Opencv 减色处理

我们将图像的值由256^3压缩至4^3，即将\text{RGB}的值只取{32, 96, 160, 224},这被称作色彩量化。色彩的值按照下面的方式定义：

val = {  32  (  0 <= val <  64)
         96  ( 64 <= val < 128)
        160  (128 <= val < 192)
        224  (192 <= val < 256)

python 实现：

import cv2
import numpy as np

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

# Dicrease color
out = img.copy()

out = out // 64 * 64 + 32

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>

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

  int width = img.rows;
  int height = img.cols;

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

  for (int j = 0; j < height; j++){
    for (int i = 0; i < width; i++){
      for (int c = 0; c < 3; c++){
    out.at<cv::Vec3b>(j,i)[c] = (uchar)(floor((double)img.at<cv::Vec3b>(j,i)[c] / 64) * 64 + 32);
      }
    }
  }

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

  return 0;
}

输入：

输出：