c jpeg 理论霍夫曼 DC AC表，c程序实现正向逆向转换

此4张表是理论表，不是针对某张图片的特定表。如编码程序不统计生成某图片的专用霍夫曼表，应该也可用理论表代用编码。

1.亮度DC表

左边第一列是二进制位数，就是对此位数编码

中间一列是生成比特流的位数，右边是生成的比特流。

2.色度DC表

3.亮度AC表

4.? 色度AC表

?利用这4张表转换生成亮度，色度的DC，AC比特流

图3图4两张表是用jpeg文件头的形式显示的。

AC 表被编码的数值是两部分组成的，高4比特是0的个数 （a,b）对中的a，低4节为b的二进制位数。

两个AC表中的162个数就是两个输入参数组成的一个字节的值。

对于DC表，直接用if一一例举出现就行了。AC两张表输出都是162个数，这162个数的比特流从1位到16位都有。

? 看了AC两张表，最多的是16位的比特流。

AC表的输入为0的个数和二进制位数两个参数，输出为比特流和比特流宽度。

--------------------------------

亮度AC表：

2 位：2个? ? ?00(1)?，01(2)

3位：1? ? ? 010(0),

4位：3? ? ? 0110(4)，0111(11), 1000(5)

5位：3? ? ?10010(12) ,10011(21),10100(31)

6位：2? ? ?101010(41), 101011(6)

7位：4? ? ? 1011000(13),1011001(51), 1011010(61),1011011(7)

8位：3? ? ? ? 10111000(22),? 10111001(71),? 10111010(14)

9位：5? ? ? ? 101110110(32),? 101110111(81), 101111000(91)? ，101111001(A1), 101111010(8)

10位：5? ? ? 1011110110(23),? ? ? ? ? ?1011110111(42),1011111000(b1),?1011111001(c1),1011111010(15)

11位：4? ? ?10111110110(52),? ?10111110111(d1),? 10111111000(f0), 10111111001(24)

12位：4? ? ?101111110100(33),? ?101111110101(62), 101111110110(72),101111110111(82)

15位：1? ? ?101111111000000(9),

16位 ：125? ? ?1011111110000010(0a),，，，，，，

共计162个

亮度AC转换：本想用查表法代码太长了，162个if语句。现还不包括16位的数据转换，准备换一种方法。DC可以用这种方法。

?1. 亮度AC编码用正向程序

?
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>  
#include <string.h>
#include <sys/mman.h>
#include <linux/fb.h>
#include <math.h>

int main(void) {
	unsigned char i_0=0xf;
	unsigned char i_len=0xa;
	
	unsigned char len;
	unsigned int o;
	
	unsigned char zj=i_0*16+i_len;      //合成一个字节
	
	unsigned char  ws[16]={0,2,1,3,3,2,4,3,5,5,4,4,0,0,1,0x7d};
	unsigned char zh[162]={0x1, 0x2, 0x3, 0x0, 0x4, 0x11, 0x5,0x12,0x21,0x31,0x41,0x6, 0x13,0x51,0x61,0x7,
		                   0x22,0x71,0x14,0x32,0x81,0x91,0xa1,0x08,0x23,0x42,0xb1,0xc1,0x15,0x52,0xd1,0xf0,
		                   0x24,0x33,0x62,0x72,0x82,0x09,0x0a,0x16,0x17,0x18,0x19,0x1a,0x25,0x26,0x27,0x28,
	                    	0x29,0x2a,0x34,0x35,0x36,0x37,0x38,0x39,0x3a,0x43,0x44,0x45,0x46,0x47,0x48,0x49,
		0x4a,0x53,0x54,0x55,0x56,0x57,0x58,0x59,0x5a,0x63,0x64,0x65,0x66,0x67,0x68,0x69,
		0x6a,0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7a,0x83,0x84,0x85,0x86,0x87,0x88,0x89,
		0x8a,0x92,0x93,0x94,0x95,0x96,0x97,0x98,0x99,0x9a,0xa2,0xa3,0xa4,0xa5,0xa6,0xa7,
		0xa8,0xa9,0xaa,0xb2,0xb3,0xb4,0xb5,0xb6,0xb7,0xb8,0xb9,0xba,0xc2,0xc3,0xc4,0xc5,
		0xc6,0xc7,0xc8,0xc9,0xca,0xd2,0xd3,0xd4,0xd5,0xd6,0xd7,0xd8,0xd9,0xda,0xe1,0xe2,
		0xe3,0xe4,0xe5,0xe6,0xe6,0xe7,0xe8,0xe9,0xea,0xf1,0xf2,0xf3,0xf4,0xf5,0xf6,0xf7,
		0xf9,0xfa
	};
	int cx_ws,cx_b;
	unsigned char hfm[17][0x7d]={};
	int t=0;
	for(int a=0;a<16;a++){             //把要编码的162个数按位数分为16个数组，二位一组....16位一组
		if(ws[a]==0){
			continue;
		}
		
		for(int b=0;b<ws[a];b++){
			hfm[a+1][b]=zh[t];
			t++;
		}
	}
	for(int a=0;a<16;a++){               //查询输入数的位数和在所在组的顺序，组内顺序从0开始
		if(ws[a]==0){
			continue;
		}
		
		for(int b=0;b<ws[a];b++){
			if(	hfm[a+1][b]==zj){
				cx_ws=a+1;         //得到输入数二进制位数，根据此数到相依位数的数组查询
				cx_b=b;            //输入数在按位数分组的数组中所在的位置，从0开始
				break;
			}
		}
	}

	int o_js=0;       //每一组的第一个数的值
	if(cx_ws==2){
		o_js=0;
	}
	if(cx_ws==3){
		o_js=0b010;
	}
	if(cx_ws==4){
		o_js=0b0110;
	}
	if(cx_ws==5){
		o_js=0b10010;
	}
	if(cx_ws==6){
		o_js=0b101010;
	}
	if(cx_ws==7){
		o_js=0b1011000;
	}
	if(cx_ws==8){
		o_js=0b10111000;
	}
	if(cx_ws==9){
		o_js=0b101110110;
	}
	if(cx_ws==10){
		o_js=0b1011110110;
	}
	if(cx_ws==11){
		o_js=0b10111110110;
	}
	if(cx_ws==12){
		o_js=0b101111110100;
	}
	if(cx_ws==15){
		o_js=0b101111111000000;
	}
	if(cx_ws==16){
		o_js=0b1011111110000010;
	}
	len=cx_ws;
	o=o_js+cx_b;
	printf("len:%d o:%d\n",len,o);
	
	return 0;	
}

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2.亮度AC 解码程序

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>  
#include <string.h>
#include <sys/mman.h>
#include <linux/fb.h>
#include <math.h>

int main(void) {
	unsigned int i_bit=0b1011111110000011;
	unsigned char i_len=16;
	
	unsigned char len;
	unsigned char o;
	
	unsigned char  ws[16]={0,2,1,3,3,2,4,3,5,5,4,4,0,0,1,0x7d};
	unsigned char zh[162]={0x1, 0x2, 0x3, 0x0, 0x4, 0x11, 0x5,0x12,0x21,0x31,0x41,0x6, 0x13,0x51,0x61,0x7,
		0x22,0x71,0x14,0x32,0x81,0x91,0xa1,0x08,0x23,0x42,0xb1,0xc1,0x15,0x52,0xd1,0xf0,
		0x24,0x33,0x62,0x72,0x82,0x09,0x0a,0x16,0x17,0x18,0x19,0x1a,0x25,0x26,0x27,0x28,
		0x29,0x2a,0x34,0x35,0x36,0x37,0x38,0x39,0x3a,0x43,0x44,0x45,0x46,0x47,0x48,0x49,
		0x4a,0x53,0x54,0x55,0x56,0x57,0x58,0x59,0x5a,0x63,0x64,0x65,0x66,0x67,0x68,0x69,
		0x6a,0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7a,0x83,0x84,0x85,0x86,0x87,0x88,0x89,
		0x8a,0x92,0x93,0x94,0x95,0x96,0x97,0x98,0x99,0x9a,0xa2,0xa3,0xa4,0xa5,0xa6,0xa7,
		0xa8,0xa9,0xaa,0xb2,0xb3,0xb4,0xb5,0xb6,0xb7,0xb8,0xb9,0xba,0xc2,0xc3,0xc4,0xc5,
		0xc6,0xc7,0xc8,0xc9,0xca,0xd2,0xd3,0xd4,0xd5,0xd6,0xd7,0xd8,0xd9,0xda,0xe1,0xe2,
		0xe3,0xe4,0xe5,0xe6,0xe6,0xe7,0xe8,0xe9,0xea,0xf1,0xf2,0xf3,0xf4,0xf5,0xf6,0xf7,
		0xf9,0xfa
	};
	unsigned char  cx_ws,cx_b;
	
	unsigned char hfm[17][0x7d]={};
	int t=0;
	for(int a=0;a<16;a++){             
		if(ws[a]==0){
			continue;
		}
		
		for(int b=0;b<ws[a];b++){
			hfm[a+1][b]=zh[t];
			t++;
		}
	}
//---------------------------------------
	cx_ws=i_len;
	
	int o_js=0;      
	if(cx_ws==2){
		o_js=0;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==3){
		o_js=0b010;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==4){
		o_js=0b0110;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==5){
		o_js=0b10010;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==6){
		o_js=0b101010;
		cx_b=i_bit-o_js;	
	}
	if(cx_ws==7){
		o_js=0b1011000;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==8){
		o_js=0b10111000;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==9){
		o_js=0b101110110;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==10){
		o_js=0b1011110110;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==11){
		o_js=0b10111110110;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==12){
		o_js=0b101111110100;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==15){
		o_js=0b101111111000000;
		cx_b=i_bit-o_js;
	}
	if(cx_ws==16){
		o_js=0b1011111110000010;
		cx_b=i_bit-o_js;
	}
	
//-----------------------------------------

	unsigned char o_zj=hfm[cx_ws][cx_b];

	len=o_zj/16;
	o=o_zj%16;
	
	printf("%x  %x",len,o);
	return 0;	
}

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