Is it possible to have anti-aliasing when drawing a cropped image?

Question

Currently, I am successfully using the classGraphics to draw a non-rectangular clipped image (turtle inside):

My code looks something like this:

using (var g = Graphics.FromImage(image))
{
    g.InterpolationMode = InterpolationMode.HighQualityBicubic;

    using (var gfxPath = new GraphicsPath())
    {
        gfxPath.AddEllipse(r);

        using (var region = new Region(r))
        {
            region.Exclude(gfxPath);

            g.ExcludeClip(region);

            g.DrawImage(turtleImage, r, r2, GraphicsUnit.Pixel);
        }
    }
}

It all works as expected. What I do not know how to solve is to make the border of the image smoothed.

The enlarged image looks like this:

Those. the border where the image ends and the transparent “background” of the image begins is draft, not smooth alpha blending.

My question is:

Can I crop a drawn image and activate anti-aliasing?

Answer 1

, :

http://danbystrom.se/2008/08/24/soft-edged-images-in-gdi/

, , GraphicsPath . - :

Rectangle outerRect = ClientRectangle;
Rectangle rect = Rectangle.Inflate(outerRect, -20, -20);

using (Image img = new Bitmap("test.jpg"))
{
    g.DrawImage(img, outerRect);

    using (SolidBrush brush = new SolidBrush(Color.White))
    using (GraphicsPath path = new GraphicsPath())
    {
        g.SmoothingMode = SmoothingMode.AntiAlias;

        path.AddEllipse(rect);
        path.AddRectangle(outerRect);

        g.FillPath(brush, path);
    }
}

Answer 2

, . , . . .

    /// <summary>Redimensiona y recorta la imagen en forma de Circulo (con Antialias).</summary>
    /// <param name="srcImage">Imagen Original a Recortar</param>
    /// <param name="size">Tamaño deseado (en pixeles)</param>
    /// <param name="BackColor">Color de fondo</param>
    public static Image CropToCircle(System.Drawing.Image srcImage, Size size, System.Drawing.Color BackColor)
    {
        System.Drawing.Image Canvas = new System.Drawing.Bitmap(size.Width, size.Height, srcImage.PixelFormat);
        System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(Canvas);

        System.Drawing.Rectangle outerRect = new System.Drawing.Rectangle(-1, -1, Canvas.Width + 1, Canvas.Height + 1);
        System.Drawing.Rectangle rect = System.Drawing.Rectangle.Inflate(outerRect, -2, -2);

        g.DrawImage(srcImage, outerRect);

        using (System.Drawing.SolidBrush brush = new System.Drawing.SolidBrush(BackColor))
        using (System.Drawing.Drawing2D.GraphicsPath path = new System.Drawing.Drawing2D.GraphicsPath())
        {
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
            g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
            g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;

            path.AddEllipse(rect);
            path.AddRectangle(outerRect);

            g.FillPath(brush, path);
        }

        return Canvas;
    }

: ( 64x64 )

    System.Drawing.Image img = System.Drawing.Image.FromFile(@"E:\Mis Documentos\Mis imágenes\ergo-proxy-fullon-fight.jpg");
    System.Drawing.Image circle = Util.CropToCircle(img, new System.Drawing.Size(64,64), System.Drawing.Color.White);
    if (circle != null)
    {
        this.picUser.Image = circle;
    }

Answer 3

, , - .

, (, SetClip), .

, , , , . .

:

/// <summary>
/// Crop the given image into a circle (or ellipse, if the image isn't square)
/// </summary>
/// <param name="img">The image to modify</param>
/// <returns>The new, round image</returns>
private static Bitmap CropCircle(Image img) {
    var roundedImage = new Bitmap(img.Width, img.Height, img.PixelFormat);

    using (var g = Graphics.FromImage(roundedImage))
    using (var gp = new GraphicsPath()) {
        g.Clear(Color.Transparent);

        g.SmoothingMode = SmoothingMode.AntiAlias;

        Brush brush = new TextureBrush(img);
        gp.AddEllipse(0, 0, img.Width, img.Height);
        g.FillPath(brush, gp);
    }

    return roundedImage;
}

. , .

Answer 4

I had the same problem with building a circular profile with a transparent background. The tactic that I finally settled on was to resize the image to an arbitrary multiple (in my case 5x), perform a clipping operation, and then collapse it to its original size using SmoothingMode.AntiAlias. I get a beautiful feathered line in the picture.

Is it a hack? Yes. Is this a performer? Mmm, probably not. It works? Fine!