SkiaSharp是一个强大的跨平台2D图形绘制库，源自Google的Skia图形库。本文将深入探讨如何使用SkiaSharp绘制各种类型的直线。

基本直线绘制

C#
override protected void OnPaint(PaintEventArgs e)
{
    var info=new SKImageInfo(ClientSize.Width, ClientSize.Height);
    using (var surface = SKSurface.Create(info))
    {
        var canvas = surface.Canvas;
        canvas.Clear(SKColors.White);
        // 创建画笔（Paint）对象
        using (var paint = new SKPaint())
        {
            // 设置线条颜色为蓝色
            paint.Color = SKColors.Blue;

            // 设置线条宽度
            paint.StrokeWidth = 5;

            // 设置绘制模式为描边
            paint.Style = SKPaintStyle.Stroke;

            // 绘制从点(50, 50)到点(200, 200)的直线
            canvas.DrawLine(50, 50, 200, 200, paint);
        }
        using(var view=new SKGLControl())
        {
            // 从绘制的表面生成快照图像  
            var image = surface.Snapshot();
            // 从图像生成 SKBitmap  
            var bitmap = SKBitmap.FromImage(image);
            // 将 SKBitmap 转换为 GDI+ Bitmap，并绘制到 PaintEventArgs 的 Graphics 对象上  
            e.Graphics.DrawImage(bitmap.ToBitmap(), 0, 0);
        }
    }
}

高级直线绘制技巧

C#
override protected void OnPaint(PaintEventArgs e)
{
    var info=new SKImageInfo(ClientSize.Width, ClientSize.Height);
    using (var surface = SKSurface.Create(info))
    {
        var canvas = surface.Canvas;
        canvas.Clear(SKColors.White);
        // 创建多种风格的线条
        using (var solidLinePaint = new SKPaint())
        {
            // 实线
            solidLinePaint.Color = SKColors.Red;
            solidLinePaint.StrokeWidth = 3;
            solidLinePaint.Style = SKPaintStyle.Stroke;

            // 绘制实线
            canvas.DrawLine(50, 50, 200, 50, solidLinePaint);
        }

        using (var dashedLinePaint = new SKPaint())
        {
            // 虚线
            dashedLinePaint.Color = SKColors.Green;
            dashedLinePaint.StrokeWidth = 3;
            dashedLinePaint.Style = SKPaintStyle.Stroke;

            // 创建虚线效果
            dashedLinePaint.PathEffect = SKPathEffect.CreateDash(
                new float[] { 10, 5 },  // 10像素实线，5像素空白
                0  // 偏移量
            );

            // 绘制虚线
            canvas.DrawLine(50, 100, 200, 100, dashedLinePaint);
        }
        using (var view=new SKGLControl())
        {
            // 从绘制的表面生成快照图像  
            var image = surface.Snapshot();
            // 从图像生成 SKBitmap  
            var bitmap = SKBitmap.FromImage(image);
            // 将 SKBitmap 转换为 GDI+ Bitmap，并绘制到 PaintEventArgs 的 Graphics 对象上  
            e.Graphics.DrawImage(bitmap.ToBitmap(), 0, 0);
        }
    }
}

线条抗锯齿和高级渲染

C#
override protected void OnPaint(PaintEventArgs e)
{
    var info=new SKImageInfo(ClientSize.Width, ClientSize.Height);
    using (var surface = SKSurface.Create(info))
    {
        var canvas = surface.Canvas;
        canvas.Clear(SKColors.White);

        using (var paint = new SKPaint())
        {
            // 启用抗锯齿
            paint.IsAntialias = true;

            // 设置线帽样式
            paint.StrokeCap = SKStrokeCap.Round;  // 圆形线帽
            paint.Color = SKColors.Orange;
            paint.StrokeWidth =20;
            paint.Style = SKPaintStyle.Stroke;

            // 绘制带圆形线帽的平滑线条
            canvas.DrawLine(50, 200, 250, 200, paint);
        }
        using (var view=new SKGLControl())
        {
            // 从绘制的表面生成快照图像  
            var image = surface.Snapshot();
            // 从图像生成 SKBitmap  
            var bitmap = SKBitmap.FromImage(image);
            // 将 SKBitmap 转换为 GDI+ Bitmap，并绘制到 PaintEventArgs 的 Graphics 对象上  
            e.Graphics.DrawImage(bitmap.ToBitmap(), 0, 0);
        }
    }
}

渐变线条绘制

C#
override protected void OnPaint(PaintEventArgs e)
{
    var info=new SKImageInfo(ClientSize.Width, ClientSize.Height);
    using (var surface = SKSurface.Create(info))
    {
        var canvas = surface.Canvas;
        canvas.Clear(SKColors.White);

        // 创建线性渐变
        var shader = SKShader.CreateLinearGradient(
            new SKPoint(50, 250),   // 渐变起点
            new SKPoint(250, 250),  // 渐变终点
            new SKColor[]
            {
        SKColors.Red,    // 起始颜色
        SKColors.Blue    // 结束颜色
            },
            null,
            SKShaderTileMode.Clamp
        );

        using (var paint = new SKPaint())
        {
            paint.Shader = shader;
            paint.StrokeWidth = 20;
            paint.Style = SKPaintStyle.Stroke;

            // 绘制渐变线条
            canvas.DrawLine(50, 250, 450, 250, paint);
        }

        using (var view=new SKGLControl())
        {
            // 从绘制的表面生成快照图像  
            var image = surface.Snapshot();
            // 从图像生成 SKBitmap  
            var bitmap = SKBitmap.FromImage(image);
            // 将 SKBitmap 转换为 GDI+ Bitmap，并绘制到 PaintEventArgs 的 Graphics 对象上  
            e.Graphics.DrawImage(bitmap.ToBitmap(), 0, 0);
        }
    }
}

简单的动画

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

namespace AppLine
{
    public partial class Form1 : Form
    {
        private float dashOffset = 0;
        private Timer animationTimer;

        public Form1()
        {
            InitializeComponent();

            // 设置双缓冲，减少闪烁  
            SetStyle(ControlStyles.OptimizedDoubleBuffer |
                     ControlStyles.AllPaintingInWmPaint |
                     ControlStyles.UserPaint, true);
            UpdateStyles();

            // 初始化动画计时器  
            animationTimer = new Timer();
            animationTimer.Interval = 50; // 50毫秒更新一次  
            animationTimer.Tick += AnimationTimer_Tick;
            animationTimer.Start();
        }

        private void AnimationTimer_Tick(object sender, EventArgs e)
        {
            // 更新虚线偏移  
            dashOffset += 2;
            // 触发重绘  
            Invalidate();
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            var info = new SKImageInfo(ClientSize.Width, ClientSize.Height);
            using (var surface = SKSurface.Create(info))
            {
                var canvas = surface.Canvas;
                canvas.Clear(SKColors.White);

                using (var dashedLinePaint = new SKPaint())
                {
                    // 虚线  
                    dashedLinePaint.Color = SKColors.Green;
                    dashedLinePaint.StrokeWidth = 3;
                    dashedLinePaint.Style = SKPaintStyle.Stroke;

                    // 创建动态偏移的虚线效果  
                    dashedLinePaint.PathEffect = SKPathEffect.CreateDash(
                        new float[] { 10, 5 },  // 10像素实线，5像素空白  
                        dashOffset  // 动态偏移量  
                    );

                    // 绘制虚线  
                    canvas.DrawLine(50, 100, 500, 100, dashedLinePaint);
                }

                // 从绘制的表面生成快照图像  
                var image = surface.Snapshot();
                // 从图像生成 SKBitmap  
                var bitmap = SKBitmap.FromImage(image);
                // 将 SKBitmap 转换为 GDI+ Bitmap，并绘制到 PaintEventArgs 的 Graphics 对象上  
                e.Graphics.DrawImage(bitmap.ToBitmap(), 0, 0);
            }
        }

        // 在窗体关闭时停止计时器  
        protected override void OnFormClosing(FormClosingEventArgs e)
        {
            base.OnFormClosing(e);
            animationTimer.Stop();
        }
    }
}

性能建议

• 尽量重用SKPaint对象
• 对于复杂绘制，考虑使用SKPath
• 启用抗锯齿会略微增加性能开销

结论

SkiaSharp提供了丰富的API来绘制各种风格和类型的直线。通过灵活运用SKPaint和不同的绘制方法，您可以创建出各种精美的线条效果。

希望这篇文章能帮助您深入了解SkiaSharp中的直线绘制技术！