/*

     File: TilingView.m

 Abstract: The main view controller for this application.

  Version: 1.3

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 */

#import "TilingView.h"

#import <QuartzCore/CATiledLayer.h>

@implementation TilingView

{

    NSString *_imageName;

}

+ (Class)layerClass

{

    return [CATiledLayer class];

}

- (id)initWithImageName:(NSString *)name size:(CGSize)size

{

    self = [super initWithFrame:CGRectMake(0, 0, size.width, size.height)];

    if (self) {

        _imageName = name;

        CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];

        tiledLayer.levelsOfDetail = 4;

    }

    return self;

}

// to handle the interaction between CATiledLayer and high resolution screens, we need to

// always keep the tiling view's contentScaleFactor at 1.0. UIKit will try to set it back

// to 2.0 on retina displays, which is the right call in most cases, but since we're backed

// by a CATiledLayer it will actually cause us to load the wrong sized tiles.

//

- (void)setContentScaleFactor:(CGFloat)contentScaleFactor

{

    [super setContentScaleFactor:1.f];

}

- (void)drawRect:(CGRect)rect

{

    CGContextRef context = UIGraphicsGetCurrentContext();

    // 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.

    CGFloat scale = CGContextGetCTM(context).a;

    CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];

    CGSize 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 = floorf(CGRectGetMinX(rect) / tileSize.width);

    int lastCol = floorf((CGRectGetMaxX(rect)-1) / tileSize.width);

    int firstRow = floorf(CGRectGetMinY(rect) / tileSize.height);

    int lastRow = floorf((CGRectGetMaxY(rect)-1) / tileSize.height);

    for (int row = firstRow; row <= lastRow; row++) {

        for (int col = firstCol; col <= lastCol; col++) {

            UIImage *tile = [self tileForScale:scale row:row col:col];

            CGRect tileRect = CGRectMake(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 = CGRectIntersection(self.bounds, tileRect);

            [tile drawInRect:tileRect];            

        }

    }

}

- (UIImage *)tileForScale:(CGFloat)scale row:(int)row col:(int)col

{

    // we use "imageWithContentsOfFile:" instead of "imageNamed:" here because we don't

    // want UIImage to cache our tiles

    //

    NSString *tileName = [NSString stringWithFormat:@"%@_%d_%d_%d", _imageName, (int)(scale * 1000), col, row];

    NSString *path = [[NSBundle mainBundle] pathForResource:tileName ofType:@"png"];

    UIImage *image = [UIImage imageWithContentsOfFile:path];

    return image;

}

@end