Enhanced EMF/WMF Support

Enhanced EMF/WMF Metafile Support

Overview

HotPDF now provides significantly enhanced support for Enhanced Metafile (EMF) and Windows Metafile (WMF) formats The new implementation includes automatic format detection, multiple positioning options, advanced scaling control, and improved rendering quality for vector graphics in PDF documents.

Key Enhancements

Automatic EMF/WMF format detection and appropriate processing
Multiple positioning options (center, top-left, custom coordinates)
Enhanced scaling and aspect ratio control
Per-call rendering options for compression, scaling, reference DC, pen-style handling, hatch-brush preservation, and null object diagnostics
Direct EMF rendering for vector graphics preservation
Bitmap conversion option for compatibility
Improved memory management for large metafiles
Better handling of complex vector graphics and text

Position Control Options

The enhanced metafile support includes flexible positioning options:

mpCenter: Metafile centered on the page (default behavior)
mpLeftTop: Metafile displayed at the top-left corner (X=0, Y=0)
mpCustom: Metafile displayed at specified position (requires X, Y parameters)

Usage Examples

Basic Usage (Default Centered Display)


// Delphi example - Default centered display
procedure ShowMetafileDefault;
var
  PDF: THotPDF;
  MetaFile: TMetafile;
begin
  PDF := THotPDF.Create(nil);
  MetaFile := TMetafile.Create;
  try
    PDF.BeginDoc;
    PDF.AddPage;

    // Load metafile
    MetaFile.LoadFromFile('diagram.emf');

    // Display centered on page (default)
    PDF.CurrentPage.ShowMetafile(MetaFile);

    PDF.EndDoc;
  finally
    MetaFile.Free;
    PDF.Free;
  end;
end;

Position Control Usage


// Delphi example - Advanced positioning
procedure ShowMetafileAdvanced;
var
  PDF: THotPDF;
  MetaFile: TMetafile;
begin
  PDF := THotPDF.Create(nil);
  MetaFile := TMetafile.Create;
  try
    PDF.BeginDoc;
    PDF.AddPage;

    MetaFile.LoadFromFile('chart.wmf');

    // Top-left corner display
    PDF.CurrentPage.ShowMetafile(MetaFile, mpLeftTop);

    // Custom position display
    PDF.CurrentPage.ShowMetafile(MetaFile, mpCustom, 100, 200);

    PDF.EndDoc;
  finally
    MetaFile.Free;
    PDF.Free;
  end;
end;

Per-call Rendering Options


// Delphi example - Per-call options
procedure ShowMetafileWithOptions;
var
  PDF: THotPDF;
  MetaFile: TMetafile;
  Options: THPDFEmfOptions;
begin
  PDF := THotPDF.Create(nil);
  MetaFile := TMetafile.Create;
  Options := THPDFEmfOptions.Create;
  try
    Options.EmfBitmapScale := 1;
    Options.ColorImageCompression := icFlate;
    Options.UseScreenReferenceDC := False;
    Options.CanvasOver := True;
    Options.Redraw := False;
    Options.UseFrame := True;
    Options.ShowNullPen := True;
    Options.ShowNullBrush := True;

    PDF.BeginDoc;
    PDF.AddPage;
    MetaFile.LoadFromFile('diagram.emf');
    PDF.CurrentPage.ShowMetafile(MetaFile, mpCenter, 0, 0, Options);
    PDF.EndDoc;
  finally
    Options.Free;
    MetaFile.Free;
    PDF.Free;
  end;
end;

Enhanced Methods

The enhanced EMF/WMF support introduces several new methods:

THPDFPage.ShowMetafile Overloads

ShowMetafile(MetaFile: TMetafile) - Default centered display
ShowMetafile(MetaFile: TMetafile; Position: THPDFMetafilePosition) - Position control
ShowMetafile(MetaFile: TMetafile; Position: THPDFMetafilePosition; X, Y: Single) - Custom positioning
ShowMetafile(MetaFile: TMetafile; Options: THPDFEmfOptions) - Per-call rendering options
ShowMetafile(MetaFile: TMetafile; Position: THPDFMetafilePosition; X, Y: Single; Options: THPDFEmfOptions) - Position control with per-call rendering options
ShowMetafileEx(MetaFile: TMetafile; Options: THPDFEmfOptions) - direct page API with a one-draw EMF/WMF options override

Enhanced Processing Methods

EnhancedShowMetafile - Advanced processing with enhanced features
ShowEnhancedMetafile(Page, MetaFile, Options) - Global helper with per-call rendering options
ShowEnhancedMetafile(Page, MetaFile, Position, X, Y, Options) - Global helper with position control and per-call rendering options
ShowEnhancedMetafile(Page, FileName, Options) - File-name helper with per-call rendering options
ShowEnhancedMetafile(Page, FileName, Position, X, Y, Options) - File-name helper with position control and per-call rendering options
RenderEmfDirect - Direct EMF rendering for vector preservation
RenderEmfAsBitmap - Bitmap conversion for compatibility
RenderWmfAsBitmap - WMF bitmap rendering with position control

Technical Implementation

The enhanced EMF/WMF support is implemented through the HPDFEmf.pas unit, which provides:

THPDFEmfEnhanced: Core enhancement class for EMF processing
THPDFEmfPatcher: Utility class for EMF conversion and rendering
THPDFMetafilePosition: Enumeration for position control
Enhanced EMF Record Processing: Support for advanced EMF records

Advanced Features

EMF Record Support

EMR_BITBLT - Bitmap operations
EMR_STRETCHDIBITS - Stretched bitmap operations
EMR_ALPHABLEND - Alpha blending operations
Enhanced text rendering
Complex path operations

Rendering Options

Vector Preservation: Maintains vector graphics quality
Bitmap Fallback: Automatic fallback for complex graphics
Scaling Options: Automatic and manual scaling control
Quality Control: Configurable rendering quality settings
Canvas Layering: Set THPDFEmfOptions.CanvasOver when existing page content should paint above replayed Canvas metafile content
Redraw Control: Leave THPDFEmfOptions.Redraw enabled for the default temporary redraw path or disable it to parse the original metafile directly
Frame Clipping: Set THPDFEmfOptions.UseFrame to clip EMF output to the header frame when imported metafiles rely on frame bounds
Hatch Brush Patterns: EMF/WMF hatch brushes map to PDF tiling patterns so imported drawings keep their fill texture
Null Object Diagnostics: Keep null pens and null brushes invisible by default, or set THPDFEmfOptions.ShowNullPen and THPDFEmfOptions.ShowNullBrush when diagnostics need those paths or fills to become visible

Performance Optimizations

Memory-efficient processing for large metafiles
Optimized EMF record parsing
Intelligent caching for repeated elements
Reduced memory footprint during conversion

Compatibility and Standards

Windows EMF 1.0 and Enhanced EMF support
Windows Metafile (WMF) backward compatibility
Cross-platform rendering consistency
PDF vector graphics standards compliance

Troubleshooting

Common Issues and Solutions:

Large Metafiles: Use bitmap rendering for very large or complex metafiles
Text Rendering: Ensure fonts are available on the target system
Complex Graphics: Consider direct EMF rendering for better quality
Positioning Issues: Use custom positioning for precise placement

See Also