如何在c＃/ winforms中将图像裁剪为圆形？ [英] How to crop an image to a circle in c# / winforms?

问题描述

编辑：重复问题中给出的代码对我来说没有解决问题。

the code given in the "duplicate" question didn't solve the problem for me.

我遇到的主要问题是我可以只需使用CSS和radius，这很容易。

The main problem I'm having is that I can't simply use CSS and radius, which would be easy.

这是在winforms页面/项目中正在加载的图像。我必须尝试将正方形/矩形图像制作成圆形。我尝试了以下2种方法（结果将在每种方法下方发布）：

It's an image being loaded in, in a winforms page/project. I have to try and make a square/rectangle image into a circle. I've tried following 2 methods (results will be posted beneath each):

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;
    }
}

调用代码：

Image StartImage = Image.FromFile(medwImg);
Image RoundedImage = btn.RoundCorners(StartImage, 100, Color.Transparent);
btn.NormalImage = RoundedImage;

结果：

如果将半径值更改为145，则可以看到以下结果：

If you change the radius value to 145 you can see this result:

< a href = https://i.stack.imgur.com/Cqqyw.png rel = nofollow noreferrer>

如您所见，也不好。

这是我的第二种方法：

public Image CropToCircle(Image srcImage, Color backGround)
{
    Image dstImage = new Bitmap(srcImage.Width, srcImage.Height, srcImage.PixelFormat);
    Graphics g = Graphics.FromImage(dstImage);

    using (Brush br = new SolidBrush(backGround))
    {
        g.FillRectangle(br, 0, 0, dstImage.Width, dstImage.Height);
    }

    GraphicsPath path = new GraphicsPath();
    path.AddEllipse(0, 0, dstImage.Width, dstImage.Height);
    g.SetClip(path);
    g.DrawImage(srcImage, 0, 0);        

    return dstImage;
}

调用代码：

Image StartImage = Image.FromFile(medwImg);
Image RoundedImage = btn.CropToCircle(StartImage, Color.FromArgb(0, 101, 167));
btn.NormalImage = RoundedImage;

结果如下：

这看起来更好，但仍然不是一个完整的圆圈。

This looks better, but still isn't a nice full circle.

我的最佳猜测是第二种方法最接近一种好的解决方案，但是我不知道下一步该怎么做才能从中创建一个完整的圆

My best guess is the 2nd method is closest by to a good solution, but I don't know what to do next in order for a full circle to be created from the source image.

推荐答案

我已经使用以下方法找到了问题的答案：

I've found an answer to my problem, using following method:

// makes nice round ellipse/circle images from rectangle images
public Image ClipToCircle(Image srcImage, PointF center, float radius, Color backGround)
{
    Image dstImage = new Bitmap(srcImage.Width, srcImage.Height, srcImage.PixelFormat);

    using (Graphics g = Graphics.FromImage(dstImage))
    {
        RectangleF r = new RectangleF(center.X - radius, center.Y - radius,
                                                 radius * 2, radius * 2);

        // enables smoothing of the edge of the circle (less pixelated)
        g.SmoothingMode = SmoothingMode.AntiAlias;

        // fills background color
        using (Brush br = new SolidBrush(backGround))
        {
            g.FillRectangle(br, 0, 0, dstImage.Width, dstImage.Height);
        }

        // adds the new ellipse & draws the image again 
        GraphicsPath path = new GraphicsPath();
        path.AddEllipse(r);
        g.SetClip(path);
        g.DrawImage(srcImage, 0, 0);

        return dstImage;
    }
}

代码调用方法：

Image StartImage = Image.FromFile(medwImg);
Image RoundedImage = btn.ClipToCircle(StartImage, new PointF(StartImage.Width/2, StartImage.Height/2), StartImage.Width/2, Color.FromArgb(0, 101, 167));
btn.NormalImage = RoundedImage;

现在我得到了漂亮的圆形图像（结果）：

Now I get beautiful round images (result):

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