TilingView.cs

/*
 File: TilingView.m
 Abstract: Handles tile drawing and tile image loading.
 Version: 1.1
 
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using System;
using System.Drawing;
using MonoTouch.Foundation;
using MonoTouch.CoreAnimation;
using MonoTouch.CoreGraphics;
using MonoTouch.UIKit;
using MonoTouch.ObjCRuntime;


namespace NPhotoViewController
{
	public class TilingView : UIView
	{
		/*
		Not really sure how to approach the problem of overriding the (Class)
		'static' in the Objective-C example
		-- i.e. what I tried was WRONG [CD] see below for the correct method
		private CATiledLayer __layer;
		public override CALayer Layer {
			get 
			{	// set in ctor
				return __layer;
			}
		}	*/
		
		/// <summary>
		/// Thanks to @migueldeicaza for the _correct_ pattern to use here
		/// </summary>
		[Export ("layerClass")]
		public static Class LayerClass ()
		{
			return new Class (typeof (CATiledLayer));
		}
		
		/// <summary>
		/// initWithImageName
		/// </summary>
		public TilingView (string name, SizeF size) : base(new RectangleF(0, 0, size.Width, size.Height))
		{
			imageName = name;

			var tiledLayer = (CATiledLayer)this.Layer;
			tiledLayer.LevelsOfDetail = 4;
		}
		
		public string imageName {get;set;}
		public bool annotates {get;set;}
		
		public override void Draw (RectangleF rect)
		{
			var context = UIGraphics.GetCurrentContext();
			
			// get the scale from the context by getting the current transform matrix, then asking for
		    // its "a" component, which is one of the two scale components. We could also ask for "d".
		    // This assumes (safely) that the view is being scaled equally in both dimensions.
			var scale = context.GetCTM().xx;  // .a			// http://developer.apple.com/library/ios/#documentation/GraphicsImaging/Reference/CGAffineTransform/Reference/reference.html#//apple_ref/doc/c_ref/CGAffineTransform
			
			var tiledLayer = (CATiledLayer)this.Layer;
			var tileSize = tiledLayer.TileSize;
			
			// Even at scales lower than 100%, we are drawing into a rect in the coordinate system of the full
		    // image. One tile at 50% covers the width (in original image coordinates) of two tiles at 100%. 
		    // So at 50% we need to stretch our tiles to double the width and height; at 25% we need to stretch 
		    // them to quadruple the width and height; and so on.
		    // (Note that this means that we are drawing very blurry images as the scale gets low. At 12.5%, 
		    // our lowest scale, we are stretching about 6 small tiles to fill the entire original image area. 
		    // But this is okay, because the big blurry image we're drawing here will be scaled way down before 
		    // it is displayed.)
		    tileSize.Width /= scale;
		    tileSize.Height /= scale;
			
			// calculate the rows and columns of tiles that intersect the rect we have been asked to draw
		    int firstCol = (int)Math.Floor(rect.GetMinX() / tileSize.Width);
		    int lastCol  = (int)Math.Floor( (rect.GetMaxX()-1) / tileSize.Width);
		    int firstRow = (int)Math.Floor(rect.GetMinY() / tileSize.Height);
		    int lastRow  = (int)Math.Floor( (rect.GetMaxY()-1) / tileSize.Height);
			
		    for (int row = firstRow; row <= lastRow; row++) 
			{
		        for (int col = firstCol; col <= lastCol; col++) 
				{
		            UIImage tile = tileForScale(scale, row, col);
		            RectangleF tileRect = new RectangleF(  tileSize.Width * col
					                                     , tileSize.Height * row
					                                     , tileSize.Width
					                                     , tileSize.Height);
		
		            // if the tile would stick outside of our bounds, we need to truncate it so as to avoid
		            // stretching out the partial tiles at the right and bottom edges
		            tileRect.Intersect (this.Bounds);
		
					tile.Draw(tileRect);
		            
		            if (this.annotates)
					{
						UIColor.White.SetColor();
		                context.SetLineWidth(6.0f / scale);
		                context.StrokeRect(tileRect);
		            }
		        }
		    }
		}
		 
		public UIImage tileForScale (Single scale, int row, int col)
		{
			// we use "imageWithContentsOfFile:" instead of "imageNamed:" here because we don't want UIImage to cache our tiles
			var tileName = String.Format("Images/ImageTiles/{0}_{1}_{2}_{3}", imageName, Convert.ToInt32(scale*1000), col, row);
			//var path = NSBundle.MainBundle.PathForResource(tileName, "png");
			var path = tileName + ".png"; 	// HACK: resource paths screwed up [CD]
			UIImage image = UIImage.FromFile(path);
			return image;
		}
	}
}