CODEWITHSUNDEEP
c#.netgdi+gdigraphicspath
Matthew Layton
Matthew Layton

Reputation: 42239

GraphicsPath and DrawPath - Removing Intersecting Lines

The following code draws a cross:

using (SolidBrush brush = new SolidBrush(Color.FromArgb(192, 99, 104, 113)))
{
    using(GraphicsPath path = new GraphicsPath())
    {
        path.AddRectangle(new Rectangle(e.ClipRectangle.X + (e.ClipRectangle.Width - 40) / 2, e.ClipRectangle.Y, 40, e.ClipRectangle.Height));
        path.AddRectangle(new Rectangle(e.ClipRectangle.X, e.ClipRectangle.Y + (e.ClipRectangle.Height - 40) / 2, e.ClipRectangle.Width, 40));
        path.FillMode = FillMode.Winding;
        e.Graphics.DrawPath(Pens.DimGray, path);
    }
}

enter image description here

I would like to draw it like so:

enter image description here

I've tried using Flatten(); and CloseAllFigures(); but these don't work.

I'm looking for an effect like Union:

enter image description here

Is this possible with GraphicsPath?

Upvotes: 4

Views: 3262

Answers (4)

Tate_nn
Tate_nn

Reputation: 26

It is possible to use Regions.But you should use the API FrameRgn in GDI to draw the frame of the region if there is no other solutions.

        Graphics g = e.Graphics;
        using (SolidBrush brush = new SolidBrush(Color.FromArgb(192, 99, 104, 113)))
        {
            using (GraphicsPath path = new GraphicsPath())
            {
                path.AddRectangle(new Rectangle(e.ClipRectangle.X + (e.ClipRectangle.Width - 40) / 2, e.ClipRectangle.Y, 40, e.ClipRectangle.Height));
                path.AddRectangle(new Rectangle(e.ClipRectangle.X, e.ClipRectangle.Y + (e.ClipRectangle.Height - 40) / 2, e.ClipRectangle.Width, 40));
                path.FillMode = FillMode.Winding;
                using (Region region = new Region(path))
                {
                    IntPtr reg = region.GetHrgn(g);
                    IntPtr hdc = g.GetHdc();
                    IntPtr brushPtr = Win32.GetStockObject(Win32.WHITE_BRUSH);
                    IntPtr oldbrushPtr = Win32.SelectObject(hdc, brushPtr);
                    Win32.FrameRgn(hdc, reg, brushPtr, 1, 1);
                    Win32.DeleteObject(brushPtr);
                    Win32.SelectObject(hdc, oldbrushPtr);
                    region.ReleaseHrgn(reg);
                    g.ReleaseHdc();
                }
            }
        }

Upvotes: 1

Artail
Artail

Reputation: 133

You will need to use Regions for this, here is an example adapted from your existing code. It should be noted that you can also call Exclude, Intersect, and Xor on the region! :)

    private void Form1_Paint(object sender, PaintEventArgs e)
    {
        GraphicsPath Shape1 = new GraphicsPath();
        Shape1.AddRectangle(new Rectangle(e.ClipRectangle.X + (e.ClipRectangle.Width - 40) / 2, e.ClipRectangle.Y, 40, e.ClipRectangle.Height));

        GraphicsPath Shape2 = new GraphicsPath();
        Shape2.AddRectangle(new Rectangle(e.ClipRectangle.X, e.ClipRectangle.Y + (e.ClipRectangle.Height - 40) / 2, e.ClipRectangle.Width, 40));

        Region UnitedRegion = new Region();
        UnitedRegion.MakeEmpty();
        UnitedRegion.Union(Shape1);
        UnitedRegion.Union(Shape2);

        e.Graphics.FillRegion(Brushes.Black, UnitedRegion);
    }

Upvotes: 0

Vano Maisuradze
Vano Maisuradze

Reputation: 5899

I know this is not a perfect solution, but take it as one option:

        using (SolidBrush brush = new SolidBrush(Color.FromArgb(192, 99, 104, 113)))
        {
            using (GraphicsPath path = new GraphicsPath())
            {
                var rect1 = new Rectangle(e.ClipRectangle.X + (e.ClipRectangle.Width - 40) / 2, e.ClipRectangle.Y, 40, e.ClipRectangle.Height - 1);
                var rect2 = new Rectangle(e.ClipRectangle.X, e.ClipRectangle.Y + (e.ClipRectangle.Height - 40) / 2, e.ClipRectangle.Width - 1, 40);
                path.AddRectangle(rect1);
                path.AddRectangle(rect2);
                e.Graphics.DrawPath(Pens.DimGray, path);

                var bgRect1 = new Rectangle(rect1.X + 1, rect1.Y + 1, rect1.Width - 1, rect1.Height - 1);
                var bgRect2 = new Rectangle(rect2.X + 1, rect2.Y + 1, rect2.Width - 1, rect2.Height - 1);
                using (GraphicsPath backgroundPath = new GraphicsPath())
                {
                    backgroundPath.AddRectangle(bgRect1);
                    backgroundPath.AddRectangle(bgRect2);
                    e.Graphics.FillPath(Brushes.White, backgroundPath);
                }
            }
        }

This is the result:

This is the result

Upvotes: 1

bokibeg
bokibeg

Reputation: 2142

It's possible and what you're after is regions. Take a look at:

Regions in GDI+

I'm guessing your next step would be to outline the region. This is the difficult part because there's no API to do that. Easiest approach is to:

  • Draw everything as you have done in the first pic with a thicker pen.
  • Create regions out of the paths and union resulting regions.
  • Fill or delete the resulting union region (there is API for that).

This would produce the second picture you attached. Region operations require a bit of creativity due to the lack of edge-detect, contours or region-to-path APIs to help you draw the result.

Upvotes: 0

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