DPCM编码进行图像压缩

程序员文章站 2022-07-14 19:06:12

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DPCM的编解码原理如下： DPCM编码进行图像压缩
编码思路：

主程序代码：main.cpp

#include "pch.h"
#include <iostream>
#include<math.h>
#include<malloc.h>
using namespace std;
const int w = 500;
const int h = 500;
const int depth = 5;
const int N = w * h;

int main(int argc, char *argv[])
{
	FILE* yuvFile = NULL;
	FILE* reFile = NULL;
	FILE* peFile = NULL;

	errno_t err;
	err = fopen_s(&yuvFile, "seed.yuv", "rb");
	if (err != 0)
	{
		printf("cannot open yuv file\n");
	}
	errno_t err1;
	err1 = fopen_s(&reFile, "re.yuv", "wb");
	if (err1 != 0)
	{
		printf("cannot open refile\n");
	}
	errno_t err2;
	err2 = fopen_s(&peFile, "pe.yuv", "wb");
	if (err2 != 0)
	{
		printf("cannot open prediction error file\n");
	}
	
	unsigned char* yBuf = (unsigned char*)malloc(sizeof(unsigned char) * N);
	unsigned char* uBuf = (unsigned char*)malloc(sizeof(unsigned char) * N );
	unsigned char* vBuf = (unsigned char*)malloc(sizeof(unsigned char) * N );
	unsigned char* reBuf = (unsigned char*)malloc(sizeof(unsigned char) * N);//重建图像
	unsigned char* peBuf = (unsigned char*)malloc(sizeof(unsigned char) * N);//预测误差  prediction error

	fread(yBuf, sizeof(unsigned char), N, yuvFile);
	fread(uBuf, sizeof(unsigned char), N , yuvFile);
	fread(vBuf, sizeof(unsigned char), N , yuvFile);

	dpcm(h, w, yBuf, depth, reBuf, peBuf);

	fwrite(reBuf, sizeof(unsigned char), N, reFile);
	fwrite(uBuf, sizeof(unsigned char), N , reFile);
	fwrite(vBuf, sizeof(unsigned char), N , reFile);
	fwrite(peBuf, sizeof(unsigned char), N, peFile);
	fwrite(uBuf, sizeof(unsigned char), N, peFile);
	fwrite(vBuf, sizeof(unsigned char), N, peFile);

	fclose(yuvFile);
	fclose(reFile);
	free(yBuf);
	free(vBuf);
	free(uBuf);
	free(reBuf);
	free(peBuf);
}

DPCM编码代码:DPCM.cpp

void dpcm(int h,int w,unsigned char *Y_Buf,int depth,unsigned char *reBuf,unsigned char *preErr)
{
	int prediction,err,inerr;//预测值和差值
	int extend;
	for (int i = 0; i < h; i++){
		for (int j = 0; j < w; j++){
			if (j == 0) {
				prediction = 128;
				err = Y_Buf[i*w] - prediction;
				extend = (err + 128) / pow(2, 8 - depth);
				preErr[i*w + j] = extend;
				if (preErr[i*w + j] < 0) {
					preErr[i*w + j] = 0;
				}
				else if (preErr[i*w + j] > pow(2, depth) - 1) {
					preErr[i*w + j] = pow(2, depth) - 1;
				}
				inerr = preErr[i*w] * pow(2, 8 - depth);
				reBuf[i*w + j] = inerr;
				if (reBuf[i*w + j] < 0) {
					reBuf[i*w + j] = 0;
				}
				else if (reBuf[i*w + j] > 255) {
					reBuf[i*w + j] = 255;
				}
			}
			else {
				prediction = reBuf[i*w + j - 1];
				err = Y_Buf[i*w + j] - prediction;
				extend = (err + 255) / pow(2, 9 - depth);//拓展为8bit量化
				preErr[i*w + j] = extend;
				if (preErr[i*w + j] < 0) {
					preErr[i*w+j] = 0;
				}
				else if (preErr[i*w + j] > pow(2, depth) - 1) {
					preErr[i*w+j] = pow(2, depth) - 1;
				}
				inerr = preErr[i*w + j] * pow(2, 9 - depth) - 255 + prediction;
				reBuf[i*w + j] = inerr;
				if (reBuf[i*w + j] < 0) {
					reBuf[i*w+j] = 0;
				}
				else if (reBuf[i*w + j] > 255) {
					reBuf[i*w+j] = 255;
				}
			}
		}
	}
}

计算PSNR

void psnr(int w,int h,unsigned char *Y_Buf,unsigned char *reBuf,int depth) //计算图像的压缩质量
{
	FILE* psnrtxt;
	fopen_s(&psnrtxt, "psnr.txt", "ab");
	double psnr = 0;
	double mse = 0;
	for (int i = 0; i < w*h; i++) {
		mse += pow((Y_Buf[i] - reBuf[i]), 2);
	}
	mse = mse / (w * h);
	psnr = 10 * log10(255 * 255 / mse);
	fprintf(psnrtxt,"Bit=%d,psnr=%lf\n", depth,psnr);//写入文件
}