統計rgb與yuv檔案中各分量的熵

• • 要求
  • 提示
  • 程式碼
  • 結果
  • 分析

要求

對群裡發的down.rgb和down.yuv分析三個通道的概率分佈，並計算各自的熵。

提示

兩個檔案的解析度均為256*256，yuv為4:2:0取樣空間，儲存格式為：rgb檔案按每個畫素BGR分量依次存放；YUV格式按照全部畫素的Y資料塊、U資料塊和V資料塊依次存放。

程式碼

#include<iostream>
#include<fstream>
using namespace std;
#define height 256
#define width 256
#define size 65536
 

void H_RGB(unsigned char* buffer)
{
	FILE* fp;
	float level_r[256] = { 0 };
	float level_g[256] = { 0 };
	float level_b[256] = { 0 };
	float Hr = 0, Hg = 0, Hb = 0;
	fopen_s(&fp, "C:\\Users\\tonym\\Desktop\\down.rgb", "rb");
	if (fp == 0)
		return;
	fread(buffer, size * 3, 1, fp);
	for
 
 (int i = 0; i < size * 3; i)
	{
		level_b[buffer[i++]] ++;
		level_g[buffer[i++]] ++;
		level_r[buffer[i++]] ++;
	}
	for (int i = 0; i < 256; i++)
	{
		if (level_b[i] / 65536 != 0)
			Hb = Hb - (level_b[i] / 65536) * (log(level_b[i] / 65536) / (log(2)) );
		if (level_g[i] / 65536 != 0)
			Hg = Hg - (level_g[
 
i] / 65536) * (log(level_g[i] / 65536) / (log(2)) );
		if (level_r[i] / 65536 != 0)
			Hr = Hr - (level_r[i] / 65536) * (log(level_r[i] / 65536) / (log(2)) );
	}
	printf("Hr=%f\nHg=%f\nHb=%f\n", Hr, Hg, Hb);
}
float H_YUV(unsigned char* buffer,int len)
{
	float level[256] = { 0 };
	float H=0;
	for (int i = 0; i < len; i)
	{
		level[buffer[i++]] ++;
	}
	for (int i = 0; i < 256; i++)
	{
		if (level[i] / len != 0)
			H = H - (level[i] / len) * (log(level[i] / len) / (log(2)));
	}
	return H;
}
int main()
{

	int level_RGB[256] = { 0 };
	float sum_RGB[256];

	unsigned char* RGB_buffer;
	unsigned char* YUV_buffer1, * YUV_buffer2, * YUV_buffer3;

	RGB_buffer = new unsigned char[size * 3];
	YUV_buffer1 = new unsigned char[size];
	YUV_buffer2 = new unsigned char[size/4];
	YUV_buffer3 = new unsigned char[size/4];
	FILE* fp_yuv;
	fopen_s(&fp_yuv, "C:\\Users\\tonym\\Desktop\\down.yuv", "rb");
	if (fp_yuv == 0)
		return 0;
	fread(YUV_buffer1, 65536, 1, fp_yuv);
	fread(YUV_buffer2, 16384, 1, fp_yuv);
	fread(YUV_buffer3, 16384, 1, fp_yuv);
	H_RGB(RGB_buffer);
	printf("Hy=%f\n", H_YUV(YUV_buffer1, 65536));
	printf("Hu=%f\n", H_YUV(YUV_buffer2, 16384));
	printf("Hv=%f\n", H_YUV(YUV_buffer3, 16384));

	return 0;
}

結果

分析

yuv檔案中各分量的熵小於rgb中各分量的熵，說明rgb檔案雖然體積大於4:2:0取樣格式的yuv檔案但所含資訊量的密度更高。