YUV420P 灰阶测试图小例

最近在学习雷神的YUV生成420P的灰阶测试图

自己仿写了雷神的接口simplest_yuv420_graybar，在代码中加入了一些注释, 记录下来

【注】:

在Y分量取值方面, 雷神的程序将0~255分成了9份, 即最后一个色柱可以取到255

而我自己的程序将0~255分成了10份, 最后一个色柱取不到最大亮度255

代码的大概意思是malloc三块内存data_y，data_u，data_v，并分别将YUV值按照要求写入

开辟一块writeBuff用于将data_y，data_u，data_v装在一起, 最后将writeBuff的内容写入文件即可

#include"common_head.h"
#define MAX_LEN (1*1024*1024)
int simplest_yuv420_graybar(int width, int height, int ymin, int ymax, int barnum, char* url_out)
{
	int barwidth = 0;//garybar width

	float lum_inc = 0.0;//luma_increase
	unsigned char lum_temp = '\0';//each column's luma value

	int fd_ori = -1;//file descriptor
	unsigned char* data_y = NULL;
	unsigned char* data_u = NULL;
	unsigned char* data_v = NULL;

	int t = 0, i = 0, j = 0;//for circle
	int s32Ret = 0;
	unsigned char writeBuff[MAX_LEN] = {'\0'};
	
	/*if width = 640;barnum = 10;then barwidth = 64*/
	barwidth = width / barnum;

	/*luma_increase number of each column*/
	/*if ymax = 255;ymin = 0;barnum = 10;then lum_inc = 25.5*/
	lum_inc = ((float)(ymax - ymin)) / ((float)(barnum));

	/*malloc memories*/
	data_y = (unsigned char*)malloc(width * height);
	if(NULL == data_y)
	{
		printf("malloc memory for Y failed!\n");
		return -1;
	}

	data_u = (unsigned char*)malloc(width * height / 4);
	if(NULL == data_u)
	{
		printf("malloc memory for U failed!\n");
		free(data_y);
		return -1;
	}

	data_v = (unsigned char*)malloc(width * height / 4);
	if(NULL == data_v)
	{
		printf("malloc memory for V failed!\n");
		free(data_u);
		free(data_y);
		return -1;
	}
	printf("malloc success!\n");

	/*open the source file*/
	fd_ori = open(url_out, O_WRONLY|O_CREAT|O_TRUNC|O_APPEND, 777);
	if(fd_ori < 0)
	{
		printf("failed to open file!\n");
		free(data_v);
		free(data_u);
		free(data_y);
		return -1;
	}

	/*width:640; height:360; barnum:10; barwidth:64; lum_inc:25.5*/
	printf("Y U V value from pic's left to right:\n");
	for(t = 0; t < barnum; t++)
	{
		lum_temp = (unsigned char)(t * lum_inc);
		printf("bar[%d]'s luma = %d\n",t, lum_temp);
	}

	/*process the Y data*/
	memset(data_y, 0, width * height);
	for(i = 0; i < height; i++)
	{
		for(j = 0; j < barnum; j++)
		{
			memset(data_y + j * barwidth + i * width, (unsigned char)(j * lum_inc), barwidth);
		}
	}

	/*process the U data*/
	memset(data_u, 0, (width * height / 4));
	memset(data_u, 128, (width * height / 4));

	/*process the V data*/
	memset(data_v, 0, (width * height / 4));
	memset(data_v, 128, (width * height / 4));

	/*write the data back*/
	memset(writeBuff, 0, sizeof(writeBuff));
	memcpy(writeBuff, data_y, width * height);
	memcpy(writeBuff + width * height, data_u, width * height / 4);
	memcpy(writeBuff + width * height + width * height / 4, data_v, width * height / 4);
	s32Ret = write(fd_ori, writeBuff, width * height * 3 / 2);
	if(s32Ret < 0)
	{
		printf("write the whole file failed!\n");
		close(fd_ori);
		free(data_v);
		free(data_u);
		free(data_y);
		return -1;
	}
	printf("write success!\n");

	/*close and free memory...*/
	close(fd_ori);
	free(data_v);
	free(data_u);
	free(data_y);
	printf("process success!\n");
	return 0;
}

效果如下:

源博客地址:

https://blog.csdn.net/leixiaohua1020/article/details/50534150