Opencv Motion Filter

使用3\times3的Motion Filter来进行滤波吧。

Motion Filter取对角线方向的像素的平均值，像下式这样定义：
\begin{matrix}
\frac{1}{3}&0&0\\
0&\frac{1}{3}&0\\
0 &0& \frac{1}{3}
\end{matrix}

python实现：

import cv2
import numpy as np

# motion filter
def motion_filter(img, K_size=3):
    H, W, C = img.shape

    # Kernel
    K = np.diag( [1] * K_size ).astype(np.float)
    K /= K_size

    # zero padding
    pad = K_size // 2
    out = np.zeros((H + pad * 2, W + pad * 2, C), dtype=np.float)
    out[pad: pad + H, pad: pad + W] = img.copy().astype(np.float)
    tmp = out.copy()

    # filtering
    for y in range(H):
        for x in range(W):
            for c in range(C):
                out[pad + y, pad + x, c] = np.sum(K * tmp[y: y + K_size, x: x + K_size, c])

    out = out[pad: pad + H, pad: pad + W].astype(np.uint8)

    return out


# Read image
img = cv2.imread("imori.jpg")

# motion filtering
out = motion_filter(img, K_size=3)

# Save result
cv2.imwrite("out.jpg", out)
cv2.imshow("result", out)
cv2.waitKey(0)
cv2.destroyAllWindows()

C++ 实现：

#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <iostream>
#include <math.h>


// motion filter
cv::Mat motion_filter(cv::Mat img, int kernel_size){
  int height = img.rows;
  int width = img.cols;
  int channel = img.channels();

  // prepare output
  cv::Mat out = cv::Mat::zeros(height, width, CV_8UC3);

  // prepare kernel
  int pad = floor(kernel_size / 2);

  double kernel[kernel_size][kernel_size];//{{1./3, 0, 0}, {0, 1./3, 0}, {0, 0, 1./3}};

  for(int y = 0; y < kernel_size; y++){
    for(int x = 0; x < kernel_size; x++){
      if (y == x){
        kernel[y][x] = 1. / kernel_size;
      } else {
        kernel[y][x] = 0;
      }
    }
  }

  // filtering
  double v = 0;

  for (int y = 0; y < height; y++){
    for (int x = 0; x < width; x++){
      for (int c = 0; c < channel; c++){

      v = 0;

      for (int dy = -pad; dy < pad + 1; dy++){
        for (int dx = -pad; dx < pad + 1; dx++){
          if (((y + dy) >= 0) && (( x + dx) >= 0) && ((y + dy) < height) && ((x + dx) < width)){
            v += (double)img.at<cv::Vec3b>(y + dy, x + dx)[c] * kernel[dy + pad][dx + pad];
          }
        }
      }
      out.at<cv::Vec3b>(y, x)[c] = (uchar)v;
      }
    }
  }
  return out;
}

int main(int argc, const char* argv[]){
  // read image
  cv::Mat img = cv::imread("imori.jpg", cv::IMREAD_COLOR);

  // motion filter
  cv::Mat out = motion_filter(img, 3);

  //cv::imwrite("out.jpg", out);
  cv::imshow("answer", out);
  cv::waitKey(0);
  cv::destroyAllWindows();

  return 0;
}

输入：

输出：