Nick Gravelyn

I started working on a new tile system and editor for my ninja game and realized I’m going to want the ability to change level sizes. I store my tile layouts in a basic 2D array which means that my resizing will have to do a bit of moving things around. After a little bit of work, I came up with a fairly decent (i.e. it works for my few little test cases) extension method for resizing any 2D array, including choosing where you clamp to get the same effect as Paint.NET or Photoshop when you change canvas size but get to choose where the existing data will be in relationship to the resizing.

Anyway, here’s the method. Hope this can save someone else some time. Also if you spot anything wrong about this let me know.

public enum HorizontalClamp
{
	Left,
	Right,
	Center
}

public enum VerticalClamp
{
	Top,
	Bottom,
	Center
}

public static class ArrayExtensions
{
	public static T[,] Resize<T>(
		this T[,] array,
		int newWidth,
		int newHeight,
		HorizontalClamp xClamp,
		VerticalClamp yClamp)
	{
		// get the current width and height of the array
		int width = array.GetLength(0);
		int height = array.GetLength(1);

		// start/end from the old array
		int xStart = 0, xEnd = Math.Min(width, newWidth);
		int yStart = 0, yEnd = Math.Min(height, newHeight);

		// start/end for new array
		int targetX = 0;
		int targetY = 0;

		// figure out start, end, and target coordinates.
		// no check for left or top; those are defaults.

		if (xClamp == HorizontalClamp.Right)
		{
			xStart = Math.Max(width - newWidth, 0);
			xEnd = xStart + Math.Min(width, newWidth);
			targetX = newWidth - (width - xStart);
		}
		else if (xClamp == HorizontalClamp.Center)
		{
			xStart = Math.Max(width / 2 - newWidth / 2, 0);
			xEnd = xStart + Math.Min(width, newWidth);
			targetX = Math.Max(newWidth / 2 - width / 2, 0);
		}

		if (yClamp == VerticalClamp.Bottom)
		{
			yStart = Math.Max(height - newHeight, 0);
			yEnd = yStart + Math.Min(height, newHeight);
			targetY = newHeight - (height - yStart);
		}
		else if (yClamp == VerticalClamp.Center)
		{
			yStart = Math.Max(height / 2 - newHeight / 2, 0);
			yEnd = xStart + Math.Min(height, newHeight);
			targetY = Math.Max(newHeight / 2 - height / 2, 0);
		}

		// create our return value
		T[,] newArray = new T[newWidth, newHeight];

		// copy over the values from the old array to the new array
		for (int x1 = targetX, x2 = xStart; x2 < xEnd; x1++, x2++)
		{
			for (int y1 = targetY, y2 = yStart; y2 < yEnd; y1++, y2++)
			{
				newArray[x1, y1] = array[x2, y2];
			}
		}

		return newArray;
	}
}