C++——bmp圖像+中值濾波

1、中值濾波

       中值濾波是對一個滑動窗口內的諸像素灰度值排序，用其中值代替窗口中心象素的原來灰度值，它是一種非線性的圖像平滑法，它對脈衝干擾級椒鹽噪聲的抑制效果好，在抑制隨機噪聲的同時能有效保護邊緣少受模糊。

       二維中值濾波算法是：對於一幅圖像的象素矩陣，取以目標象素爲中心的一個子矩陣窗口，這個窗口可以是3*3 ，5*5 等根據需要選取，對窗口內的象素灰度排序，取中間一個值作爲目標象素的新灰度值。

步驟：

1：通過從圖像中的某個採樣窗口取出奇數個數據進行排序

       在這裏，我們選用的排序方法是冒泡排序

2：用排序後的中值取代要處理的數據即可

       一般的，中值濾波對圖像的邊界用0做擴張，所以對邊界可能會出現扭曲。在這裏，我對邊界進行了填充，用裏圈的值來填充外圈的值。若要用0填充外圈，可將imagedatafilter初始化爲0：

memset(imagedatafilter,0,linebyte*bmpHeight);

如果這樣，那填充的那個循環就可以去掉不要了，具體代碼如下：

#include <cstring>
#include <windows.h>
#include"readbmp.h"
#include"savebmp.h"
#include<assert.h>

#define iFilterW 3
#define iFilterH 3


unsigned char GetMedianNum(int * bArray, int iFilterLen)
{
	int i, j;// 循環變量  
	unsigned char bTemp;

	// 用冒泡法對數組進行排序  
	for (j = 0; j < iFilterLen - 1; j++)
	{
		for (i = 0; i < iFilterLen - j - 1; i++)
		{
			if (bArray[i] > bArray[i + 1])
			{
				// 互換  
				bTemp = bArray[i];
				bArray[i] = bArray[i + 1];
				bArray[i + 1] = bTemp;
			}
		}
	}

	// 計算中值  
	if ((iFilterLen & 1) > 0)
	{
		// 數組有奇數個元素，返回中間一個元素  
		bTemp = bArray[(iFilterLen + 1) / 2];
	}
	else
	{
		// 數組有偶數個元素，返回中間兩個元素平均值  
		bTemp = (bArray[iFilterLen / 2] + bArray[iFilterLen / 2 + 1]) / 2;
	}

	return bTemp;
}


void image_filter_median()
{
	char readPath[] = "D:\\C++_file\\image_deal_C++\\IMAGE_JIEQU\\jiaoyan.bmp";
	readBmp(readPath);

	unsigned char *imagedatafilter;
	unsigned char *imagedata;
	imagedata = pBmpBuf;
	int  aValue[iFilterH*iFilterW];          // 指向濾波器數組的指針  

	int lineByte = (bmpWidth * biBitCount / 8 + 3) / 4 * 4;
	imagedatafilter = new unsigned char[lineByte * bmpHeight];
	int iFilterHM= (iFilterH - 1)/ 2;
	int iFilterWM = (iFilterW - 1) / 2;


	for (int i = iFilterHM; i < bmpHeight - iFilterHM; i++)
		for (int j = iFilterWM; j < bmpWidth - iFilterWM; j++)
			for (int k = 0; k < 3; k++)
			{
				
				for (int m  = 0; m< iFilterH; m++)
					for (int n = 0; n < iFilterW; n++)
						{
							aValue[m * iFilterW + n] = *(imagedata + lineByte* (i+m-1) + (j + n-1) * 3 + k);	
						}
				*(imagedatafilter + bmpWidth * 3 * i + j * 3 + k) = GetMedianNum(aValue, iFilterH * iFilterW); 
				
			}

	for (int i = 0; i < bmpHeight; i++)
		for (int j = 0; j < bmpWidth; j++)
				for (int k = 0; k < 3; k++)
				{

					
					if ((i<iFilterHM) && (j<iFilterWM))
								*(imagedatafilter + lineByte * i + j * 3 + k) = *(imagedatafilter + lineByte* (i + iFilterHM) + (j + iFilterWM) * 3 + k);
					else if ((i<iFilterHM) && (j>=iFilterWM)&&(j<(bmpWidth - iFilterWM)))
						*(imagedatafilter + lineByte * i + j * 3 + k) = *(imagedatafilter + lineByte* (i + iFilterHM) + j  * 3 + k);
					else if ((i<iFilterHM) && ( j >= (bmpWidth - iFilterWM)))
						*(imagedatafilter + lineByte * i + j * 3 + k) = *(imagedatafilter + lineByte* (i + iFilterHM) + (j - iFilterWM) * 3 + k);
					else if ((i>=iFilterHM) && i <(bmpHeight - iFilterHM) && (j< iFilterWM))
						*(imagedatafilter + lineByte * i + j * 3 + k) = *(imagedatafilter + lineByte* i + (j + iFilterWM) * 3 + k);
					else if ((i>=iFilterHM) && i < (bmpHeight - iFilterHM) && (j >= (bmpWidth - iFilterWM)))
						*(imagedatafilter + lineByte * i + j * 3 + k) = *(imagedatafilter + lineByte* i + (j - iFilterWM) * 3 + k);
					else if ((i >= (bmpHeight - iFilterHM)) && (j< iFilterWM))
						*(imagedatafilter + lineByte * i + j * 3 + k) = *(imagedatafilter + lineByte* (i - iFilterHM) + (j + iFilterWM) * 3 + k);
					else if ((i >= (bmpHeight - iFilterHM)) && (j>= iFilterWM)&&(j<(bmpWidth - iFilterWM)))
								*(imagedatafilter + lineByte * i + j * 3 + k) = *(imagedatafilter + lineByte* (i - iFilterHM) + j * 3 + k);
					else if ((i >= (bmpHeight - iFilterHM)) && ( j >= (bmpWidth - iFilterWM)))
						*(imagedatafilter + lineByte * i + j * 3 + k) = *(imagedatafilter + lineByte* (i - iFilterHM) + (j - iFilterWM) * 3 + k);
				
					
				}


	char writePath[] = "D:\\C++_file\\image_deal_C++\\IMAGE_JIEQU\\mm.bmp";
	saveBmp(writePath, imagedatafilter, bmpWidth, bmpHeight, biBitCount, pColorTable);
	printf("中值濾波操作完成，請查看bmp文件。\n\n");
	
}

原圖：

濾波後：