1 分离YUV420中YUV分量
本程序中的函数主要是将YUV420P视频数据流的第一帧图像中的Y、U、V三个分量分离开并保存成三个文件。函数的代码如下所示:
/**
* @file 1 yuv_split.cpp
* @author luohen
* @brief split of yuv
* @date 2018-12-07
*
*/
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <iostream>
using namespace std;
/**
* @brief
*
* @param url location of input yuv420p file
* @param w width of input yuv420p file
* @param h height of input yuv420p file
* @return int
*/
int yuv420_split(const char *url, int w, int h)
{
//reading yuv image
FILE *input_fp;
if ((input_fp = fopen(url, "rb")) == NULL)
{
printf("%s open error!\n", url);
return -1;
}
else
{
printf("%s open.\n", url);
}
//writing yuv image
FILE *outputY_fp = fopen("video_result/output_420_y.y", "wb+");
FILE *outputU_fp = fopen("video_result/output_420_u.y", "wb+");
FILE *outputV_fp = fopen("video_result/output_420_v.y", "wb+");
unsigned char *pic = new unsigned char[w * h * 3 / 2];
//读数据,每次读取的字节数为sizeof(unsigned char)=1,共读取w*h*3/2次
//reading data
fread(pic, sizeof(unsigned char), w * h * 3 / 2, input_fp);
//writing data
//Y
fwrite(pic, sizeof(unsigned char), w * h, outputY_fp);
//U
fwrite(pic + w * h, sizeof(unsigned char), w * h / 4, outputU_fp);
//V
fwrite(pic + w * h * 5 / 4, sizeof(unsigned char), w * h / 4, outputV_fp);
//memory release and files closing
delete[] pic;
fclose(input_fp);
fclose(outputY_fp);
fclose(outputU_fp);
fclose(outputV_fp);
return 0;
}
/**
* @brief main
*
* @return int
*/
int main()
{
//Setting YUV information
int state = yuv420_split("video/akiyo.yuv", 352, 288);
return 0;
}
调用函数为:
int yuv420_split(const char *url, int w, int h);
从代码可以看出,程序先是读入一段视频数据流。通过fread函数读取w*h*3/2个unsigned char长度的数据实现第一帧图像的读取,unsigned char占一个字节(通过sizeof(unsigned char)可以查看到),也就是说fread函数读取w*h*3/2字节的数据就可以实现一帧图像的读取。
其中这段代码的fread函数是指每次读取1个字节的数据,一共读取w*h(y的长度)+(w/2*h/2)(u的长度)+ (w/2*h/2)(v的长度)=w*h*3/2次。
fread(pic, sizeof(unsigned char), w * h * 3 / 2, input_fp);
写成下列形式也是一样的。
fread(pic, w * h * 3 / 2*sizeof(unsigned char), 1, input_fp);
fwrite函数也是一样的用法。先存Y,再存UV。对于Y,U,Y分离后存储的格式可以是yuv格式也可以是单独的y格式。分离后的Y分量(352,288),U分量(176,144),V分量(176,144)。结果如下图所示:
2 YUV420灰度化
本程序中的函数主要是将YUV420P视频数据流的第一帧图像变为灰度图像。函数的代码如下所示:
/**
* @file 2 yuv_gray.cpp
* @author luohen
* @brief gray scale of yuv
* @date 2018-12-07
*
*/
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <iostream>
using namespace std;
/**
* @brief
*
* @param url location of input yuv420p file
* @param w width of input yuv420p file
* @param h height of input yuv420p file
* @return int
*/
int yuv420_gray(const char *url, int w, int h)
{
//reading yuv image
FILE *input_fp;
if ((input_fp = fopen(url, "rb")) == NULL)
{
printf("%s open error!\n", url);
return -1;
}
else
{
printf("%s open.\n", url);
}
//writing yuv image
FILE *outputGray_fp = fopen("video_result/output_gray.yuv", "wb+");
unsigned char *pic = new unsigned char[w * h * 3 / 2];
fread(pic, sizeof(unsigned char), w * h * 3 / 2, input_fp);
//Gray
//把pic+w*h开始所有的数据置为128,色度分量取值范围是-128至127,量化后范围为0至255
//uv=128,实现灰度化
memset(pic + w * h, 128, w * h / 2);
fwrite(pic, sizeof(unsigned char), w * h * 3 / 2, outputGray_fp);
delete[] pic;
fclose(input_fp);
fclose(outputGray_fp);
return 0;
}
/**
* @brief main函数
*
* @return int
*/
int main()
{
int state = yuv420_gray("video/akiyo.yuv", 352, 288);
return 0;
}
调用函数为:
int yuv420_gray(const char *url, int w, int h);
这段函数主要是将U、V分量置为128,从而得到灰度图像。将U、V置为128而不是0,主要原因是U、V本来的取值范围大概是-127到128(可能更大),因为YUV的数据流是无符号的,所以将其量化为0到255。UV的最初取值范围可以通过RGB与YUV的转换公式理解。具体见文章:
最终得到的YUV灰度图像,UV分量都存在只是为128而已。事实上只提取出Y分量效果也是一样的。结果如下图所示:
3 YUV420亮度减半
本程序中的函数主要是将YUV420P视频数据流的第一帧图像亮度减半。函数的代码如下所示:
/**
* @file 3 yuv_halfy.cpp
* @author luohen
* @brief Half of Y value
* @date 2018-12-07
*
*/
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <iostream>
using namespace std;
/**
* @brief
*
* @param url location of input yuv420p file
* @param w width of input yuv420p file
* @param h height of input yuv420p file
* @return int
*/
int yuv420_half(const char *url, int w, int h)
{
//reading yuv image
FILE *input_fp;
if ((input_fp = fopen(url, "rb")) == NULL)
{
printf("%s open error!\n", url);
return -1;
}
else
{
printf("%s open.\n", url);
}
//writing yuv image
FILE *output_fp = fopen("video_result/output_half.yuv", "wb+");
unsigned char *pic = new unsigned char[w * h * 3 / 2];
fread(pic, sizeof(unsigned char), w * h * 3 / 2, input_fp);
//half of Y
for (int j = 0; j < w * h; j++)
{
unsigned char temp = pic[j] / 2;
//printf("%d,\n",temp);
pic[j] = temp;
}
fwrite(pic, 1, w * h * 3 / 2, output_fp);
delete[] pic;
fclose(input_fp);
fclose(output_fp);
return 0;
}
/**
* @brief main函数
*
* @return int
*/
int main()
{
int state = yuv420_half("video/akiyo.yuv", 352, 288);
return 0;
}
调用函数为:
int yuv420_half(const char *url, int w, int h);
这段函数主要是将Y分量减半,从而得到灰度图像。而其他UV分量不需要调整。实际上YUV图像处理套路就是将YUV三个分量分别看成三张灰度图像,分别进行图像处理。除了YUV分量大小不一,其他与RGB像素处理一样。结果如下图所示:
4 YUV420添加边框
本程序中的函数主要是为YUV420P视频数据流的第一帧图像添加边框。函数的代码如下所示:
/**
* @file 4 yuv_border.cpp
* @author luohen
* @brief add a border to yuv
* @date 2018-12-07
*
*/
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <iostream>
using namespace std;
/**
* @brief
*
* @param url location of input yuv420p file
* @param w width of input yuv420p file
* @param h height of input yuv420p file
* @return int
*/
int yuv420_border(const char *url, int w, int h)
{
//reading yuv image
FILE *input_fp;
if ((input_fp = fopen(url, "rb")) == NULL)
{
printf("%s open error!\n", url);
return -1;
}
else
{
printf("%s open.\n", url);
}
//writing yuv image
FILE *output_fp = fopen("video_result/output_border.yuv", "wb+");
//border width
int border = 30;
unsigned char *pic = new unsigned char[w * h * 3 / 2];
//reading y
fread(pic, 1, w * h * 3 / 2, input_fp);
//y
for (int j = 0; j < h; j++)
{
for (int k = 0; k < w; k++)
{
if (k < border || k >(w - border) || j < border || j >(h - border))
{
//0最暗,255最亮
pic[j * w + k] = 0;
//pic[j*w+k]=255;
}
}
}
fwrite(pic, 1, w * h * 3 / 2, output_fp);
delete[] pic;
fclose(input_fp);
fclose(output_fp);
return 0;
}
/**
* @brief main函数
*
* @return int
*/
int main()
{
int state = yuv420_border("video/akiyo.yuv", 352, 288);
return 0;
}
调用函数为:
int yuv420_border(const char *url, int w, int h);
这段函数主要是调整图像边缘的Y分量数值,从而为图像添加边框。其中Y的初始值就是0-255,和灰度图一样,y为0时图像最暗,为255图像最暗。但是这段程序并没有实现严格意义上的添加图像边框,应该使得uv分量相同位置处的值为128(因为copy雷神代码。就懒得自己写了)。
结果如下图所示:
但是想了下,还是不能全copy雷神的代码。uv分量相同位置处的值为128,代码如下:
/**
* @file 4 yuv_border.cpp
* @author luohen
* @brief add a border to yuv
* @date 2018-12-07
*
*/
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <iostream>
using namespace std;
/**
* @brief
*
* @param url location of input yuv420p file
* @param w width of input yuv420p file
* @param h height of input yuv420p file
* @return int
*/
int yuv420_border(const char *url, int w, int h)
{
//reading yuv image
FILE *input_fp;
if ((input_fp = fopen(url, "rb")) == NULL)
{
printf("%s open error!\n", url);
return -1;
}
else
{
printf("%s open.\n", url);
}
//writing yuv image
FILE *output_fp = fopen("video_result/output_border.yuv", "wb+");
//border width
int border = 30;
unsigned char *pic = new unsigned char[w * h * 3 / 2];
//reading y
fread(pic, 1, w * h * 3 / 2, input_fp);
//y
for (int j = 0; j < h; j++)
{
for (int k = 0; k < w; k++)
{
if (k < border || k >(w - border) || j < border || j >(h - border))
{
//0最暗,255最亮
pic[j * w + k] = 0;
//pic[j*w+k]=255;
}
}
}
//u
for (int j = 0; j < h / 2; j++)
{
for (int k = 0; k < w / 2; k++)
{
if (k < border / 2 || k >(w / 2 - border / 2) || j < border / 2 || j >(h / 2 - border / 2))
{
pic[w*h + j * w / 2 + k] = 128;
//pic[j*w+k]=255;
}
}
}
//v
for (int j = 0; j < h / 2; j++)
{
for (int k = 0; k < w / 2; k++)
{
if (k < border / 2 || k >(w / 2 - border / 2) || j < border / 2 || j >(h / 2 - border / 2))
{
pic[w*h + w / 2 * h / 2 + j * w / 2 + k] = 128;
//pic[j*w+k]=255;
}
}
}
fwrite(pic, 1, w * h * 3 / 2, output_fp);
delete[] pic;
fclose(input_fp);
fclose(output_fp);
return 0;
}
/**
* @brief main函数
*
* @return int
*/
int main()
{
int state = yuv420_border("video/akiyo.yuv", 352, 288);
return 0;
}
其中对uv处理时border要除以2,因u、v只有y的四分之一大小。
对u,v赋值代码如下,因为yuv420是以数据流依次存储。所以u处理时数据u从pic[w*h]开始,而处理v从pic[w*h+w/2*h/2]开始。
pic[w*h + j * w / 2 + k] = 128;
pic[w*h + w / 2 * h / 2 + j * w / 2 + k] = 128;
结果如图所示:
标签:fp,入门,int,pic,YUV,char,图像处理,input,border From: https://blog.51cto.com/luohenyueji/5950125