opencv学习（二）

2022-05-30

将bmp图片转换成Base64字符串

方法：BmptoBase64
参数1(IN)：bmp文件路径(带文件名),eg: /tmp/tmp.bmp
参数2(OUT)：输出base64字符串

#include "opencv2/opencv.hpp"
#include "base64.h"
// LIBS += -lopencv_core -lopencv_imgcodecs
// g++ x.cpp -o x  -I*/opencv/include -L*/opencv/lib -lopencv_imgcodecs -lopencv_core
int BmptoBase64(const char *bmp_file, std::string &jeg_file)
{
    cv::Mat bmpimg = cv::imread(bmp_file);
    std::vector<uchar> image;
    std::vector<int> param;
	if (bmpimg.empty()) {
		return -1;
	}

	param.push_back(1);
	param.push_back(95);
	param.push_back(0);
	cv::imencode(".jpg", bmpimg, image, param);

    long size = image.size() * 2;
    char* base64 = new char[size];
	memset(base64, 0, size);
	Base64Encode(base64, (char *)(&image[0]), image.size());
	jeg_file = base64;
	delete [] base64;
}

Useage:

int main(int argc,char *argv[])
{
    const char *bmp_file = "tmp.bmp";
    std::string strbase64;
    BmptoBase64(bmp_file, strbase64);
    printf("BMP To Base64 done\r\n");
    printf("len: %d\r\n%s\r\n", strbase64.length(), strbase64.c_str());
 
    return 0;
}

附base64.h文件

////////////////////////////////////////////////////////////
// base64.h

// 参考文章：http://www.cstc.net.cn/docs/docs.php?id=202

//************************************************************************/
//    base64编码表
// 
//		0 A 17 R 34 i 51 z 
//		1 B 18 S 35 j 52 0 
//		2 C 19 T 36 k 53 1 
//		3 D 20 U 37 l 54 2 
//		4 E 21 V 38 m 55 3 
//		5 F 22 W 39 n 56 4 
//		6 G 23 X 40 o 57 5 
//		7 H 24 Y 41 p 58 6 
//		8 I 25 Z 42 q 59 7 
//		9 J 26 a 43 r 60 8 
//		10 K 27 b 44 s 61 9 
//		11 L 28 c 45 t 62 + 
//		12 M 29 d 46 u 63 / 
//		13 N 30 e 47 v (pad) = 
//		14 O 31 f 48 w 
//		15 P 32 g 49 x 
//		16 Q 33 h 50 y 
//
// base64编码步骤：
// 
//		原文：
//
//		你好
//		C4 E3 BA C3
//		11000100 11100011 10111010 11000011
//		00110001 00001110 00001110 00111010
//		49       14							（十进制）
//		x        O        O        6		字符
//		01111000 01001111 01001111 00110110
//		78									（十六进制）
//		xOO6
//
//		解码：
//		xOO6
//		78 4f 4f 36
//		01111000 01001111 01001111 00110110
//		49       14 
//		00110001 00001110 00001110 00111010   31 0e 0e 3a
//
//		11000100 11100011 10111010
//		C4       E3       BA
//

#ifndef _BASE64_INCLUDE__H__
#define _BASE64_INCLUDE__H__

// 编码后的长度一般比原文多占1/3的存储空间，请保证base64code有足够的空间
inline long Base64Encode(char * base64code, const char * src, long src_len); 
inline long Base64Decode(char * buf, const char * base64code, long src_len = 0);

__inline char GetB64Char(int index)
{
	const char szBase64Table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	if (index >= 0 && index < 64)
		return szBase64Table[index];
	
	return '=';
}

// 从双字中取单字节
#define B0(a) (a & 0xFF)
#define B1(a) (a >> 8 & 0xFF)
#define B2(a) (a >> 16 & 0xFF)
#define B3(a) (a >> 24 & 0xFF)

// 编码后的长度一般比原文多占1/3的存储空间，请保证base64code有足够的空间
inline long Base64Encode(char * base64code, const char * src, long src_len) 
{   
	if (src_len == 0)
		src_len = strlen(src);
	
	long len = 0;
	unsigned char* psrc = (unsigned char*)src;
	char * p64 = base64code;
	long i;
	for (i = 0; i < src_len - 3; i += 3)
	{
		unsigned long ulTmp = *(unsigned long*)psrc;
		register int b0 = GetB64Char((B0(ulTmp) >> 2) & 0x3F); 
		register int b1 = GetB64Char((B0(ulTmp) << 6 >> 2 | B1(ulTmp) >> 4) & 0x3F); 
		register int b2 = GetB64Char((B1(ulTmp) << 4 >> 2 | B2(ulTmp) >> 6) & 0x3F); 
		register int b3 = GetB64Char((B2(ulTmp) << 2 >> 2) & 0x3F); 
		*((unsigned long*)p64) = b0 | b1 << 8 | b2 << 16 | b3 << 24;
		len += 4;
		p64  += 4; 
		psrc += 3;
	}
	
	// 处理最后余下的不足3字节的饿数据
	if (i < src_len)
	{
		int rest = src_len - i;
		unsigned long ulTmp = 0;
		for (int j = 0; j < rest; ++j)
		{
			*(((unsigned char*)&ulTmp) + j) = *psrc++;
		}
		
		p64[0] = GetB64Char((B0(ulTmp) >> 2) & 0x3F); 
		p64[1] = GetB64Char((B0(ulTmp) << 6 >> 2 | B1(ulTmp) >> 4) & 0x3F); 
		p64[2] = rest > 1 ? GetB64Char((B1(ulTmp) << 4 >> 2 | B2(ulTmp) >> 6) & 0x3F) : '='; 
		p64[3] = rest > 2 ? GetB64Char((B2(ulTmp) << 2 >> 2) & 0x3F) : '='; 
		p64 += 4; 
		len += 4;
	}
	
	*p64 = '\0'; 
	
	return len;
}


__inline int GetB64Index(char ch)
{
	int index = -1;
	if (ch >= 'A' && ch <= 'Z')
	{
		index = ch - 'A';
	}
	else if (ch >= 'a' && ch <= 'z')
	{
		index = ch - 'a' + 26;
	}
	else if (ch >= '0' && ch <= '9')
	{
		index = ch - '0' + 52;
	}
	else if (ch == '+')
	{
		index = 62;
	}
	else if (ch == '/')
	{
		index = 63;
	}

	return index;
}

// 解码后的长度一般比原文少用占1/4的存储空间，请保证buf有足够的空间
inline long Base64Decode(char * buf, const char * base64code, long src_len) 
{   
	if (src_len == 0)
		src_len = strlen(base64code);

	long len = 0;
	unsigned char* psrc = (unsigned char*)base64code;
	char * pbuf = buf;
	long i;
	for (i = 0; i < src_len - 4; i += 4)
	{
		unsigned long ulTmp = *(unsigned long*)psrc;
		
		register int b0 = (GetB64Index((char)B0(ulTmp)) << 2 | GetB64Index((char)B1(ulTmp)) << 2 >> 6) & 0xFF;
		register int b1 = (GetB64Index((char)B1(ulTmp)) << 4 | GetB64Index((char)B2(ulTmp)) << 2 >> 4) & 0xFF;
		register int b2 = (GetB64Index((char)B2(ulTmp)) << 6 | GetB64Index((char)B3(ulTmp)) << 2 >> 2) & 0xFF;
		
		*((unsigned long*)pbuf) = b0 | b1 << 8 | b2 << 16;
		psrc  += 4; 
		pbuf += 3;
		len += 3;
	}

	// 处理最后余下的不足4字节的饿数据
	if (i < src_len)
	{
		int rest = src_len - i;
		unsigned long ulTmp = 0;
		for (int j = 0; j < rest; ++j)
		{
			*(((unsigned char*)&ulTmp) + j) = *psrc++;
		}
		
		register int b0 = (GetB64Index((char)B0(ulTmp)) << 2 | GetB64Index((char)B1(ulTmp)) << 2 >> 6) & 0xFF;
		*pbuf++ = b0;
		len  ++;

		if ('=' != B1(ulTmp) && '=' != B2(ulTmp))
		{
			register int b1 = (GetB64Index((char)B1(ulTmp)) << 4 | GetB64Index((char)B2(ulTmp)) << 2 >> 4) & 0xFF;
			*pbuf++ = b1;
			len  ++;
		}
		
		if ('=' != B2(ulTmp) && '=' != B3(ulTmp))
		{
			register int b2 = (GetB64Index((char)B2(ulTmp)) << 6 | GetB64Index((char)B3(ulTmp)) << 2 >> 2) & 0xFF;
			*pbuf++ = b2;
			len  ++;
		}

	}
		
	*pbuf = '\0'; 
	
	return len;
} 

#endif // #ifndef _BASE64_INCLUDE__H__