Help with System.Drawing.Region & System.Drawing.Bitmap

[Magiaus]

What I am trying to do is make a routine that take a System.Drawing.Color and a System.Drawing.Bitmap in and returns a region excluding the passed in color. Sounds kinda easy. At least I thought so..... I have overflow in System.Drawing.dll......

public System.Drawing.Region ToRegion(System.Drawing.Color color, System.Drawing.Bitmap image)
{
	System.Drawing.Color c;
    	System.Drawing.Region r1 = null;
    	System.Drawing.Region r2 = null;

    	int[] colors = new int[] {System.Drawing.ColorTranslator.ToWin32(color),0}
    
	for(int x = 0; x < image.Width; x++)
    	{
        	for(int y = 0; y < image.Height; y++)
        	{
                	c = image.GetPixel(x, y);
                	colors[1] = System.Drawing.ColorTranslator.ToWin32(c);
                	if(color[0] != color[1])
                	{
                        	if(r1 == null)
                        	{
                                	r1 = new System.Drawing.Region(new System.Drawing.Rectangle(x, y, x + 1, y + 1));
                        	}
                        	else
                        	{
                               		r2 = new System.Drawing.Region(new System.Drawing.Rectangle(x, y, x + 1, y + 1));
                               		r1.Union(r2); //I'm not sure on this either
                        	}
                	}
        	}
    	}
    	return r1;
}

As far as I can tel that code should work and it returns with no errors, BUT when you go say

frm.Region = ToRegion(System.Drawing.Color.Black, imgIGotFromFile);

it runs, and runs, and runs, and System.OverFlowExeption in system.drawing.dll

I also tried GrapicsPath.AddRectangle and the contructing a Region from the path but same overflow error.

I don't want to use API if I can avoid it. Especially since it should work in the framework. I have vb6 code just like this using Region Api and SetWindowRgn that works......

Help!!!!

[Pirate]

Are you calling this in OnPaint or something that redraws UI ?

[Magiaus]

No right now I call it in a form that creates a test form.

Form frm = new Form();
Region r = ToRegion(Color.Black, imageFromAFile);
frm.Region = r;

I get r fine but the frm.Region = r causes overflow and to be honest I can't find a way to validate r very well.....

[Pirate]

I don't know and or at least I can't test this but you may try replacing these (x, y) in r1 with numbers . Otherwise , I've got no clue .

[Magiaus]

Me either but I'm thinking about it....

[Magiaus]

this code is actualy not all full of errors

namespace Ezekiel.Windows.Forms
{
	/// <summary>
	/// Collection of usefull functions.
	/// </summary>
	public class Helpers
	{
		/// <summary>
		/// Helper methods for System.Drawing.Regions.
		/// </summary>
		public class Region
		{
			/// <summary>
			/// Gets a System.Drawing.Region equal to <paramref name="image"/> excluding <paramref name="excludeColor"/>.
			/// </summary>
			/// <param name="excludeColor">System.Drawing.Color to exclude from the generated System.Drawing.Region.</param>
			/// <param name="image">System.Drawing.Bitmap the the generated System.Drawing.Region will equal ecluding <paramref name="excludeColor"/></param>
			/// <returns>System.Drawing.Region equal to <paramref name="image"/> excluding <paramref name="excludeColor"/>.</returns>
			public static System.Drawing.Region FromBitmap(System.Drawing.Color excludeColor, System.Drawing.Bitmap image)
			{
				System.Drawing.Color c;
				System.Drawing.Region r1 = null;
				System.Drawing.Region r2 = null;

				int[] colors = new int[] {System.Drawing.ColorTranslator.ToWin32(excludeColor),0};
    
				for(int x = 0; x < image.Width; x++)
				{
					for(int y = 0; y < image.Height; y++)
					{
						c = image.GetPixel(x, y);
						colors[1] = System.Drawing.ColorTranslator.ToWin32(c);
						if(colors[0] != colors[1])
						{
							if(r1 == null)
							{
								r1 = new System.Drawing.Region(new System.Drawing.Rectangle(x, y, x + 1, y + 1));
							}
							else
							{
								r2 = new System.Drawing.Region(new System.Drawing.Rectangle(x, y, x + 1, y + 1));
								r1.Union(r2); //I'm not sure on this either
							}
						}
					}
				}
				return r1;
			}
		}
	}
}

[Magiaus]

I hate not being able to make something work. I haven't slept since I started this because my brain won't shut up about why won't it work.....