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POCATiledLayer and not rendered slices
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  1. POCATiledLayer and not rendered slices
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    copied!<p><strong>The problem:</strong></p> <p>I've to render a big image 7148x15000px (a custom map), so i've looking around for something usefull and i've found <a href="http://www.cimgf.com/2011/03/01/subduing-catiledlayer/" rel="nofollow">BitmapSlice</a>, but the problem is that the very first time i run the app (on device and simulator) several slices aren't loaded correctly and i see the image with large black holes.</p> <p><strong>Code:</strong></p> <p>BitmapSliceViewController.h</p> <pre><code>#import &lt;UIKit/UIKit.h&gt; @interface BitmapSliceViewController : UIViewController&lt;UIScrollViewDelegate&gt; @property (nonatomic, retain) UIImageView *_zoomView; @property (nonatomic, retain) IBOutlet UIScrollView *scrollView; - (void)saveTilesOfSize:(CGSize)size forImage:(UIImage*)image toDirectory (NSString*)directoryPath usingPrefix:(NSString*)prefix; @end </code></pre> <p>BitmapSliceViewController.m</p> <pre><code>#import "BitmapSliceViewController.h" #import "TileView.h" @implementation BitmapSliceViewController @synthesize scrollView; - (void)dealloc { [super dealloc]; } - (void)viewDidUnload { [super viewDidUnload]; } - (void)viewDidLoad { [super viewDidLoad]; NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); NSString *directoryPath = [paths objectAtIndex:0]; dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ UIImage *big = [UIImage imageNamed:@"map.jpg"]; [self saveTilesOfSize:(CGSize){256, 256} forImage:big toDirectory:directoryPath usingPrefix:@"map_"]; dispatch_async(dispatch_get_main_queue(), ^{ [scrollView setNeedsDisplay]; }); }); TileView *tv = [[TileView alloc] initWithFrame:(CGRect){{0,0}, (CGSize){7148,15000}}]; [tv setTileTag:@"map_"]; [tv setTileDirectory:directoryPath]; [scrollView addSubview:tv]; [scrollView setContentSize:(CGSize){7148,15000}]; [scrollView setDelegate:self]; } - (void)saveTilesOfSize:(CGSize)size forImage:(UIImage*)image toDirectory:(NSString*)directoryPath usingPrefix:(NSString*)prefix { CGFloat cols = [image size].width / size.width; CGFloat rows = [image size].height / size.height; int fullColumns = floorf(cols); int fullRows = floorf(rows); CGFloat remainderWidth = [image size].width - (fullColumns * size.width); CGFloat remainderHeight = [image size].height - (fullRows * size.height); if (cols &gt; fullColumns) fullColumns++; if (rows &gt; fullRows) fullRows++; CGImageRef fullImage = [image CGImage]; for (int y = 0; y &lt; fullRows; ++y) { for (int x = 0; x &lt; fullColumns; ++x) { CGSize tileSize = size; if (x + 1 == fullColumns &amp;&amp; remainderWidth &gt; 0) { // Last column tileSize.width = remainderWidth; } if (y + 1 == fullRows &amp;&amp; remainderHeight &gt; 0) { // Last row tileSize.height = remainderHeight; } CGImageRef tileImage = CGImageCreateWithImageInRect(fullImage, (CGRect){{x*size.width, y*size.height}, tileSize}); NSData *imageData = UIImageJPEGRepresentation([UIImage imageWithCGImage:tileImage], 1); CGImageRelease(tileImage); NSString *path = [NSString stringWithFormat:@"%@/%@%d_%d.png", directoryPath, prefix, x, y]; [imageData writeToFile:path atomically:NO]; } } } @end </code></pre> <p>TileView.h</p> <pre><code>@interface TileView : UIView @property (nonatomic, copy) NSString *tileTag; @property (nonatomic, copy) NSString *tileDirectory; - (UIImage*)tileAtCol:(int)col row:(int)row; @end </code></pre> <p>TileView.m</p> <pre><code>#import "TileView.h" @implementation TileView @synthesize tileTag; @synthesize tileDirectory; + layerClass { return [CATiledLayer class]; } - (id)initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; if (!self) return nil; return self; } - (void)dealloc { [super dealloc]; } - (void)drawRect:(CGRect)rect { //CGContextRef context = UIGraphicsGetCurrentContext(); CGSize tileSize = (CGSize){256, 256}; 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 &lt;= lastRow; row++) { for (int col = firstCol; col &lt;= lastCol; col++) { UIImage *tile = [self tileAtCol:col row:row]; if (tile) { CGRect tileRect = CGRectMake(tileSize.width * col, tileSize.height * row, tileSize.width, tileSize.height); tileRect = CGRectIntersection(self.bounds, tileRect); [tile drawInRect:tileRect]; // [[UIColor whiteColor] set]; // CGContextSetLineWidth(context, 6.0); // CGContextStrokeRect(context, tileRect); } } } } - (UIImage*)tileAtCol:(int)col row:(int)row { NSString *path = [NSString stringWithFormat:@"%@/%@%d_%d.png", tileDirectory, tileTag, col, row]; return [UIImage imageWithContentsOfFile:path]; } @end </code></pre> <p>This is the main code of the app, you can download the entire example from the site linked on the top of the post.</p> <p>As i said the main problem is the rendering of some slices that fail in the first run of the app, other runs seem works correctly.</p> <p>modifing a bit <code>- (UIImage*)tileAtCol:(int)col row:(int)row</code> </p> <pre><code>- (UIImage*)tileAtCol:(int)col row:(int)row { NSString *path = [NSString stringWithFormat:@"%@/%@%d_%d.png", tileDirectory, tileTag, col, row]; UIImage *img = [UIImage imageWithContentsOfFile:path]; if (img) { NSLog(@"good"); } else { NSLog(@"bad"); } return img; } </code></pre> <p>The problem seems to be here...</p> <p>Any ideas to fix it?</p> <p>Thanks in advance</p>
 

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