如何在 C# 中创建带圆角的图像？

Question

我想使用 GDI+ 创建带有圆角的图像（来自另一个图像）。最好的方法是什么？

PS：它不是用于网络的，所以我不能使用客户端 CSS

Answer 1

最直接的方法是使用带圆角的可缩放蒙版。将蒙版应用于图像并导出新图像。

Here 是 CodeProject 的一篇文章，专门处理这个问题。

Answer 2

这个功能似乎做你想做的事。如果需要，它也可以很容易地修改为返回位图。您还需要清理您不再需要的任何图像等。改编自： http://www.jigar.net/howdoi/viewhtmlcontent98.aspx

using System.Drawing;
using System.Drawing.Drawing2D;

public Image RoundCorners(Image StartImage, int CornerRadius, Color BackgroundColor)
{
    CornerRadius *= 2;
    Bitmap RoundedImage = new Bitmap(StartImage.Width, StartImage.Height);
    using(Graphics g = Graphics.FromImage(RoundedImage))
    {
      g.Clear(BackgroundColor);
      g.SmoothingMode = SmoothingMode.AntiAlias;
      Brush brush = new TextureBrush(StartImage);
      GraphicsPath gp = new GraphicsPath();
      gp.AddArc(0, 0, CornerRadius, CornerRadius, 180, 90);
      gp.AddArc(0 + RoundedImage.Width - CornerRadius, 0, CornerRadius, CornerRadius, 270, 90);
      gp.AddArc(0 + RoundedImage.Width - CornerRadius, 0 + RoundedImage.Height - CornerRadius, CornerRadius, CornerRadius, 0, 90);
      gp.AddArc(0, 0 + RoundedImage.Height - CornerRadius, CornerRadius, CornerRadius, 90, 90);
      g.FillPath(brush, gp);
      return RoundedImage;
    }
}

Image StartImage = Image.FromFile("YourImageFile.jpg");
Image RoundedImage = this.RoundCorners(StartImage, 25, Color.White);
//Use RoundedImage...

Answer 3

使用 Graphics.SetClip() 方法是最好的方法。例如：

    public static Image OvalImage(Image img) {
        Bitmap bmp = new Bitmap(img.Width, img.Height);
        using (GraphicsPath gp = new GraphicsPath()) {
            gp.AddEllipse(0, 0, img.Width, img.Height);
            using (Graphics gr = Graphics.FromImage(bmp)) {
                gr.SetClip(gp);
                gr.DrawImage(img, Point.Empty);
            }
        }
        return bmp;
    }

Answer 4

所有其他答案都存在沿左边框和上边框 1 像素失真的问题。此代码通过在为蒙版添加弧时在左侧和顶部偏移 -1 个像素来解决此问题。

public static Image RoundCorners(Image StartImage, int CornerRadius, Color BackgroundColor)
{
    CornerRadius *= 2;
    Bitmap RoundedImage = new Bitmap(StartImage.Width, StartImage.Height);

    using(Graphics g = Graphics.FromImage(RoundedImage))
    {
       g.Clear(BackgroundColor);
       g.SmoothingMode = SmoothingMode.HighQuality;
       g.CompositingQuality = CompositingQuality.HighQuality;
       g.InterpolationMode = InterpolationMode.HighQualityBicubic;

       using(Brush brush = new TextureBrush(StartImage))
       {
          using(GraphicsPath gp = new GraphicsPath())
          {
             gp.AddArc(-1, -1, CornerRadius, CornerRadius, 180, 90);
             gp.AddArc(0 + RoundedImage.Width - CornerRadius, -1, CornerRadius, CornerRadius, 270, 90);
             gp.AddArc(0 + RoundedImage.Width - CornerRadius, 0 + RoundedImage.Height - CornerRadius, CornerRadius, CornerRadius, 0, 90);
             gp.AddArc(-1, 0 + RoundedImage.Height - CornerRadius, CornerRadius, CornerRadius, 90, 90);

             g.FillPath(brush, gp);
          }
       }

       return RoundedImage;
    }
}

Answer 5

我最终结合了https://stackoverflow.com/a/1759073 和https://stackoverflow.com/a/1759225 来获得圆形图像，因为我希望背景是透明的。想我会分享它：

private Image RoundCorners(Image image, int cornerRadius)
{
    cornerRadius *= 2;
    Bitmap roundedImage = new Bitmap(image.Width, image.Height);
    GraphicsPath gp = new GraphicsPath();
    gp.AddArc(0, 0, cornerRadius, cornerRadius, 180, 90);
    gp.AddArc(0 + roundedImage.Width - cornerRadius, 0, cornerRadius, cornerRadius, 270, 90);
    gp.AddArc(0 + roundedImage.Width - cornerRadius, 0 + roundedImage.Height - cornerRadius, cornerRadius, cornerRadius, 0, 90);
    gp.AddArc(0, 0 + roundedImage.Height - cornerRadius, cornerRadius, cornerRadius, 90, 90);
    using (Graphics g = Graphics.FromImage(roundedImage))
    {
        g.SmoothingMode = SmoothingMode.HighQuality;
        g.SetClip(gp);
        g.DrawImage(image, Point.Empty);
    }
    return roundedImage;
}

Answer 6

盘旋时边缘更平滑。

public static Image RoundCorners(Image StartImage, float CornerRadius, Color BackgroundColor)
{
    CornerRadius *= 2;
    Bitmap RoundedImage = new Bitmap(StartImage.Width, StartImage.Height);

    using(Graphics g = Graphics.FromImage(RoundedImage))
    {
       g.Clear(BackgroundColor);
       g.SmoothingMode = SmoothingMode.HighQuality;
       g.CompositingQuality = CompositingQuality.HighQuality;
       g.InterpolationMode = InterpolationMode.HighQualityBicubic;

       using(Brush brush = new TextureBrush(StartImage))
       {
          using(GraphicsPath gp = new GraphicsPath())
          {
            gp.AddArc(0, -1, CornerRadius, CornerRadius, 180, 90);
            gp.AddArc(-1 + RoundedImage.Width - CornerRadius, -1, CornerRadius, CornerRadius, 270, 90);
            gp.AddArc(-1 + RoundedImage.Width - CornerRadius, -1 + RoundedImage.Height - CornerRadius, CornerRadius, CornerRadius, 0, 90);
            gp.AddArc(0, -1 + RoundedImage.Height - CornerRadius, CornerRadius, CornerRadius, 90, 90);

             g.FillPath(brush, gp);
          }
       }

       return RoundedImage;
    }
}