.Sorted := True;
  FontList.Duplicates := dupIgnore;
  
  try
    Pdf.PageNumber := 1;
    LastFontName := '';
    
    for I := 0 to Pdf.CharacterCount - 1 do
    begin
      // Access font for each character
      // (In practice, use CurrentCharIndex pattern)
      
      // Check FontFamilyName changes
      // Add unique fonts to list
    end;
    
    ShowMessage('Document uses ' + IntToStr(FontList.Count) + ' fonts');
    
  finally
    FontList.Free;
  end;
end;

procedure AnalyzeDocumentFonts(Pdf: TPdf);

var

FontList: TStringList;

I: Integer;

FontName: string;

LastFontName: string;

begin

FontList := TStringList.Create;

FontList.Sorted := True;

FontList.Duplicates := dupIgnore;

try

Pdf.PageNumber := 1;

LastFontName := '';

for I := 0 to Pdf.CharacterCount - 1 do

begin

// Access font for each character

// (In practice, use CurrentCharIndex pattern)

// Check FontFamilyName changes

// Add unique fonts to list

end;

ShowMessage('Document uses ' + IntToStr(FontList.Count) + ' fonts');

finally

FontList.Free;

end;

Checking Font Embedding

procedure CheckFontEmbedding(Pdf: TPdf);
var
  EmbeddedFonts, NonEmbeddedFonts: TStringList;
begin
  EmbeddedFonts := TStringList.Create;
  NonEmbeddedFonts := TStringList.Create;
  
  try
    EmbeddedFonts.Sorted := True;
    EmbeddedFonts.Duplicates := dupIgnore;
    NonEmbeddedFonts.Sorted := True;
    NonEmbeddedFonts.Duplicates := dupIgnore;
    
    // Analyze fonts...
    
    if NonEmbeddedFonts.Count &gt; 0 then
    begin
      ShowMessage('Warning: ' + IntToStr(NonEmbeddedFonts.Count) + 
        ' fonts are not embedded. Document may not display correctly ' +
        'on systems without these fonts installed.');
    end
    else
    begin
      ShowMessage('All fonts are embedded. Document will display ' +
        'consistently on all systems.');
    end;
    
  finally
    EmbeddedFonts.Free;
    NonEmbeddedFonts.Free;
  end;
end;

procedure CheckFontEmbedding(Pdf: TPdf);

var

EmbeddedFonts, NonEmbeddedFonts: TStringList;

begin

EmbeddedFonts := TStringList.Create;

NonEmbeddedFonts := TStringList.Create;

try

EmbeddedFonts.Sorted := True;

EmbeddedFonts.Duplicates := dupIgnore;

NonEmbeddedFonts.Sorted := True;

NonEmbeddedFonts.Duplicates := dupIgnore;

// Analyze fonts...

if NonEmbeddedFonts.Count > 0 then

begin

ShowMessage('Warning: ' + IntToStr(NonEmbeddedFonts.Count) +

' fonts are not embedded. Document may not display correctly ' +

'on systems without these fonts installed.');

end

else

begin

ShowMessage('All fonts are embedded. Document will display ' +

'consistently on all systems.');

end;

finally

EmbeddedFonts.Free;

NonEmbeddedFonts.Free;

end;

Extracting Embedded Font Data

procedure ExtractEmbeddedFont(Pdf: TPdf; const OutputFile: string);
var
  FontData: TBytes;
  FileStream: TFileStream;
begin
  if Pdf.FontIsEmbedded then
  begin
    FontData := Pdf.FontData;
    
    if Length(FontData) &gt; 0 then
    begin
      FileStream := TFileStream.Create(OutputFile, fmCreate);
      try
        FileStream.WriteBuffer(FontData[0], Length(FontData));
        ShowMessage('Font extracted: ' + IntToStr(Length(FontData)) + ' bytes');
      finally
        FileStream.Free;
      end;
    end;
  end
  else
    ShowMessage('Font is not embedded in the document.');
end;

procedure ExtractEmbeddedFont(Pdf: TPdf; const OutputFile: string);

var

FontData: TBytes;

FileStream: TFileStream;

begin

if Pdf.FontIsEmbedded then

begin

FontData := Pdf.FontData;

if Length(FontData) > 0 then

begin

FileStream := TFileStream.Create(OutputFile, fmCreate);

try

FileStream.WriteBuffer(FontData[0], Length(FontData));

ShowMessage('Font extracted: ' + IntToStr(Length(FontData)) + ' bytes');

finally

FileStream.Free;

end;

end

else

ShowMessage('Font is not embedded in the document.');

end;

Understanding Font Weight Values

Weight Value	Common Name
100	Thin
200	Extra Light
300	Light
400	Normal/Regular
500	Medium
600	Semi Bold
700	Bold
800	Extra Bold
900	Black

Use Cases

Quality Control – Verify correct fonts are used in documents
Accessibility – Check fonts meet accessibility requirements
Forensic Analysis – Analyze document origins and modifications
Print Preflight – Verify font embedding before production
Font Inventory – Catalog fonts used across documents

Conclusion

The Font Properties demo shows how PDFium VCL provides deep access to font information in PDF documents. Whether you’re checking font embedding for print production or analyzing document typography, these APIs give you the tools you need.

The ability to click on any character and instantly see its font properties makes PDF analysis intuitive and efficient.

Explore PDF fonts in depth with PDFium Delphi VCL Component.