System Drawing Invert Region build out of Path

问题

Ive got a panel and im drawing a heart on that panel.. But i dont want to draw the heart i want to draw everything except the heart so the heart is transparent. Can i invert the Region selected out of the Path?

System.Drawing.Drawing2D.GraphicsPath path = new System.Drawing.Drawing2D.GraphicsPath();
            path.AddArc(0, 0, (this.Width / 2), (this.Height / 2), 135, 195);
            path.AddArc((this.Width / 2), 0, (this.Width / 2), (this.Height / 2), 210, 195);
            path.AddLine((this.Width / 2), this.Height, (this.Width / 2), this.Height);
            this.Region = new Region(path);
            this.BackColor = Color.Black;

What it looks like(white = transparent):

What i want it to look like(white = transparent):

回答1:

I think you can just add 2 graphics paths together.

You could try this code out:

private void panel1_Paint(object sender, PaintEventArgs e)
{
    GraphicsPath path = new GraphicsPath();
    path.AddArc(0, 0, (this.Width / 2), (this.Height / 2), 135, 195);
    path.AddArc((this.Width / 2), 0, (this.Width / 2), (this.Height / 2), 210, 195);
    path.AddLine((this.Width / 2), this.Height, (this.Width / 2), this.Height);

    GraphicsPath path2 = new GraphicsPath();
    path2.AddRectangle(new Rectangle(new Point(0, 0), panel1.Size));

    path2.AddPath(path, false);

    e.Graphics.FillPath(Brushes.Black, path2);
}

Result is:

回答2:

You can try excluding a region from from the Graphic object of your panel's Paint event:

GraphicsPath path = new GraphicsPath();
path.AddArc(0, 0, (this.Width / 2), (this.Height / 2), 135, 195);
path.AddArc((this.Width / 2), 0, (this.Width / 2), (this.Height / 2), 210, 195);
path.AddLine((this.Width / 2), this.Height, (this.Width / 2), this.Height);

using (Region r = new Region(path)) {
  e.Graphics.ExcludeClip(r);
}

// continue drawing...
e.Graphics.Clear(Color.Yellow);

or if trying to modify the control's region, then just use the Region's Exclude property:

GraphicsPath path = new GraphicsPath();
path.AddArc(0, 0, (this.Width / 2), (this.Height / 2), 135, 195);
path.AddArc((this.Width / 2), 0, (this.Width / 2), (this.Height / 2), 210, 195);
path.AddLine((this.Width / 2), this.Height, (this.Width / 2), this.Height);

Region r = new Region(new Rectangle(Point.Empty, this.ClientSize));
r.Exclude(path);

this.Region = r;

回答3:

I don't know of a way to invert the selection, but you can always draw a heart in the background color, then change the background color to black.

this.BackColor = Form.BackColor;
Form.BackColor = Color.Black;

回答4:

Original solution here. I've modified that for your needs

 this.Region = InvertRegion(new Region(path), this.Width, this.Height);

and

private Region InvertRegion(Region region, int width, int height)
{
    Bitmap mask = new Bitmap(width, height);
    Graphics.FromImage(mask).FillRegion(Brushes.Black, region);

    int matchColor = Color.Black.ToArgb();

    Region inverted = new System.Drawing.Region();
    inverted.MakeEmpty();
    Rectangle rc = new Rectangle(0, 0, 0, 0);
    bool inimage = false;
    for (int y = 0; y < mask.Height; y++)
    {
        for (int x = 0; x < mask.Width; x++)
        {
            if (!inimage)
            {
                if (mask.GetPixel(x, y).ToArgb() != matchColor)
                {
                    inimage = true;
                    rc.X = x;
                    rc.Y = y;
                    rc.Height = 1;
                }
            }
            else
            {
                if (mask.GetPixel(x, y).ToArgb()  == matchColor)
                {
                    inimage = false;
                    rc.Width = x - rc.X;
                    inverted.Union(rc);
                }
            }

        }
        if (inimage)
        {
            inimage = false;
            rc.Width = mask.Width - rc.X;
            inverted.Union(rc);
        }
    }
    return inverted;
}

来源：https://stackoverflow.com/questions/13039699/system-drawing-invert-region-build-out-of-path

标签

winforms

drawing