encoder.cpp

基于块方向的图像无损压缩代码

#include "stdafx.h"
#include "globals.h"
#include "prototypes.h"
#include "marker.h"
#include "read_write.h"
#define BLOCK 32

void EncodingImage(short int **ImageData,PBYTE DirectionBlock[BLOCK*2],long width,long height,CString OutFile)
{
	extern char  **dim2(int nr,int nc,unsigned size);
	int 		i,j;
	int         tmp;

	dim.x=height;
	dim.y=width;
	
	P = 8;//一个像素点用8位来表示
 
	pdim.x = dim.x+1;
	pdim.y = dim.y+2;

	/* set the encoding parameters based on precision value */
	if(P<=8)
	{
		T1 = 3;
		T2 = 7;
		T3 = 21;
	}
	else 
	{
		T1 = 18;
		T2 = 67;
		T3 = 276;
	}
	
	MAXVAL = (int)(pow(2.0,P)-1);
//	fprintf(stderr,"Precision = %d, MAXVAL = %d\n", P, MAXVAL);
 
	 /* Write Header Information */
 
	ofp = fopen(OutFile,"wb");
	WriteSoi();
	WriteSof();
	WriteSos();
 
	in_buf = (int **) dim2(pdim.x,pdim.y,sizeof(int));//申请2维指针
	
	//将ImageData中的数据传给in_buf，注意in_buf和ImageData的大小不一（长宽）
	//in_buf中第0行、第0列和最后一列数据为0（未赋值）
	GetData(ImageData,dim.x,dim.y,in_buf);
 
	/* initialize the boundary conditions */
 
	for(j=0; j<pdim.y; j++)
		in_buf[0][j] = 0;  //第0行数据为0
	for(i=1; i<pdim.x; i++)
	{
		in_buf[i][0] = in_buf[i-1][1];//第0列数据与第1列数据相等
		in_buf[i][pdim.y-1] = in_buf[i][pdim.y-2];//最后1列数据与倒数第2列数据相等
	}
 
	/*  RANGE = (int)((MAXVAL+2*NEAR)/(2*NEAR+1))+1; */
	RANGE = MAXVAL + 1;

	/* updated variable */
	qbpp =  (int)(log(RANGE)/(log(2.0)));
	bpp  = MAX(2,(int)(log(MAXVAL+1)/log(2.0)));
	LIMIT = 2*(bpp+MAX(8,bpp));
 
	/* initialaize some variables */
	tmp = MAX(2,(int)((RANGE+32)/64));
	for(i=0; i< 365; i++)
	{
		A[i] = tmp;
		N[i] = 1;
		B[i] = 0;
		Nn[i] = 0;
		C[i] = 0;
	}
	A[365] = tmp;
	A[366] = tmp;
	N[365] = 1;
	N[366] = 1;
	RUNindex = 0;
	Nn[365] = 0;
	Nn[366] = 0;
	x.x = 1;
	x.y = 0;
	count = 0;
	EOLine = 0;
	current_write_byte = 0;
	write_position = 7;
 
	for(;;)
	{
 		if(count == dim.x*dim.y )
			break;
 		
		GetNextSample();
		D[0] = Rd - Rb;
		D[1] = Rb - Rc;
		D[2] = Rc - Ra;
 
		if (D[0] == 0 && D[1] == 0 && D[2] == 0)
			RunModeProcessing();
		else
			RegularModeProcessing();
	}
 
	if(write_position < 7)
		putc(current_write_byte, ofp);
	WriteEoi();
	fclose(ofp);
}
 
/**************************************************************
AppendToBitStream() puts n bits from b onto the writer stream.
**************************************************************/
 
void AppendToBitStream(int b,int n)
{
 
	if((b>>n) > 0 || b < 0)
	{
		fprintf(stderr,"Error: %d Bits are not enough to represent the number %d\n", n, b);
		exit(0);
	}
 
	while(n--)
	{
		if(b&bit_set_mask[n]) 
		{
			mput1();
		}
		else 
		{
			mput0();
		}
	}
}