How to create image with rounded corners in C#?

I'd like to create image (from another one) with rounded corners with GDI+. What's the best way to do this?

PS: it's not f开发者_JAVA百科or web, so I cannot make use of client CSS

This function seems to do what you want. It can also easily be modified to return a Bitmap if needed. You'll also need to clean up any images you no longer want, etc.. Adapted from: 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...

Using the Graphics.SetClip() method is the best way. For example:

    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;
    }

The most straightforward way would be to use a scalable mask with rounded corners. Apply the mask to the image and export the new image.

Here is a CodeProject article dealing with precisely that.

I ended up combining both https://stackoverflow.com/a/1759073 and https://stackoverflow.com/a/1759225 to get my rounded images, as I wanted the background to be transparent. Thought I'd share it:

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;
}

All the other answers suffer from a problem with a 1 pixel distortion along the left and top border. This code fixes the problem by offsetting -1 pixels in the left and top when adding the arcs for the mask.

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;
    }
}

Smoother edges when circling.

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;
    }
}