ImageMan.Net Version 3 Summer 2012 Release
PdfCompression Enumeration
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DTI.ImageMan.Codecs Namespace : PdfCompression Enumeration





Glossary Item Box

PdfCompression Method for Pdf Document

Syntax

Visual Basic (Declaration) 
Public Enum PdfCompression 
   Inherits System.Enum
Visual Basic (Usage)Copy Code
Dim instance As PdfCompression
C# 
public enum PdfCompression : System.Enum 
JScript 
public enum PdfCompression extends System.Enum
Managed Extensions for C++ 
__value public enum PdfCompression : public System.Enum 
C++/CLI 
public enum class PdfCompression : public System.Enum 

Members

MemberDescription
DefaultPdfCompression

Will choose the best default option based on color depth. CCITTFax4Decode for monochrome images, JPEG compression for 24 bit, and FLATE for all others.

Supported BitDepths2,4,8,24.

PdfCCITTFax3Decode

CCITT Group 3 compression is the standard in fax communications.

Supported BitDepths2.

PdfCCITTFax4Decode

CCITT Group 4 compression is a two dimensional compression method. And is one of the best for black and white images that have around 5-10% coverage and are mainly text or line art.

Supported BitDepth 2.

PdfFLATE

FLATE or PNG compression is probably the best choice if you need to pick one compression method for all color depths. It is also the best choice if you need lossless compression for 24 bit images. Flate compression has support for the standard PNG filters using the FlateFilter:PdfEncoder: property. As well as the ability to specify the amount of compression using the FlateCompressionLevel:PdfEncoder: property on a level from 1 to 9, 9 is the highest compression, 8 is the default.

Supported BitDepths2,4,8,24.

PdfJPG

JPEG encoding is an excellent choice for photographs or computer rendered images. It is lossy and therefore even though it has excellent compression some loss of information can happen, especially when two colors of sharp contrast form a sharp line, there can be some artifacts or haloing in the adjacent pixels. The PdfEncoder property lets you specify the compression from 1 to 99 with 99 being the highest image quality, 75 is the default.

In order for an image to be saved in grayscale format it must have a ramped palette. A ramped palette is created when the ImageMan Palette is created using the GrayScale PaletteType:DTI::ImageMan::ImPalette::PaletteType:.

PdfLZWDecode

LZW decoding provides excellent compression for images with palettes including black and white images that have higher coverage, and color images made up of either text or graphics. Our implementation of LZW also includes a predictor which yields reasonable lossless compression for 24 bit color images as well.

Supported BitDepths2,4,8,24.

PdfRunLengthDecode

Run Length Encoding or RLE is not optimal and can lead to larger images than ones that are not compressed at all in worst case scenarios.

Supported BitDepth 2.

Remarks

The following compression methods are supported by the PDF Exporter by setting the PdfCompression:PdfEncoder: property to any of the following options.

Inheritance Hierarchy

System.Object
   System.ValueType
      System.Enum
         DTI.ImageMan.Codecs.PdfCompression

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

See Also

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