一、基本原理

1.BMP文件格式

BMP：Bitmap，位图格式，是一种Windows操作系统中的标准图像文件格式。它能够不做任何变换的存储图像像素域数据。通常可以分成设备相关位图（DDB）和设备无关位图（DIB）两类。由于它采用位映射存储格式，在绝大多数应用中不采用其他任何压缩，因此占用的空间也比其他突文件格式要大。BMP文件的图像深度可选1bit、4bit、8bit、16bit及24bit。

2.文件组成

组成部分	含义	字节数
位图文件头 BITMAPFILEHEADER	包含BMP图像文件类型、显示内容等	14
位图信息头 BITMAPINFOHEADER	包含BMP图像的压缩方式、颜色等信息	40
调色板 Palette	所包含的元素与位图所具有的颜色数相同，真彩色无调色板部分，灰度图像或索引图象有	4
实际数据 ImageData	真彩色图像：位图数据就是实际的RGB值灰度图像/索引图象：位图数据就是像素颜色再调色板中的索引值	4*n

位图文件头：

typedef struct tagBITMAPFILEHEADER {WORD bfType; 		/* 说明文件的类型 */DWORD bfSize; 		/* 说明文件的大小，用字节为单位 *//*注意此处的字节序问题WORD bfReserved1; 	/* 保留，设置为0 */WORD bfReserved2; 	/* 保留，设置为0 */DWORD bfOffBits; 	/* 说明从BITMAPFILEHEADER结构开始到实际的图像数据之间的字节偏移量 */} BITMAPFILEHEADER;

位图信息头：

typedef struct tagBITMAPINFOHEADER { DWORD biSize; 	/* 说明结构体所需字节数 */LONG biWidth; 	/* 以像素为单位说明图像的宽度 */LONG biHeight; 	/* 以像素为单位说明图像的高度*/WORD biPlanes; 	/* 说明位面数，必须为1 */WORD biBitCount; /* 说明位数/像素，1、2、4、8、24 */DWORD biCompression; /* 说明图像是否压缩及压缩类型BI_RGB，BI_RLE8，BI_RLE4，BI_BITFIELDS */DWORD biSizeImage; /* 以字节为单位说明图像大小 ，必须是4的整数倍*/LONG biXPelsPerMeter; /* 目标设备的水平分辨率，像素/米 */LONG biYPelsPerMeter; /*目标设备的垂直分辨率，像素/米 */DWORD biClrUsed; /* 说明图像实际用到的颜色数，如果为0则颜色数为2的biBitCount次方 */DWORD biClrImportant; /*说明对图像显示有重要影响的颜色索引的数目，如果是0，表示都重要。*/} BITMAPINFOHEADER;

调色板：

typedef struct tagRGBQUAD { BYTE rgbBlue; /*指定蓝色分量*/BYTE rgbGreen; /*指定绿色分量*/BYTE rgbRed; /*指定红色分量*/BYTE rgbReserved; /*保留，指定为0*/
} RGBQUAD;

位图数据：

从左到右、从上到下存放数据，每一扫描行的字节数必须是4的整数倍。

以上三个结构体在#<include> "windows.h" 中已经声明，使用时直接调用即可。

通常情况下由于信号动态范围大，会对信号做压缩处理，减小色差信号幅度，压缩后的色度信号变化动态范围更小，更适合传输。

Y = 0.299 R + 0.587 G + 0.114 B

R-Y = 0.701 R - 0.587 G - 0.114 B

B-Y = - 0.299 R - 0.587 G + 0.886 B

U = - 0.1684 R - 0.3316 G + 0.5 B + 128

V = 0.5 R - 0.4187 G - 0.0813 B + 128

二、实验思路

1.程序初始化（打开两个文件、定义变量和缓冲区等）

2.读取BMP文件，抽取或生成RGB数据写入缓冲区

3.调用RGB2YUV的函数实现RGB到YUV数据的转换

4.写YUV文件

5.关闭文件，释放缓冲区

三、代码实现

修改命令行参数

1.rgbtoyuv

rgb2yuv.h

#pragma once
#include<iostream>
using namespace std;void InitLookupTable();
int rgb2yuv(int x_dim, int y_dim, void* rgb, void* y_out, void* u_out, void* v_out, int flip);

main函数

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include "rgb2yuv.h"
using namespace std;#define u_int8_t	unsigned __int8
#define u_int		unsigned __int32
#define u_int32_t	unsigned __int32int main(int argc, char** argv)
{u_int Width = 256;u_int Height = 256;bool flip = true;u_int8_t* rgbBuf = NULL;u_int8_t* yBuf = NULL;u_int8_t* uBuf = NULL;u_int8_t* vBuf = NULL;u_int videoFramesWritten = 0;FILE* rgbFile = fopen("C:/Users/26617/Desktop/数据压缩/rgb5.rgb", "rb");FILE* yuvFile = fopen("C:/Users/26617/Desktop/数据压缩/out.yuv", "wb");// 输入缓冲区 rgbBuf = (u_int8_t*)malloc(Width * Height * 3);// 输出缓冲区 yBuf = (u_int8_t*)malloc(Width * Height);uBuf = (u_int8_t*)malloc((Width * Height) / 4);vBuf = (u_int8_t*)malloc((Width * Height) / 4);if (rgbBuf == NULL || yBuf == NULL || uBuf == NULL || vBuf == NULL){printf("error\n");exit(1);}while (fread(rgbBuf, 1, Width * Height * 3, rgbFile)){if (rgb2yuv(Width, Height, rgbBuf, yBuf, uBuf, vBuf, flip)){printf("error");return 0;}for (int i = 0; i < Width * Height; i++){// 亮度信号电平16-235 if (yBuf[i] < 16) yBuf[i] = 16;if (yBuf[i] > 235) yBuf[i] = 235;}for (int i = 0; i < Width * Height / 4; i++){// 色差信号电平16-240 if (uBuf[i] < 16) uBuf[i] = 16;if (uBuf[i] > 240) uBuf[i] = 240;if (vBuf[i] < 16) vBuf[i] = 16;if (vBuf[i] > 240) vBuf[i] = 240;}fwrite(yBuf, 1, Width * Height, yuvFile);fwrite(uBuf, 1, (Width * Height) / 4, yuvFile);fwrite(vBuf, 1, (Width * Height) / 4, yuvFile);}printf("the file is written\n");fclose(rgbFile);fclose(yuvFile);return(0);
}

rgb2yuv.cpp

#include "stdlib.h"
#include <iostream>
#include "rgb2yuv.h"static float RGBYUV02990[256], RGBYUV05870[256], RGBYUV01140[256];
static float RGBYUV01684[256], RGBYUV03316[256];
static float RGBYUV04187[256], RGBYUV00813[256];int rgb2yuv(int x_dim, int y_dim, void* rgb, void* y_out, void* u_out, void* v_out, int flip)
{static int init_done = 0;long i, j, size;unsigned char* r, * g, * b;unsigned char* y, * u, * v;unsigned char* pu1, * pu2, * pv1, * pv2, * psu, * psv;unsigned char* y_buffer, * u_buffer, * v_buffer;unsigned char* sub_u_buf, * sub_v_buf;if (init_done == 0){InitLookupTable();init_done = 1;}// 检查x_dim和y_dim能否被2整除 if ((x_dim % 2) || (y_dim % 2)) return 1;size = x_dim * y_dim;// 分配内存 y_buffer = (unsigned char*)y_out;sub_u_buf = (unsigned char*)u_out;sub_v_buf = (unsigned char*)v_out;u_buffer = (unsigned char*)malloc(size * sizeof(unsigned char));v_buffer = (unsigned char*)malloc(size * sizeof(unsigned char));if (!(u_buffer && v_buffer)){if (u_buffer) free(u_buffer);if (v_buffer) free(v_buffer);return 2;}b = (unsigned char*)rgb;y = y_buffer;u = u_buffer;v = v_buffer;// 将RGB转换为YUV if (!flip) {for (j = 0; j < y_dim; j++){y = y_buffer + (y_dim - j - 1) * x_dim;u = u_buffer + (y_dim - j - 1) * x_dim;v = v_buffer + (y_dim - j - 1) * x_dim;for (i = 0; i < x_dim; i++) {// RGB文件按 BGRBGR…顺序保存 g = b + 1;r = b + 2;// 按亮度方程转换，对色差信号引入压缩系数，进行归一化处理*y = (unsigned char)(RGBYUV02990[*r] + RGBYUV05870[*g] + RGBYUV01140[*b]);*u = (unsigned char)(-RGBYUV01684[*r] - RGBYUV03316[*g] + (*b) / 2 + 128);*v = (unsigned char)((*r) / 2 - RGBYUV04187[*g] - RGBYUV00813[*b] + 128);b += 3;y++;u++;v++;}}}else {for (i = 0; i < size; i++){// RGB文件按 BGRBGR…顺序保存 g = b + 1;r = b + 2;// 按亮度方程转换，对色差信号引入压缩系数，进行归一化处理 *y = (unsigned char)(RGBYUV02990[*r] + RGBYUV05870[*g] + RGBYUV01140[*b]);*u = (unsigned char)(-RGBYUV01684[*r] - RGBYUV03316[*g] + (*b) / 2 + 128);*v = (unsigned char)((*r) / 2 - RGBYUV04187[*g] - RGBYUV00813[*b] + 128);b += 3;y++;u++;v++;}}// 子样本 UV for (j = 0; j < y_dim / 2; j++){psu = sub_u_buf + j * x_dim / 2;psv = sub_v_buf + j * x_dim / 2;pu1 = u_buffer + 2 * j * x_dim;pu2 = u_buffer + (2 * j + 1) * x_dim;pv1 = v_buffer + 2 * j * x_dim;pv2 = v_buffer + (2 * j + 1) * x_dim;for (i = 0; i < x_dim / 2; i++){// 以正方形4个像素为单位共享1个uv，即进行下采样*psu = (*pu1 + *(pu1 + 1) + *pu2 + *(pu2 + 1)) / 4;*psv = (*pv1 + *(pv1 + 1) + *pv2 + *(pv2 + 1)) / 4;psu++;psv++;pu1 += 2;pu2 += 2;pv1 += 2;pv2 += 2;}}free(u_buffer);free(v_buffer);return 0;
}// 查找表函数 
void InitLookupTable()
{int i;for (i = 0; i < 256; i++) RGBYUV02990[i] = (float)0.2990 * i;for (i = 0; i < 256; i++) RGBYUV05870[i] = (float)0.5870 * i;for (i = 0; i < 256; i++) RGBYUV01140[i] = (float)0.1140 * i;for (i = 0; i < 256; i++) RGBYUV01684[i] = (float)0.1684 * i;for (i = 0; i < 256; i++) RGBYUV03316[i] = (float)0.3316 * i;for (i = 0; i < 256; i++) RGBYUV04187[i] = (float)0.4187 * i;for (i = 0; i < 256; i++) RGBYUV00813[i] = (float)0.0813 * i;
}

2.bmptoyuv

bmp2yuv.h

#pragma once
#include"stdio.h"
#include"windows.h"void read_bmp_2_get_rgb(FILE* bmp, unsigned char* rgb_out, BITMAPFILEHEADER& file_header, BITMAPINFOHEADER& info_header);
int RGB2YUV(int x_dim, int y_dim, void* bmp, void* y_out, void* u_out, void* v_out, int flip);
void InitLookupTable();

main函数

#include<windows.h>
#include<stdio.h>
#include "bmp2yuv.h"
#include<iostream>
using namespace std;
#define u_int8_t	unsigned __int8
#define u_int		unsigned __int32
#define u_int32_t	unsigned __int32int main(int argc, char** argv)
{int i = 0, k = 0;char bmp_name[7][20] = { "bmp1.bmp" ,"bmp2.bmp","bmp3.bmp","bmp4.bmp","bmp5.bmp" };FILE* yuvFile = fopen("out_video.yuv", "wb");BITMAPFILEHEADER File_header; // 文件头 BITMAPINFOHEADER Info_header; // 信息头 int frame_width, frame_height;for (k = 0; k < 5; k++){FILE* fp = fopen(bmp_name[k], "rb");if (fread(&File_header, sizeof(BITMAPFILEHEADER), 1, fp) != 1){cout << sizeof(BITMAPFILEHEADER) << endl;printf("read file header error!");exit(0);}// 位图文件头，判断是否为BMP文件 if (File_header.bfType != 0x4D42){printf("Not bmp file!");exit(0);}else{printf("this is a bmp file");}// 位图信息头，从中读取图片的宽、高、位数等信息 if (fread(&Info_header, sizeof(BITMAPINFOHEADER), 1, fp) != 1){printf("read info header error!");exit(0);}frame_width = Info_header.biWidth;frame_height = Info_header.biHeight;printf("\nThis is a %d bits image!\n", Info_header.biBitCount);printf("bmp size: \t%d X %d\n", Info_header.biWidth, Info_header.biHeight);printf("\n");u_int8_t* rgbBuf = NULL;u_int8_t* yBuf = NULL;u_int8_t* uBuf = NULL;u_int8_t* vBuf = NULL;yBuf = (u_int8_t*)malloc(frame_width * frame_height);uBuf = (u_int8_t*)malloc((frame_width * frame_height) / 4);vBuf = (u_int8_t*)malloc((frame_width * frame_height) / 4);rgbBuf = (u_int8_t*)malloc(frame_width * frame_height * 3);fseek(fp, File_header.bfOffBits, 0);fread(rgbBuf, frame_width * frame_height * 5, 1, fp);// 将BMP文件转为RGB文件 unsigned char* temp = new unsigned char[frame_width * frame_height * 5];unsigned char* temp1 = new unsigned char[frame_width * frame_height * 5];int  j = 256 * 256 * 5;for (i = 0; j >= 0; i += 5, j -= 5){*(temp + i) = *(rgbBuf + j - 3);*(temp + i + 1) = *(rgbBuf + j - 2);*(temp + i + 2) = *(rgbBuf + j - 1);}for (i = 0; i < 256; i++){for (j = 0; j < 256; j++){*(temp1 + 5 * j + i * 256 * 5) = *(temp + (255 - j) * 5 + i * 256 * 5);*(temp1 + 5 * j + 1 + i * 256 * 5) = *(temp + (255 - j) * 5 + 1 + i * 256 * 5);*(temp1 + 5 * j + 2 + i * 256 * 5) = *(temp + (255 - j) * 5 + 2 + i * 256 * 5);}}// 将转成的RGB文件再转为YUV文件 bool flip = true;rgb2yuv(frame_width, frame_height, temp1, yBuf, uBuf, vBuf, flip);//每张图片50帧，5张图片共250帧 j = 0;for (j = 0; j < 50; j++){fwrite(yBuf, 1, frame_width * frame_height, yuvFile);fwrite(uBuf, 1, (frame_width * frame_height) / 4, yuvFile);fwrite(vBuf, 1, (frame_width * frame_height) / 4, yuvFile);}}return 0;
}