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StartCompress(int,int,int,RasterByteOrder,RasterViewPerspective,int,byte[],int,int,CodecsCompression,CodecsCompressDataCallback) Method

Summary
Initializes the buffered compression engine.
Syntax
C#
VB
C++
Java
Public Overloads Sub StartCompress( _ 
   ByVal width As Integer, _ 
   ByVal height As Integer, _ 
   ByVal bitsPerPixel As Integer, _ 
   ByVal order As RasterByteOrder, _ 
   ByVal viewPerspective As RasterViewPerspective, _ 
   ByVal inputDataLength As Integer, _ 
   ByVal outputData() As Byte, _ 
   ByVal outputDataIndex As Integer, _ 
   ByVal outputDataLength As Integer, _ 
   ByVal compression As CodecsCompression, _ 
   ByVal callback As CodecsCompressDataCallback _ 
)  
public void startCompress( 
   int width,  
   int height,  
   int bitsPerPixel,  
   RasterByteOrder order,  
   RasterViewPerspective viewPerspective,  
   int inputDataLength,  
   byte[] outputData,  
   int outputDataIndex,  
   int outputDataLength,  
   CodecsCompression compression,  
   CodecsCompressDataListener callback) 

Parameters

width
The image being compressed width in pixels.

height
The image being compressed height in pixels.

bitsPerPixel
The image being compressed bits/pixel value.

order
The image being compressed byte order.

viewPerspective
The image being compressed view perspective value.

inputDataLength
Size in bytes of the input image data.

outputData
Array of bytes which will be filled with the compressed data.

outputDataIndex
Index into outputData where the compressed data should be inserted.

outputDataLength
Size of outputData in bytes.

compression
Type of compression to use. Valid values are:

Value Meaning
CodecsCompression.Cmp LEAD CMP compression format
CodecsCompression.Jpeg444 JPEG File Interchange Format using YUV 4:4:4 color spacing
CodecsCompression.Jpeg422 JPEG File Interchange Format using YUV 4:2:2 color spacing
CodecsCompression.Jpeg411 JPEG File Interchange Format using YUV 4:1:1 color spacing
CodecsCompression.TifJpeg444 JPEG JTIF using YUV 4:4:4 color spacing
CodecsCompression.TifJpeg422 JPEG JTIF using YUV 4:2:2 color spacing
CodecsCompression.TifJpeg411 JPEG JTIF using YUV 4:1:1 color spacing
CodecsCompression.Lead0 LEAD 1 bit, lossless compression
CodecsCompression.Lead1 LEAD 1 bit, excellent compression
CodecsCompression.TiffCcitt TIFF CCITT
CodecsCompression.TiffCcittG3Fax1Dim CCITT Group 3 one dimensional
CodecsCompression.TiffCcittG3Fax2Dim CCITT Group 3 two dimensional
CodecsCompression.TiffCcittG4Fax CCITT Group 4 two dimensional

callback
The callback method responsible for writing or handling the compressed data.

Remarks

This method initializes the buffered compression engine. The compression is then carried out using the Compress method. It is ended by the StopCompress method.

If order is set to RasterByteOrder.Bgr and viewPerspective is RasterViewPerspective.TopLeft then the data that you put into the input buffer must be RasterByteOrder.Bgr and loaded from top left.

The compression process starts after the first call to Compress. The callback is called when the output buffer is filled with compressed data or after completing the compression process. callback is responsible for emptying the output buffer - storing it, sending it, or doing other processing.

The following is a flow chart that shows the relationship of these methods:

compressbuffer.gif

Call StopCompress to end the compression process started by a call to StartCompress.

The quality factor of the compressed data is obtained as follows:

Format Quality factor used
CodecsCompression.Cmp CodecsJpegSaveOptions.QualityFactor and CodecsJpegSaveOptions.CmpQualityFactorPredefined
CodecsCompression.Jpeg444 CodecsJpegSaveOptions.QualityFactor
CodecsCompression.Jpeg422 CodecsJpegSaveOptions.QualityFactor
CodecsCompression.Jpeg411 CodecsJpegSaveOptions.QualityFactor
CodecsCompression.TifJpeg444 CodecsJpegSaveOptions.QualityFactor
CodecsCompression.TifJpeg422 CodecsJpegSaveOptions.QualityFactor
CodecsCompression.TifJpeg411 CodecsJpegSaveOptions.QualityFactor
CodecsCompression.Lead0 Not used
CodecsCompression.Lead1 Not used
CodecsCompression.TiffCcitt Not used
CodecsCompression.TiffCcittG3Fax1Dim Not used
CodecsCompression.TiffCcittG3Fax2Dim Not used
CodecsCompression.TiffCcittG4Fax Not used

This method does not support signed data images.

Example

This example demonstrates low-level image compression using StartCompress, Compress and StopCompress. The callback method for writing the output is included at the end of the example

C#
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Svg; 
 
 
public void CompressExample() 
{ 
	RasterCodecs codecs = new RasterCodecs(); 
 
	string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp"); 
	string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1_CompressData.cmp"); 
 
	// Load the image to at 24-bits per pixel 
	RasterImage image = codecs.Load(srcFileName, 24, CodecsLoadByteOrder.Bgr, 1, 1); 
	if (image.ViewPerspective != RasterViewPerspective.TopLeft) 
		image.ChangeViewPerspective(RasterViewPerspective.TopLeft); 
 
	// Create the output file 
	_compressStream = File.Create(destFileName); 
 
	// Calculate the bytes per line in the input buffer, without padding  
	int lineBytes = image.Width * 3; 
 
	// Allocate a buffer for the incoming uncompressed data. Note that we 
	//  are compressing 16 lines at a time. You should always use multiples of 16 
	byte[] inBuffer = new byte[16 * lineBytes]; 
 
	// Allocate an output buffer. This is where the compressed data will 
	// go.  Note that this allocates 1024-byte packets.  
	byte[] outBuffer = new byte[1024]; 
 
	// Lock down the image 
	image.Access(); 
 
	// Initialize the compression engine 
	codecs.Options.Jpeg.Save.CmpQualityFactorPredefined = CodecsCmpQualityFactorPredefined.QualityAndSize; 
	codecs.StartCompress( 
	   image.Width, 
	   image.Height, 
	   image.BitsPerPixel, 
	   image.Order, 
	   image.ViewPerspective, 
	   16 * lineBytes, 
	   outBuffer, 
	   0, 
	   outBuffer.Length, 
	   CodecsCompression.Cmp, 
	   MyCodecsCompressDataCallback); 
 
	// Compress the data 
	int i = 0; 
	while (i < image.Height) // i is incremented at the end 
	{ 
		// Compression of the 16-line chunk starts here 
		int j = 0; 
		int inBufferIndex = 0; 
		while ((i + j) < image.Height && j < 16) 
		{ 
			// Get one line at time 
			image.GetRow(i + j, inBuffer, inBufferIndex, lineBytes); 
 
			// Move to next line 
			inBufferIndex += lineBytes; 
 
			j++; 
		} 
 
		// This is the main function that will do the actual Compression 
		codecs.Compress(inBuffer, 0); 
		i += 16; 
	} 
 
	// Reset the compression engine  
	codecs.StopCompress(); 
 
	// Release the image and close the file 
	image.Release(); 
	_compressStream.Close(); 
 
	// Clean up 
	codecs.Dispose(); 
} 
 
FileStream _compressStream; 
byte[] _compressBuffer; 
 
bool MyCodecsCompressDataCallback(int width, int height, int bitsPerPixel, RasterByteOrder order, RasterViewPerspective viewPerspective, RasterNativeBuffer buffer) 
{ 
	// Write data to the file 
	if (_compressBuffer == null || _compressBuffer.Length < buffer.Length) 
		_compressBuffer = new byte[(int)buffer.Length]; 
 
	Marshal.Copy(buffer.Data, _compressBuffer, 0, (int)buffer.Length); 
 
	_compressStream.Write(_compressBuffer, 0, (int)buffer.Length); 
 
	return true; 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS21\Resources\Images"; 
} 
Requirements

Target Platforms

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Leadtools.Codecs Assembly