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

Summary

Initializes the buffered compression engine.

Syntax

C++/CLI

Java

Python

public void StartCompress( 
   int width, 
   int height, 
   int bitsPerPixel, 
   RasterByteOrder order, 
   RasterViewPerspective viewPerspective, 
   int inputDataLength, 
   byte[] outputData, 
   int outputDataIndex, 
   int outputDataLength, 
   CodecsCompression compression, 
   CodecsCompressDataCallback callback 
)

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)

public: 
void StartCompress(  
   int width, 
   int height, 
   int bitsPerPixel, 
   RasterByteOrder order, 
   RasterViewPerspective viewPerspective, 
   int inputDataLength, 
   array<byte>^ outputData, 
   int outputDataIndex, 
   int outputDataLength, 
   CodecsCompression compression, 
   CodecsCompressDataCallback^ callback 
)

def StartCompress(self,width,height,bitsPerPixel,order,viewPerspective,inputDataLength,outputData,outputDataIndex,outputDataLength,compression,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:

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

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, 
      CodecsCompressDataCallback); 
 
   // 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 CodecsCompressDataCallback(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:\LEADTOOLS23\Resources\Images"; 
}

Requirements

Target Platforms

Reference

RasterCodecs Class

RasterCodecs Members

Overload List

Compressing and Decompressing Buffers

Speeding Up 1-Bit Documents

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Help Version 23.0.2024.2.29