cglayer - Developer IT

CGLayer from an IUView

- by ZeLegolas

Hi On iPhone or iPad someone know how we can get a CGLayer (not a CALayer) from an UIView? Regards

Struggling to "clear" a CGLayer -- can it even be done?

So I'm doing this repetitively - making a CGLayer, doing some processing, and then releasing it. This happens a lot in real time -- so surely there is a lot of overhead in making a whole new CGLayer each time? Surely it would be better to just keep lair around, and start fresh each time? However, I do not know any way, at all, to "erase" or "start from blank" a CGLayer?? Can anyone help on this? There is a function CGContextBeginPath(cc) but it's confusing: it seems to only clear out "that" path, it does not erase all of the CGLayer back to a blank canvas. how to return a CGLayer to a blank canvas????? Does anyone know? CGLayerRef lair = CGLayerCreateWithContext( UIGraphicsGetCurrentContext(), CGSizeMake(1024,768), NULL); CGContextRef cc = CGLayerGetContext(ether); // various processing here CGContextAddPath(cc, somePath); // various processing here CGLayerRelease(lair); Any ideas?!

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How do I create a CGlayer that has an image drawn to it?

- by Jaba

I just need to know hot to create a CGLayer that has an image drawn to it. I am not completely understanding the documentation entirely. Thanks

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iPhone SDK: Rendering a CGLayer into an image object

- by codemercenary

Hi all, I am trying to add a curved border around an image downloaded and to be displayed in a UITableViewCell. In the large view (ie one image on the screen) I have the following: productImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:product.image]]; [productImageView setAlpha:0.4]; productImageView.frame = CGRectMake(10.0, 30.0, 128.0, 128.0); CALayer *roundedlayer = [productImageView layer]; [roundedlayer setMasksToBounds:YES]; [roundedlayer setCornerRadius:7.0]; [roundedlayer setBorderWidth:2.0]; [roundedlayer setBorderColor:[[UIColor darkGrayColor] CGColor]]; [self addSubview:productImageView]; In the table view cell, to get it to scroll fast, an image needs to be drawn in the drawRect method of a UIView which is then added to a custom cell. so in drawRect - (void)drawRect:(CGRect)rect { ... point = CGPointMake(boundsX + LEFT_COLUMN_OFFSET, UPPER_ROW_TOP); //CALayer *roundedlayer = [productImageView layer]; //[roundedlayer setMasksToBounds:YES]; //[roundedlayer setCornerRadius:7.0]; //[roundedlayer setBorderWidth:2.0]; //[roundedlayer setBorderColor:[[UIColor darkGrayColor] CGColor]]; //[productImageView drawRect:CGRectMake(boundsX + LEFT_COLUMN_OFFSET, UPPER_ROW_TOP, IMAGE_WIDTH, IMAGE_HEIGHT)]; // [productImageView.image drawInRect:CGRectMake(boundsX + LEFT_COLUMN_OFFSET, UPPER_ROW_TOP, IMAGE_WIDTH, IMAGE_HEIGHT)]; So this works well, but if I remove the comment and try to show the rounded CA layer the scrolling goes really slow. To fix this I suppose I would have to render this image context into a different image object, and store this in an array, then set this image as something like: productImageView.image = (UIImage*)[imageArray objectAtIndex:indexPath.row]; My question is "How do I render this layer into an image?" TIA.

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Simple iPhone drawing app with Quartz 2D

- by Mr guy 4

I am making a simple iPhone drawing program as a personal side-project. I capture touches event in a subclassed UIView and render the actual stuff to a seperate CGLayer. After each render, I call [self setNeedsLayout] and in the drawRect: method I draw the CGLayer to the screen context. This all works great and performs decently for drawing rectangles. However, I just want a simple "freehand" mode like a lot of other iPhone applications have. The way I thought to do this was to create a CGMutablePath, and simply: CGMutablePathRef path; -(void)touchBegan { path = CGMutablePathCreate(); } -(void)touchMoved { CGPathMoveToPoint(path,NULL,x,y); CGPathAddLineToPoint(path,NULL,x,y); } -(void)drawRect:(CGContextRef)context { CGContextBeginPath(context); CGContextAddPath(context,path); CGContextStrokePath(context); } However, after drawing for more than 1 second, performance degrades miserably. I would just draw each line into the off-screen CGLayer, if it were not for variable opacity! The less-than-100% opacity causes dots to be left on the screen connecting the lines. I have looked at CGContextSetBlendingMode() but alas I cannot find an answer. Can anyone point me in the right direction? Other iPhone apps are able to do this with very good efficiency.

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