OpenCV图像处理专栏九 | 基于直方图的快速中值滤波算法

#include "stdafx.h"
#include <stdio.h>
#include <iostream>
#include <immintrin.h>
#include <opencv2/opencv.hpp>
using namespace cv;
using namespace std;

//计算中值
int getMediaValue(const int hist[], int thresh) {
	int sum = 0;
	for (int i = 0; i < 256; i++) {
		sum += hist[i];
		if (sum >= thresh) {
			return i;
		}
	}
	return 255;
}
//快速中值滤波，灰度图
Mat fastMedianBlur(Mat src, int diameter) {
	int row = src.rows;
	int col = src.cols;
	Mat dst(row, col, CV_8UC1);
	int Hist[256] = { 0 };
	int radius = (diameter - 1) / 2;
	int windowSize = diameter * diameter;
	int threshold = windowSize / 2 + 1;
	uchar *srcData = src.data;
	uchar *dstData = dst.data;
	int right = col - radius;
	int bot = row - radius;
	for (int j = radius; j < bot; j++) {
		for (int i = radius; i < right; i++) {
			//每一行第一个待滤波元素建立直方图
			if (i == radius) {
				memset(Hist, 0, sizeof(Hist));
				for (int y = j - radius; y <= min(j + radius, row); y++) {
					for (int x = i - radius; x <= min(i + radius, col); x++) {
						uchar val = srcData[y * col + x];
						Hist[val]++;
					}
				}
			}
			else {
				int L = i - radius - 1;
				int R = i + radius;
				for (int y = j - radius; y <= min(j + radius, row); y++) {
					//更新左边一列
					Hist[srcData[y * col + L]]--;
					//更新右边一列
					Hist[srcData[y * col + R]]++;
				}
			}
			uchar medianVal = getMediaValue(Hist, threshold);
			dstData[j * col + i] = medianVal;
		}
	}
	//边界直接赋值
	for (int i = 0; i < row; i++) {
		for (int j = 0; j < radius; j++) {
			int id1 = i * col + j;
			int id2 = i * col + col - j - 1;
			dstData[id1] = srcData[id1];
			dstData[id2] = srcData[id2];
		}
	}

	for (int i = 0; i < col; i++) {
		for (int j = 0; j < radius; j++) {
			int id1 = j * col + i;
			int id2 = (row - j - 1) * col + i;
			dstData[id1] = srcData[id1];
			dstData[id2] = srcData[id2];
		}
	}
	
	return dst;
}

void MedianFilter(int height, int width, unsigned char * __restrict src, unsigned char * __restrict dst) {
	for (int i = 1; i < height - 1; i++) {
		for (int j = 1; j < width - 1; j++) {
			unsigned char a[9];
			a[0] = src[i * width + j];
			a[1] = src[i * width + j + 1];
			a[2] = src[i * width + j - 1];

			a[3] = src[(i + 1) * width + j];
			a[4] = src[(i + 1) * width + j + 1];
			a[5] = src[(i + 1) * width + j - 1];

			a[6] = src[(i - 1) * width + j];
			a[7] = src[(i - 1) * width + j + 1];
			a[8] = src[(i - 1) * width + j - 1];
			for (int ii = 0; ii < 5; ii++) {
				for (int jj = ii + 1; jj < 9; jj++) {
					if (a[ii] > a[jj]) {
						unsigned char temp = a[ii];
						a[ii] = a[jj];
						a[jj] = temp;
					}
				}
			}
			dst[i * width + j] = a[4];
		}
	}
	for (int i = 0; i < width; i++) {
		dst[i] = src[i];
		dst[(height - 1) * width + i] = src[(height - 1) * width + i];
	}
	for (int i = 0; i < height; i++) {
		dst[i * width] = src[i * width];
		dst[i * width + width - 1] = src[i * width + width - 1];
	}
}
Mat speed_MedianFilter(Mat src) {
	int row = src.rows;
	int col = src.cols;
	unsigned char * data = (unsigned char *)src.data;
	unsigned char *dst = new unsigned char[row * col];
	MedianFilter(row, col, data, dst);
	Mat res(row, col, CV_8UC1, dst);
	return res;
}


int main() {
	Mat src = cv::imread("F:\\t1.jpg", 0);
	Mat dst1 = fastMedianBlur(src, 3);
	Mat dst2 = speed_MedianFilter(src);
	cv::imshow("dst1", dst1);
	cv::imshow("dst2", dst2);
	int row = src.rows;
	int col = src.cols;
	for (int i = 0; i < row; i++) {
		for (int j = 0; j < col; j++) {
			if (dst1.at<uchar>(i, j) != dst2.at<uchar>(i, j)) {
				printf("%d %d\n", i, j);
			}
		}
	}
	system("pause");
	cv::waitKey(0);
	return 0;
}