C++PythonC# 三语言OpenCV从零开发(7):图像的阈值

文章目录

相关链接
前言
阈值
- 阈值使用
- - 代码
  - - Python
    - C++
    - Csharp
    - - csharp代码问题
总结

前言

我感觉我之前的比较实在是太过于偏代码了，缺少了图形学的知识的记录。之后的笔记我会把图形学的知识也记录上去。

阈值

阈值简单来说就是增强图片的对比。用过Ps的人就知道阈值是什么意思，在电脑绘画中用的还是比较多的

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阈值使用

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代码

Python

# %%
# 导入包
import cv2
import matplotlib.pyplot as plt
import numpy as npimage = {"image":'',"gray":'',}image["image"] = cv2.imread("D:/workSpace/OpenCV/HellOpenCV/Resources/image/cat.png")# 获取颜色通道，因为cv2是BGR的顺序，所以这里是B 灰度
image["gray"]= cv2.split(image['image'])[0]thresh = {'1' : '','2': '','3': '','4': '','5': ''
}# 调用不同的阈值处理算子
ret , thresh['1'] = cv2.threshold(image['gray'],127,255,cv2.THRESH_BINARY)
ret , thresh['2'] = cv2.threshold(image['gray'],127,255,cv2.THRESH_BINARY_INV)
ret , thresh['3'] = cv2.threshold(image['gray'],127,255,cv2.THRESH_TRUNC)
ret , thresh['4'] = cv2.threshold(image['gray'],127,255,cv2.THRESH_TOZERO)
ret , thresh['5'] = cv2.threshold(image['gray'],127,255,cv2.THRESH_TOZERO_INV)# 将数据总和成数组
titles = ['iamge','binary','binary inv','trunc','tozero','tozero inv']
images = [image['gray'],thresh['1'],thresh['2'],thresh['3'],thresh['4'],thresh['5']]# 循环赋值到plt中
for i in range(6):plt.subplot(2,3,i+1),plt.imshow(images[i],'gray')plt.title(titles[i])plt.xticks([]),plt.yticks([])plt.show()

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C++

这里为了一次性展示多个窗口，我就CSDN上面找了个方法

OpenCV一个窗口同时显示多张图片 (C++)


#include <opencv2/opencv.hpp>  
#include <opencv2/core/core.hpp>  
#include <opencv2/highgui/highgui.hpp>  
#include <opencv2/imgproc.hpp>  
#include<iostream>  
#include <vector>
using namespace std;
using namespace cv;vector<Mat> imageVector;void multipleImage(vector<Mat> imgVector, Mat& dst, int imgCols)
{const int MAX_PIXEL = 300;int imgNum = imgVector.size();//选择图片最大的一边 将最大的边按比例变为300像素Size imgOriSize = imgVector[0].size();int imgMaxPixel = max(imgOriSize.height, imgOriSize.width);//获取最大像素变为MAX_PIXEL的比例因子double prop = imgMaxPixel < MAX_PIXEL ? (double)imgMaxPixel / MAX_PIXEL : MAX_PIXEL / (double)imgMaxPixel;Size imgStdSize(imgOriSize.width * prop, imgOriSize.height * prop); //窗口显示的标准图像的SizeMat imgStd; //标准图片Point2i location(0, 0); //坐标点(从0,0开始)//构建窗口大小 通道与imageVector[0]的通道一样Mat imgWindow(imgStdSize.height * ((imgNum - 1) / imgCols + 1), imgStdSize.width * imgCols, imgVector[0].type());for (int i = 0; i < imgNum; i++){location.x = (i % imgCols) * imgStdSize.width;location.y = (i / imgCols) * imgStdSize.height;resize(imgVector[i], imgStd, imgStdSize, prop, prop, INTER_LINEAR); //设置为标准大小imgStd.copyTo(imgWindow(Rect(location, imgStdSize)));}dst = imgWindow;
}int main()
{auto image = imread("D:/workSpace/OpenCV/HellOpenCV/Resources/image/cat.png");Mat showImage;Mat bgr[3];split(image, bgr);Mat gray = bgr[0];Mat thresh[5];threshold(gray, thresh[0], 127, 255, THRESH_BINARY);threshold(gray, thresh[1], 127, 255, THRESH_BINARY_INV);threshold(gray, thresh[2], 127, 255, THRESH_TRUNC);threshold(gray, thresh[3], 127, 255, THRESH_TOZERO);threshold(gray, thresh[4], 127, 255, THRESH_TOZERO_INV);vector<Mat> images{gray,thresh[0],thresh[1], thresh[2], thresh[3], thresh[4], };multipleImage(images, showImage, 3);imshow("C++", showImage);waitKey(0);destroyAllWindows();return 0;
}

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Csharp

还是那句话，C++跑通了，Csharp抄抄就可以了。
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using OpenCvSharp;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;namespace HelloOpenCV.Utils
{public static class MyOpenCV_Extensions{/// <summary>/// 3通道遍历/// </summary>/// <param name="mat"></param>/// <returns></returns>public static int[,,] MatToArray(Mat mat){var res = new int[mat.Rows, mat.Cols, mat.Channels()];for (var i = 0; i < mat.Rows; i++){for (var j = 0; j < mat.Cols; j++){var temp = mat.At<Vec3b>(i, j);res[i, j, 0] = temp[0];res[i, j, 1] = temp[1];res[i, j, 2] = temp[2];}}return res;}public static Mat MultipleImage(List<Mat> lists, int imgCols){const int MAX_PIXEL = 300;int imgNum = lists.Count;//选择图片最大的一边 将最大的边按比例变为300像素Size imgOriSize = lists[0].Size();int imgMaxPixel = Math.Max(imgOriSize.Height, imgOriSize.Width);//获取最大像素变为MAX_PIXEL的比例因子double prop = imgMaxPixel < MAX_PIXEL ? (double)imgMaxPixel / MAX_PIXEL : MAX_PIXEL / (double)imgMaxPixel;Size imgStdSize= new Size(imgOriSize.Width* prop, imgOriSize.Height* prop); //窗口显示的标准图像的SizeMat imgStd = new Mat(); //标准图片Point location = new Point(0, 0); //坐标点(从0,0开始)//构建窗口大小 通道与imageVector[0]的通道一样Mat imgWindow = new Mat(imgStdSize.Height* ((imgNum -1) / imgCols + 1), imgStdSize.Width* imgCols, lists[0].Type());for (int i = 0; i < imgNum; i++){location.X = (i % imgCols) * imgStdSize.Width;location.Y = (i / imgCols) * imgStdSize.Height;Cv2.Resize(lists[i], imgStd, imgStdSize, prop, prop, InterpolationFlags.Linear); //设置为标准大小imgStd.CopyTo(new Mat(imgWindow, new Rect(location, imgStdSize)) ); }return imgWindow;}}
}

运行代码

 static void Main(string[] args){Mat image = Cv2.ImRead("D:/workSpace/OpenCV/HellOpenCV/Resources/image/cat.png");Mat[] bgr = new Mat[3];Cv2.Split(image, out bgr);Mat gray = bgr[0];Mat[] threshs = new Mat[5];for(var i = 0; i < threshs.Length; i++){threshs[i] = new Mat();}Cv2.Threshold(gray, threshs[0], 127, 255, ThresholdTypes.Binary);Cv2.Threshold(gray, threshs[1], 127, 255, ThresholdTypes.BinaryInv);Cv2.Threshold(gray, threshs[2], 127, 255, ThresholdTypes.Trunc);Cv2.Threshold(gray, threshs[3], 127, 255, ThresholdTypes.Tozero);Cv2.Threshold(gray, threshs[4], 127, 255, ThresholdTypes.TozeroInv);var res = MyOpenCV_Extensions.MultipleImage(new List<Mat>() {gray, threshs[0], threshs[1], threshs[2], threshs[3], threshs[4] }, 3);Cv2.ImShow("Csharp", res);Cv2.WaitKey(0);Cv2.DestroyAllWindows();}