SKPath是SkiaSharp中用于创建复杂图形路径的重要类。它可以用来绘制直线、曲线、圆弧等各种图形，并且支持填充和描边操作。本文将详细介绍SKPath的使用方法和常见应用场景。

基础知识

在WinForms中使用SkiaSharp，首先需要安装以下NuGet包：

• SkiaSharp
• SkiaSharp.Views
• SkiaSharp.Views.WindowsForms

完整示例代码

C#
using SkiaSharp.Views.Desktop;
using SkiaSharp;

namespace AppSKPath
{
    public partial class Form1 : Form
    {
        private SKControl skControl;

        public Form1()
        {
            InitializeComponent();

            // 创建SKControl控件
            skControl = new SKControl();
            skControl.Dock = DockStyle.Fill;
            skControl.PaintSurface += OnPaintSurface;
            this.Controls.Add(skControl);
        }

        private void OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
        {
            // 获取绘图表面
            SKSurface surface = e.Surface;
            SKCanvas canvas = surface.Canvas;

            // 清空画布
            canvas.Clear(SKColors.White);

            // 1. 基础路径绘制
            using (var path = new SKPath())
            using (var paint = new SKPaint())
            {
                // 设置画笔属性
                paint.Style = SKPaintStyle.Stroke;
                paint.Color = SKColors.Blue;
                paint.StrokeWidth = 2;
                paint.IsAntialias= true;
               

                // 移动到起始点
                path.MoveTo(50, 50);
                // 绘制直线
                path.LineTo(150, 50);
                path.LineTo(150, 150);
                path.LineTo(50, 150);
                // 闭合路径
                path.Close();

                // 绘制路径
                canvas.DrawPath(path, paint);
            }

            // 2. 曲线路径示例
            using (var path = new SKPath())
            using (var paint = new SKPaint())
            {
                paint.Style = SKPaintStyle.Stroke;
                paint.Color = SKColors.Red;
                paint.StrokeWidth = 2;
                paint.IsAntialias = true;
                // 二次贝塞尔曲线
                path.MoveTo(200, 50);
                path.QuadTo(250, 0, 300, 50);

                // 三次贝塞尔曲线
                path.MoveTo(200, 100);
                path.CubicTo(225, 75, 275, 125, 300, 100);

                canvas.DrawPath(path, paint);
            }

            // 3. 圆弧路径示例
            using (var path = new SKPath())
            using (var paint = new SKPaint())
            {
                paint.Style = SKPaintStyle.Stroke;
                paint.Color = SKColors.Green;
                paint.StrokeWidth = 2;
                paint.IsAntialias = true;
                // 绘制圆弧
                var rect = new SKRect(350, 50, 450, 150);
                path.AddArc(rect, 0, 180); // 从0度开始，绘制180度的圆弧

                canvas.DrawPath(path, paint);
            }

            // 4. 复合路径示例（填充）
            using (var path = new SKPath())
            using (var paint = new SKPaint())
            {
                paint.Style = SKPaintStyle.Fill;
                paint.Color = SKColors.Orange;
                paint.IsAntialias = true;
                // 创建一个五角星
                float centerX = 500;
                float centerY = 100;
                float radius = 50;

                for (int i = 0; i < 5; i++)
                {
                    double angle = i * 4 * Math.PI / 5 - Math.PI / 2;
                    float x = centerX + radius * (float)Math.Cos(angle);
                    float y = centerY + radius * (float)Math.Sin(angle);

                    if (i == 0)
                        path.MoveTo(x, y);
                    else
                        path.LineTo(x, y);
                }
                path.Close();

                canvas.DrawPath(path, paint);
            }
        }
    }
}

SkiaSharp 是一个强大的 2D 图形引擎，可以用来绘制各种图形。本文将详细介绍如何使用 SkiaSharp 在 WinForm 应用中绘制多边形。

环境准备

首先需要通过 NuGet 包管理器安装以下包：

• SkiaSharp
• SkiaSharp.Views
• SkiaSharp.Views.WindowsForms

完整示例代码

C#
using SkiaSharp;
using SkiaSharp.Views.Desktop;
using System;
using System.Windows.Forms;

namespace SkiaSharpDemo
{
    public partial class Form1 : Form
    {
        private SKControl skControl;

        public Form1()
        {
            InitializeComponent();
            InitializeSkiaSharp();
        }

        private void InitializeSkiaSharp()
        {
            // 创建 SKControl 控件
            skControl = new SKControl();
            skControl.Dock = DockStyle.Fill;
            skControl.PaintSurface += OnPaintSurface;
            this.Controls.Add(skControl);
        }

        private void OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
        {
            // 获取绘图表面
            SKSurface surface = e.Surface;
            SKCanvas canvas = surface.Canvas;

            // 清空画布
            canvas.Clear(SKColors.White);

            // 创建画笔
            using (SKPaint paint = new SKPaint())
            {
                paint.Style = SKPaintStyle.Stroke; // 设置为描边模式
                paint.Color = SKColors.Blue;       // 设置颜色为蓝色
                paint.StrokeWidth = 2;            // 设置线宽为2像素
                paint.IsAntialias = true;         // 启用抗锯齿

                // 1. 绘制三角形
                DrawTriangle(canvas, paint);

                // 2. 绘制正方形
                paint.Color = SKColors.Red;
                DrawSquare(canvas, paint);

                // 3. 绘制五边形
                paint.Color = SKColors.Green;
                DrawPentagon(canvas, paint);

                // 4. 绘制六边形
                paint.Color = SKColors.Purple;
                DrawHexagon(canvas, paint);

                // 5. 绘制自定义多边形
                paint.Color = SKColors.Orange;
                DrawCustomPolygon(canvas, paint);
            }
        }

        // 绘制三角形
        private void DrawTriangle(SKCanvas canvas, SKPaint paint)
        {
            // 创建路径
            using (SKPath path = new SKPath())
            {
                // 定义三角形的三个顶点
                path.MoveTo(50, 50);           // 起始点
                path.LineTo(150, 50);          // 第二个点
                path.LineTo(100, 150);         // 第三个点
                path.Close();                  // 闭合路径

                // 绘制路径
                canvas.DrawPath(path, paint);
            }
        }

        // 绘制正方形
        private void DrawSquare(SKCanvas canvas, SKPaint paint)
        {
            using (SKPath path = new SKPath())
            {
                path.MoveTo(200, 50);
                path.LineTo(300, 50);
                path.LineTo(300, 150);
                path.LineTo(200, 150);
                path.Close();

                canvas.DrawPath(path, paint);
            }
        }

        // 绘制五边形
        private void DrawPentagon(SKCanvas canvas, SKPaint paint)
        {
            float centerX = 400;
            float centerY = 100;
            float radius = 50;
            int sides = 5;

            DrawRegularPolygon(canvas, paint, centerX, centerY, radius, sides);
        }

        // 绘制六边形
        private void DrawHexagon(SKCanvas canvas, SKPaint paint)
        {
            float centerX = 550;
            float centerY = 100;
            float radius = 50;
            int sides = 6;

            DrawRegularPolygon(canvas, paint, centerX, centerY, radius, sides);
        }

        // 绘制自定义多边形
        private void DrawCustomPolygon(SKCanvas canvas, SKPaint paint)
        {
            using (SKPath path = new SKPath())
            {
                // 定义多边形的顶点
                SKPoint[] points = new SKPoint[]
                {
                    new SKPoint(50, 200),   // 第一个点
                    new SKPoint(150, 200),  // 第二个点
                    new SKPoint(200, 300),  // 第三个点
                    new SKPoint(100, 350),  // 第四个点
                    new SKPoint(25, 300)    // 第五个点
                };

                // 移动到第一个点
                path.MoveTo(points[0]);

                // 连接所有点
                for (int i = 1; i < points.Length; i++)
                {
                    path.LineTo(points[i]);
                }

                path.Close(); // 闭合路径
                canvas.DrawPath(path, paint);
            }
        }

        // 通用方法：绘制正多边形
        private void DrawRegularPolygon(SKCanvas canvas, SKPaint paint, float centerX, float centerY, float radius, int sides)
        {
            using (SKPath path = new SKPath())
            {
                // 计算每个角的弧度
                float angleStep = 2 * (float)Math.PI / sides;

                // 移动到第一个点
                float firstX = centerX + radius * (float)Math.Cos(0);
                float firstY = centerY + radius * (float)Math.Sin(0);
                path.MoveTo(firstX, firstY);

                // 绘制其余的点
                for (int i = 1; i <= sides; i++)
                {
                    float angle = i * angleStep;
                    float x = centerX + radius * (float)Math.Cos(angle);
                    float y = centerY + radius * (float)Math.Sin(angle);
                    path.LineTo(x, y);
                }

                path.Close();
                canvas.DrawPath(path, paint);
            }
        }
    }
}

1. 引言

基于颜色的对象检测和计数在工业、农业、医疗等领域有着广泛的应用。借助OpenCvSharp，我们可以快速实现这类功能。本文将详细介绍如何使用C#和OpenCvSharp来实现基于颜色的对象检测和计数。

2. 应用场景

• 工业生产线上的产品计数（如不同颜色的瓶盖）
• 农业领域的水果分选计数
• 医疗领域的细胞计数
• 质量控制中的缺陷检测
• 交通监控中的车辆计数
• 零售业中的商品库存统计

3. 环境准备

C#
// 安装必要的NuGet包
// Install-Package OpenCvSharp4
// Install-Package OpenCvSharp4.runtime.win

using OpenCvSharp;
using System;

4. 基本实现流程

4.1 基础代码框架

C#
public class ColorObjectCounter
{
    private Scalar lowerBound;
    private Scalar upperBound;

    public ColorObjectCounter(Scalar lower, Scalar upper)
    {
        lowerBound = lower;
        upperBound = upper;
    }

    public int CountObjects(string imagePath)
    {
        using (var src = Cv2.ImRead(imagePath))
        {
            return CountObjects(src);
        }
    }

    public int CountObjects(Mat image)
    {
        if (image == null)
            throw new ArgumentNullException(nameof(image));

        // 1. 转换颜色空间
        using var hsvImage = new Mat();
        Cv2.CvtColor(image, hsvImage, ColorConversionCodes.BGR2HSV);

        // 2. 创建掩码
        using var mask = new Mat();
        Cv2.InRange(hsvImage, lowerBound, upperBound, mask);

        // 3. 形态学操作
        using var kernel = Cv2.GetStructuringElement(MorphShapes.Ellipse, new Size(5, 5));
        using var processedMask = new Mat();
        Cv2.MorphologyEx(mask, processedMask, MorphTypes.Open, kernel);

        // 4. 查找轮廓
        Point[][] contours;
        HierarchyIndex[] hierarchy;
        Cv2.FindContours(
            processedMask,
            out contours,
            out hierarchy,
            RetrievalModes.External,
            ContourApproximationModes.ApproxSimple);

        // 5. 过滤和计数
        return FilterAndCountContours(contours);
    }

    private int FilterAndCountContours(Point[][] contours)
    {
        int count = 0;
        foreach (var contour in contours)
        {
            double area = Cv2.ContourArea(contour);
            if (area > 100) // 面积阈值，需要根据实际情况调整
            {
                count++;
            }
        }
        return count;
    }
}

C#
static void Main(string[] args)
{
    // 调整HSV范围以更好地检测红色缝线  
    Scalar lowerRed1 = new Scalar(0, 50, 50);    // 降低饱和度和亮度的最小值  
    Scalar upperRed1 = new Scalar(10, 255, 255);

    // 创建检测器实例  
    ColorObjectCounter counter1 = new ColorObjectCounter(lowerRed1, upperRed1);

    string imagePath = "output_cropped2.jpg";

    // 调用检测方法  
    int redObjects = counter1.CountObjects(imagePath);


    Console.WriteLine($"检测到 {redObjects} 条红色线");

}

1. 简介

本文将详细介绍如何使用C#和OpenCvSharp来实现基于轮廓检测的对象计数。我们将通过多个实例来说明不同场景下的轮廓检测和计数方法。

2. 环境准备

首先需要安装必要的NuGet包：

Bash
Install-Package OpenCvSharp4
Install-Package OpenCvSharp4.Windows

4. 简单对象计数示例

4.1 基础计数

C#
static void Main(string[] args)
{
    CountClips("clip.png");

    Cv2.WaitKey(0);
    Cv2.DestroyAllWindows();
}

public static int CountClips(string imagePath)
{
    using (var src = new Mat(imagePath))
    using (var gray = new Mat())
    using (var blur = new Mat())
    using (var binary = new Mat())
    {
        // 转换为灰度图  
        Cv2.CvtColor(src, gray, ColorConversionCodes.BGR2GRAY);

        // 高斯模糊  
        Cv2.GaussianBlur(gray, blur, new Size(5, 5), 0);

        // 使用自适应阈值  
        Cv2.AdaptiveThreshold(
            blur,
            binary,
            255,
            AdaptiveThresholdTypes.GaussianC,
            ThresholdTypes.Binary,
            11,  // 邻域大小  
            2    // 常数差值  
        );

        // 查找轮廓，包括内部轮廓  
        Point[][] contours;
        HierarchyIndex[] hierarchy;
        Cv2.FindContours(
            binary,
            out contours,
            out hierarchy,
            RetrievalModes.Tree,  // 改用Tree模式  
            ContourApproximationModes.ApproxSimple);

        // 过滤轮廓  
        int clipCount = 0;
        for (int i = 0; i < contours.Length; i++)
        {

            // 计算轮廓周长  
            double perimeter = Cv2.ArcLength(contours[i], true);

                Cv2.DrawContours(
                    src,
                    contours,
                    i,
                    Scalar.Red,
                    2);
                clipCount++;
        }

        Cv2.ImShow("Result", src);
        return clipCount;
    }
}

Python
Cv2.AdaptiveThreshold(  
    blur,       // 输入图像（通常是灰度图或经过模糊处理的图像）  
    binary,     // 输出图像（二值化结果）  
    255,        // 最大值（像素被判定为白色时的值）  
    AdaptiveThresholdTypes.GaussianC,  // 自适应方法类型  
    ThresholdTypes.Binary,             // 阈值类型  
    11,         // 邻域大小（块大小）  
    2           // 常数差值（C）  
);