GDI+ Brushes

FAQ Home

1. How do I use hatched and gradient brush types?
2. How to set the rendering origin for hatch brushes?
3. How to create my own hatch styles for brushes?
 

1 How do I use hatched and gradient brush types?

The Brushes Sample shows you how to use four different brushes in several shapes. Below is a code snippet showing how to use hatched and gradient brushes.

Rectangle rect = new Rectangle(35, 190, 100, 100);
LinearGradientBrush brush2 = new LinearGradientBrush(rect,
Color.DarkOrange, Color.Aquamarine,
LinearGradientMode.ForwardDiagonal);
g.FillEllipse(brush2, 35, 190, 100, 100);

HatchBrush brush1 = new HatchBrush(HatchStyle.DiagonalCross,
Color.DarkOrange, Color.Aquamarine);
g.FillEllipse(brush1, 35, 190, 100, 100);
 

2 How to set the rendering origin for hatch brushes?

The Graphics.RenderingOrigin property lets you specify a Point structure that represents the dither origin for 8-bits-per-pixel and 16-bits-per-pixel dithering and is also used to set the origin for hatch brushes.
The following example shows how to use RenderingOrigin:

namespace Scrollable1
{
using System;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

///
/// Summary description for ScrollableControl1.
///
public class ScrollableControl1 : System.Windows.Forms.ScrollableControl
{

private void InitializeComponent ()
{
}

public ScrollableControl1()
{
InitializeComponent ();
this.AutoScrollMinSize = new Size(500, 500);
}

protected override void OnPaint(PaintEventArgs pe)
{
     pe.Graphics.RenderingOrigin = AutoScrollPosition;
HatchBrush br = new HatchBrush(HatchStyle.ForwardDiagonal, Color.Blue, Color.White);
pe.Graphics.FillRectangle(br, ClientRectangle /*or pe.ClipRectangle*/);
br.Dispose();
}
}
}
 

3 How to create my own hatch styles for brushes?

GDI+ features a TextureBrush that lets you draw repeating patterns. You can specify any bitmap to be drawn repeatedly. In this example we create bitmaps using code and attach them to a TextureBrush.

         static object[] patternSpecs = new object[]
          {
               new short[] { 0xff, 0xff, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00 }, // horizontal
               new short[] { 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc }, // vertical
               new short[] { 0x77, 0xbb, 0xdd, 0xee, 0x77, 0xbb, 0xdd, 0xee }, // \\\ Down
               new short[] { 0xee, 0xdd, 0xbb, 0x77, 0xee, 0xdd, 0xbb, 0x77 }, // /// Up
               new short[] { 0xee, 0x00, 0xee, 0xee, 0xee, 0x00, 0xee, 0xee }, // +++
          }

          public static Bitmap CreateBitmapFromPattern(int pattern)
          {
               Bitmap patternBitmap;
               IntPtr hBitmap = NativeMethods.CreateBitmap(8, 8, 1, 1, (short[]) patternSpecs[pattern]);
               if (hBitmap != IntPtr.Zero)
                    patternBitmap = Image.FromHbitmap(hBitmap);
               NativeMethods.DeleteObject(hBitmap);
               return patternBitmap;
          }

         public static void FillRectangle(Graphics g, Rectangle r, int pattern, Color foreColor, Color backColor)
          {
               Bitmap bm = CreateBitmapFromPattern(pattern);
               FillRectangle(g, r, bm, foreColor, backColor);
          }

          public static void FillRectangle(Graphics g, Rectangle r, Bitmap bm, Color foreColor, Color backColor)
          {
               if (bm != null)
               {
                    Size size = bm.PhysicalDimension.ToSize();
                    TextureBrush br = new TextureBrush(bm, new Rectangle(new Point(0, 0), size), ia);
                    br.WrapMode = WrapMode.Tile;

                    g.FillRectangle(br, r);
                    br.Dispose();
               }
          }

     public class NativeMethods
     {
          [DllImport("gdi32", CharSet=CharSet.Auto, ExactSpelling=true)]
          extern public static IntPtr CreateBitmap(int nWidth, int nHeight, int nPlanes, int nBitsPerPixel,
               [MarshalAs(UnmanagedType.LPArray)] short[] lpvBits);

          [DllImport("gdi32")]
          extern public static bool DeleteObject(IntPtr hObject) ;
     }