Guides

Image Compression Settings

CPDFOptimizeImageOption Parameter Description

The CPDFOptimizeImageOption class is used to configure detailed image compression parameters:

Property	Type	Default	Description
UperPpi	int	225	Upper PPI (pixels per inch), images above this value will be downsampled
TargetPpi	int	150	Target PPI, the target resolution after downsampling
CompAlg	CPDF_COMP_ALG	JPEG2000	Compression algorithm
Quality	int	40	Image quality (1-100)
BlockSize	int	256	Data block size (bytes)

CPDF_COMP_ALG Compression Algorithm Description

Algorithm	Value	Description	Use Case
COMP_ALG_JPEG2000	1	JPEG 2000 compression	High-quality color images, supports lossless and lossy compression
COMP_ALG_JPEG	2	Standard JPEG compression	Photos and color images, best compatibility
COMP_ALG_JBIG2	3	JBIG2 compression	Scanned documents and black-and-white images
COMP_ALG_CCITT4	4	CCITT Group 4 compression	Monochrome images, fax documents
COMP_ALG_CCITT3	5	CCITT Group 3 compression	Fax images, monochrome bitmaps

Configure Image Compression Options

// Create image optimization options
CPDFOptimizeImageOption imageOption = new CPDFOptimizeImageOption();
imageOption.UperPpi = 300;                              // Images above 300 PPI will be downsampled
imageOption.TargetPpi = 150;                            // Downsample target is 150 PPI
imageOption.CompAlg = CPDF_COMP_ALG.COMP_ALG_JPEG;      // Use JPEG compression
imageOption.Quality = 60;                               // Image quality 60%
imageOption.BlockSize = 256;                            // Block size 256 bytes

// Apply image options
optimizeOption.SetImageOption(imageOption);

// Get current image options
CPDFOptimizeImageOption currentImageOption = optimizeOption.GetImageOption();
Console.WriteLine($"Current compression algorithm: {currentImageOption.CompAlg}");
Console.WriteLine($"Current image quality: {currentImageOption.Quality}");

Quick Set Image Quality

If you only need to adjust image quality, you can use the shortcut method:

// Set image quality (1-100)
optimizeOption.SetImageQuality(75.0f);

// Get current image quality
float quality = optimizeOption.GetImageQuality();
Console.WriteLine($"Current image quality: {quality}");