core-graphics

My app crashes when my ViewController gets deallocated while my CATiledLayer is retrieving the image to draw in a background thread. I get a message -[MyViewController respondsToSelector:]: message sent to deallocated instance 0x8f58e00 and the debugger shows 0 ___forwarding___ 1 __forwarding_prep_0__ 2 -[CATiledLayer(CATiledLayerPrivate) canDrawRect:levelOfDetail:] 3 tiled_layer_render 4 CAImageProviderThread 5 CAImageProviderBackgroundThread 6 CA::DispatchGroup::thread 7 thread_fun 8 _pthread_start Now, I do want to release that certain instance of MyViewController because I don't need it

I'm trying to draw a quarter circle in iOS. In Mac OS, it seems you can use appendBezierPathWithArcWithCenter but this doesn't seem to work in iOS. Does anyone know how to simply draw a quarter circle in iOS? Thanks There are two iOS equivalents, one for UIBezierPath and one for CGPath : UIBezierPath equivalent UIBezierPath *path = [UIBezierPath bezierPath]; [path addArcWithCenter:centerPoint radius:radius startAngle:startAngle endAngle:endAngle clockwise:YES]; CGPath equivalent CGMutablePathRef path = CGPathCreateMutable(); CGPathAddArc(path, NULL, centerPoint.x, centerPoint.y, radius,

I have issue to implement "Emboss/Shadow effects" in my drawing. Finger paint functionality is currently working fine with my custom UIView and below is my drawRect method code: Edit code with all methods : - (void)drawRect:(CGRect)rect { CGPoint mid1 = midPoint(previousPoint1, previousPoint2); CGPoint mid2 = midPoint(currentPoint, previousPoint1); CGContextRef context = UIGraphicsGetCurrentContext(); [self.layer renderInContext:context]; CGContextMoveToPoint(context, mid1.x, mid1.y); CGContextAddQuadCurveToPoint(context, previousPoint1.x, previousPoint1.y, mid2.x, mid2.y); CGContextSetLineCap

I just have a look on CoreImage framework on iOS 5, found that it's easy to add an effect to whole image. I wonder if possible to add an effect on special part of image (a rectangle). for example add gray scale effect on partial of image/ I look forward to your help. Thanks, Huy Felix Watch session 510 from the WWDC 2012 videos. They present a technique how to apply a mask to a CIImage . You need to learn how to chain the filters together. In particular take a look at: CICrop , CILinearGradient , CIRadialGradient (could be used to create the mask) CISourceOverCompositing (put mask images

are there a way for rotate UIImage around external point using CGAffineTranformMAkeRotation? tnx a lot! Here is a function that uses the same format as the CoreGraphics CGAffineTransform API format. This works exactly how other "RotateAt()" APIs should work. The operation represents the equivalent of the following specification: translate(pt.x, pt.y); rotate(angle); translate(-pt.x, -pt.y); CGAffineTransform CGAffineTransformMakeRotationAt(CGFloat angle, CGPoint pt){ const CGFloat fx = pt.x, fy = pt.y, fcos = cos(angle), fsin = sin(angle); return CGAffineTransformMake(fcos, fsin, -fsin, fcos,

I have a table view with custom cells and I try to optimize it by making all subviews inside the cells in green color when Color Blended Layer is checked in the simulator. When the background of an UILabel in the cell is set to white: let title = UILabel() contentView.addSubview(title) title.background = UIColor.whiteColor() title.text = "Hi, how are you?" This UILabel subview will become green color in the simulator, which is good. However, if I change the text to some Chinese: title.text = "你好" The UILabel subview will become red. This SO post provides some explanation about the situation.