LMemoryFile::StartCompressBuffer

#include "ltwrappr.h"

virtual L_INT LMemoryFile::StartCompressBuffer(uInputBytes, uOutputBytes, nOutputType, nQFactor=2, pSaveFileOption=NULL)

L_UINT32 uInputBytes;	/* size of the user allocated buffer that will hold the raw data */
L_UINT uOutputBytes;	/* size of the user allocated compressed buffer */
L_INT nOutputType;	/* type of compression to use */
L_INT nQFactor;	/* quality factor */
pSAVEFILEOPTION pSaveFileOption;	/* pointer to optional extended save options */

Initializes the buffered compression engine. The compression is then carried out using the LMemoryFile::CompressBuffer function. It is ended by the LMemoryFile::EndCompressBuffer function.

Parameter	Description
uInputBytes	The size of user allocated buffer that will hold the raw data. This has to be a multiple of 8 lines or 16 lines depending on the output compression method specified. For LEAD1JTIF, LEAD1JFIF, or any LEAD Qfactor that is greater than 100, or a predefined setting of MC, SQT, or MCQ, you must allocate 16-line multiples. For all other compression factors and methods, manually set or predefined, 8-line multiples are required.
	To simplify your coding, you can always allocate 16-line multiples.
uOutputBytes	The size of user allocated compressed buffer.
nOutputType	Type of compression to use. Possible values are:
	Value	Meaning
	LEAD	[0] LEAD CMP compression format.
	JFIF	[1] JPEG File Interchange Format using YUV 4:4:4 color spacing.
	LEAD2JFIF	[5] JPEG File Interchange Format using YUV 4:2:2 color spacing.
	LEAD1JFIF	[3] JPEG File Interchange Format using YUV 4:1:1 color spacing.
	JTIF	[2] JPEG JTIF using YUV 4:4:4 color spacing.
	LEAD2JTIF	[6] JPEG JTIF using YUV 4:2:2 color spacing.
	LEAD1JTIF	[4] JPEG JTIF using YUV 4:1:1 color spacing.
nQFactor	Compression quality factor to use for the specified compression format. This value can be any integer ranging from 2 to 255 for all the supported compression methods.
	Alternatively, for LEAD CMP compression only, LEADTOOLS provides enhanced Q factors which are defined as follows:
	PQ1	[1] Perfect Quality compression Option 1.
	PQ2	[2] Perfect Quality compression Option 2.
	QFS	[3] Quality Far more important than Size.
	QMS	[4] Quality More important than Size.
	QS	[5] Quality and Size are equally important.
	SQS	[6] Size more important than Quality - Sharp.
	SQT	[7] Size more important than Quality - less Tilling.
	MCQ	[8] Maximum Compression, keeping quality as good as possible.
	MC	[9] Maximum Compression.
pSaveFileOption	Pointer to optional extended save options. Pass NULL to use the default save options.

Returns

SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

You must declare and initialize m_pBitmap calling this function, but you do not have to allocate the bitmap. In the bitmap handle, the Order field must be ORDER_BGR, and the ViewPerspective field must be TOP_LEFT. Then, the data that you put into the input buffer must be BGR and loaded from top left.

The compression process starts after the first call to LMemoryFile::CompressBuffer. You must override LMemoryFile::CompressBufferCallBack, which will be called when the output buffer is filled with compressed data or after completing the compression process. The callback function is responsible for emptying the output buffer — storing it, sending it, or doing other processing.

This function does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this function.

Required DLLs and Libraries

LTFIL
File format DLLs

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

See Also

Functions:	Class Members
Topics:	Raster Image Functions: Saving Files

Example

// define user LMemoryFile class to override its CallBacks
class LUserMemoryFile : public LMemoryFile
{
public:
   LUserMemoryFile () ;
   virtual ~LUserMemoryFile () ;
   virtual L_INT CompressBufferCallBack(LBitmapBase L_FAR* pLBitmap,
LBuffer L_FAR* pLBuffer);
};

LUserMemoryFile::LUserMemoryFile()
{

}

LUserMemoryFile::~LUserMemoryFile ()
{
}

L_INT LUserMemoryFile::CompressBufferCallBack(
                                LBitmapBase L_FAR* pLBitmap,
   LBuffer L_FAR* pLBuffer)
{
   MessageBox(NULL, TEXT("Here Compress Buffer CallBack"), TEXT("CompressBufferCallBack"), MB_OK);
   return SUCCESS ;
}

L_VOID TestCompBuff(LBitmapBase& LeadBitmap)
{
   LUserMemoryFile userLeadMemFile ;
   LBuffer LeadBuffer ;
   L_UINT uLineBytes ;
   L_INT i;

   userLeadMemFile.SetBitmap(&LeadBitmap) ;
   userLeadMemFile.EnableCallBack(TRUE) ;

   uLineBytes = LeadBitmap.GetWidth() * 3 ;

   // Initialize the compression engine
   userLeadMemFile.StartCompressBuffer(16 * uLineBytes,
                                       1024,
                                       LEAD,
                                       QFS,
                                       NULL);

   // Compress the data
   for( i = 0; i < LeadBitmap.GetHeight(); i++) // i is incremented at the end
   {
      // Get one line at time
      LeadBitmap.GetRow(&LeadBuffer, i);

      // This is the main function that will do the actual Compression.
      userLeadMemFile.CompressBuffer(&LeadBuffer);
   }

   // Reset the compression engine
   userLeadMemFile.EndCompressBuffer();
}