图像基础：读取BMP图片，转换为RGB与YU12（YUV420P）格式，同时YU12、NV12、NV21之间相互转换BMP转RGBRGB转YU12（YUV420P）YU12转NV12YU12转NV21NV12转YU12NV21转YU12完整工程代码下载链接：

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我是靠谱客的博主积极发夹，最近开发中收集的这篇文章主要介绍图像基础：读取BMP图片，转换为RGB与YU12（YUV420P）格式，同时YU12、NV12、NV21之间相互转换BMP转RGBRGB转YU12（YUV420P）YU12转NV12YU12转NV21NV12转YU12NV21转YU12完整工程代码下载链接：，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

BMP转RGB

//输入：1、申请的RGB内存
//	   2、打开的BMP文件
void ReadBmp(unsigned char *RGB, FILE *fp)
{
	int i, j;
	unsigned char temp;

	//int fseek(FILE *stream, long offset, int fromwhere);
	//指向以fromwhere为基准，偏移offset（指针偏移量）个字节的位置，函数返回0
	//因为已知格式信息：分辨率为640*480	色深为24bit		
	//功能：跳过头文件
	fseek(fp, 54, SEEK_SET);

	//size_t fread( void *buffer, size_t size, size_t count, FILE *stream );
	//buffer	指向要读取的数组中首个对象的指针
	//size		每个对象的大小（单位是字节）
	//count		要读取的对象个数
	//stream	输入流
	//功能：将整个数据存储到RGB内存中的后半段中
	fread(RGB + WIDTH*HEIGHT * 3, 1, WIDTH*HEIGHT * 3, fp);//读取

	//功能：将RGB前半段按顺序填充
	for (i = HEIGHT - 1, j = 0; i >= 0; i--, j++)//调整顺序
	{
		memcpy(RGB + j*WIDTH * 3, RGB + WIDTH*HEIGHT * 3 + i*WIDTH * 3, WIDTH * 3);
	}

	//功能：将R,G,B三个字节像素值顺序调整  B、G、R----》R、G、B
	for (i = 0; (unsigned int)i < WIDTH*HEIGHT * 3; i += 3)
	{
		temp = RGB[i];
		RGB[i] = RGB[i + 2];
		RGB[i + 2] = temp;
	}
}

RGB转YU12（YUV420P）

//输入：1、申请的RGB内存(已有数据)
//	   2、申请的YUV内存
void Convert(unsigned char *RGB, unsigned char *YUV)
{
	//变量声明
	unsigned int i, x, y, j;
	unsigned char *Y = NULL;
	unsigned char *U = NULL;
	unsigned char *V = NULL;

	Y = YUV;
	U = YUV + WIDTH*HEIGHT;
	V = U + ((WIDTH*HEIGHT) >> 2);

	for (y = 0; y < HEIGHT; y++)
		for (x = 0; x < WIDTH; x++)
		{
			j = y*WIDTH + x;
			i = j * 3;
			Y[j] = (unsigned char)(DY(RGB[i], RGB[i + 1], RGB[i + 2]));

			if (x % 2 == 1 && y % 2 == 1)
			{
				j = (WIDTH >> 1) * (y >> 1) + (x >> 1);
				//上面i仍有效
				U[j] = (unsigned char)
					((DU(RGB[i], RGB[i + 1], RGB[i + 2]) +
						DU(RGB[i - 3], RGB[i - 2], RGB[i - 1]) +
						DU(RGB[i - WIDTH * 3], RGB[i + 1 - WIDTH * 3], RGB[i + 2 - WIDTH * 3]) +
						DU(RGB[i - 3 - WIDTH * 3], RGB[i - 2 - WIDTH * 3], RGB[i - 1 - WIDTH * 3])) / 4);

				V[j] = (unsigned char)
					((DV(RGB[i], RGB[i + 1], RGB[i + 2]) +
						DV(RGB[i - 3], RGB[i - 2], RGB[i - 1]) +
						DV(RGB[i - WIDTH * 3], RGB[i + 1 - WIDTH * 3], RGB[i + 2 - WIDTH * 3]) +
						DV(RGB[i - 3 - WIDTH * 3], RGB[i - 2 - WIDTH * 3], RGB[i - 1 - WIDTH * 3])) / 4);
			}

		}
}

YU12转NV12

void YU12_to_NV12(	unsigned char* Src,
					unsigned char* Dst, 
					int Width, 
					int Height) {

	unsigned char* SrcU = Src + Width * Height;
	unsigned char* SrcV = SrcU + Width * Height / 4;
	memcpy(Dst, Src, Width * Height);
	unsigned char* DstU = Dst + Width * Height;
	for (int i = 0; i < Width * Height / 4; i++) {
		(*DstU++) = (*SrcU++);
		(*DstU++) = (*SrcV++);
	}
}

YU12转NV21

void YU12_to_NV21(unsigned char *Src,
				   unsigned char *Dst, 
				   int Width, 
				   int Height){

	unsigned char* SrcU = Src + Width * Height;
	unsigned char* SrcV = SrcU + Width * Height / 4;
	memcpy(Dst, Src, Width * Height);
	unsigned char* DstV = Dst + Width * Height;
	for (int i = 0; i < Width * Height / 4; i++)
	{
		(*DstV++) = (*SrcV++);
		(*DstV++) = (*SrcU++);
	}
}

NV12转YU12

void NV12_to_YU12(	const unsigned char* image_src,
					unsigned char* image_dst,
					int image_width,
					int image_height) {
	unsigned char* p = image_dst;
	memcpy(p, image_src, image_width * image_height * 3 / 2);
	const unsigned char* pNV = image_src + image_width * image_height;
	unsigned char* pU = p + image_width * image_height;
	unsigned char* pV = p + image_width * image_height + ((image_width * image_height) >> 2);
	for (int i = 0; i<(image_width * image_height) / 2; i++) {
		if ((i % 2) == 0)
		{
			memcpy(pU, pNV + i, 1);
			pU++;
		}
		else {
			memcpy(pV, pNV + i, 1);
			pV++;
		}
	}
}

NV21转YU12

void NV21_to_YU12(const unsigned char* image_src,
				  unsigned char* image_dst,
				  int image_width,
				  int image_height) {

	unsigned char* p = image_dst;
	memcpy(p, image_src, image_width * image_height * 3 / 2);
	const unsigned char* pNV = image_src + image_width * image_height;
	unsigned char* pU = p + image_width * image_height;
	unsigned char* pV = p + image_width * image_height + ((image_width * image_height) >> 2);
	for (int i = 0; i < (image_width * image_height) / 2; i++) {
		if ((i % 2) == 0)
		{
			memcpy(pU, pNV + i, 1);
			pU++;
		}
		else {
			memcpy(pV, pNV + i, 1);
			pV++;
		}
	}
}