RGB与YUV的互相转换

RGB与YUV的互相转换

一、实验目的：完成彩色空间的互相转换，即将.yuv图片转换为.rgb图片，将.rgb图片转换为.yuv文件。

先调试老师给出的.rgb文件转换至.yuv文件代码，理清思路，再写出.yuv文件转换至.rgb文件代码。

down.yuv（需转换的yuv文件）图片如上，其采样格式为4：2：0，分辨率为256×256.

down.rgb（需转换的rgb文件）图片如上，格式为RGB24，分辨率为256×256.

二、前导知识

1.转换公式
Y = 0.2990R + 0.5870G + 0.1140B;

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

V = 0.5R - 0.4187G - 0.083B + 128;

R = Y + 1.4075( V - 128);

G = Y - 0.3455( U - 128) - 0.7169( V - 128);

B = Y + 1.779( U - 128);
2.存储格式
.yuv文件先存y再存uv，.rgb文件bgr顺序存储（4：4：4）即bgrbgr…
3.采样
因为yuv文件采样格式为4:2:0，所以将.rgb文件转换为.yuv文件时要进行下采样，.yuv文件转换为.rgb文件时要进行上采样.

三、代码

1.rgbtoyuv
rgb2yuv.h

int RGB2YUV (int x_dim, int y_dim, void *bmp, void *y_out, void *u_out, void *v_out, int flip);

void InitLookupTable();

main.cpp

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include "rgb2yuv.h"

#define u_int8_t	unsigned __int8
#define u_int		unsigned __int32
#define u_int32_t	unsigned __int32
#define FALSE		false
#define TRUE		true

/*
 * rgb2yuv
 * required arg1 should be the input RAW RGB24 file
 * required arg2 should be the output RAW YUV12 file
 */ 
int main(int argc, char** argv)
{
   
	/* variables controlable from command line */
	u_int frameWidth = 352;			/* --width=<uint> */
	u_int frameHeight = 240;		/* --height=<uint> */
	bool flip = TRUE;				/* --flip */
	unsigned int i;

	/* internal variables */
	char* rgbFileName = NULL;
	char* yuvFileName = NULL;
	FILE* rgbFile = NULL;
	FILE* yuvFile = NULL;
	u_int8_t* rgbBuf = NULL;
	u_int8_t* yBuf = NULL;
	u_int8_t* uBuf = NULL;
	u_int8_t* vBuf = NULL;
	u_int32_t videoFramesWritten = 0;

	/* begin process command line */
	/* point to the specified file names */
	rgbFileName = argv[1];
	yuvFileName = argv[2];

	frameWidth = atoi(argv[3]);
	frameHeight = atoi(argv[4]);
	
	/* open the RGB file */
	rgbFile = fopen(rgbFileName,"rb");
	if (rgbFile == NULL)
	{
   
		printf("cannot find rgb file\n");
		exit(1);
	}
	else
	{
   
		printf("The input rgb file is %s\n", rgbFileName);
	}

	/* open the RAW file */
	yuvFile = fopen(yuvFileName, "wb");
	if (yuvFile == NULL)
	{
   
		printf("cannot find yuv file\n");
		exit(1);
	}
	else
	{
   
		printf("The output yuv file is %s\n", yuvFileName);
	}

	/* get an input buffer for a frame */
	rgbBuf = (u_int8_t*)malloc(frameWidth * frameHeight * 3);

	/* get the output buffers for a frame */
	yBuf = (u_int8_t*)malloc(frameWidth * frameHeight);
	uBuf = (u_int8_t*)malloc((frameWidth * frameHeight) / 4);
	vBuf = (u_int8_t*)malloc((frameWidth * frameHeight) / 4);

	if (rgbBuf == NULL || yBuf == NULL || uBuf == NULL || vBuf == NULL)
	{
   
		printf("no enought memory\n");
		exit(1);
	}

	while (fread(rgbBuf, 1, frameWidth * frameHeight * 3, rgbFile)) 
	{
   
		if(RGB2YUV(frameWidth, frameHeight, rgbBuf, yBuf, uBuf, vBuf, flip))
		{
   
			printf("error");
			return 0;
					}

		for (i = 0; i < frameWidth*frameHeight; i++)
		{
   
			if (yBuf[i] < 16) yBuf[i] = 16;
			if (yBuf[i] > 235) yBuf[i] = 235;
		}

		for (i = 0; i < frameWidth*frameHeight/4; i++)
		{
   
			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