A code snippet to visualize the placement of cells in a UICollectionViewLayout. Stick it at the bottom of the layoutAttributesForElementsInRect: method and copy/paste the output in your terminal window and you'll something like this: http://i.imgur.com/X74mB0v.png.

gistfile1.m

    NSMutableString *magick = [[NSMutableString alloc] init];
    [magick appendString:@"xc:skyblue -fill white -stroke black "];
    
    int minX = rect.origin.x;
    int minY = rect.origin.y;
    int maxX = rect.size.width;
    int maxY = rect.size.height;
    for (UICollectionViewLayoutAttributes *att in theLayoutAttributes) {
        minX = MIN(minX, att.frame.origin.x);
        minY = MIN(minY, att.frame.origin.y);
        maxX = MAX(maxX, att.frame.origin.x + att.frame.size.width);
        maxY = MAX(maxY, att.frame.origin.y + att.frame.size.height);

        int page = att.indexPath.row / self.perPage;
        [magick appendFormat:@" -draw \"rectangle %.0f,%.0f %.0f,%.0f\" -draw \"text %.0f,%.0f '%d/%d'\"", att.frame.origin.x, att.frame.origin.y, att.frame.origin.x + att.frame.size.width, att.frame.origin.y + att.frame.size.height, att.frame.origin.x, att.frame.origin.y, att.indexPath.item, page];
    }
    [magick insertString:[NSString stringWithFormat:@"convert -size %dx%d ", maxX, maxY] atIndex:0];
    
    [magick appendFormat:@" -fill none -stroke red -draw \"rectangle %.0f,%.0f %.0f,%.0f\"", rect.origin.x, rect.origin.y, rect.origin.x+rect.size.width, rect.origin.y+rect.size.height];
    
    [magick appendFormat:@" -crop %.0fx%.0f+%.0f+%.0f +repage", rect.size.width+10, rect.size.height+10, rect.origin.x-5, rect.origin.y-5];
    
    static int count = 0;
    [magick appendFormat: @" blah%04d.png", count++];
    
    NSLog(@"magick: %@", magick);