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Questions tagged [cgcontextref]

90 questions
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CGContextRef inset?

So, I have this code, that draws a circle with a line around it. - (void)drawRect:(CGRect)rect { CGContextRef contextRef = UIGraphicsGetCurrentContext(); CGContextSetLineWidth(contextRef, 40.0); CGContextSetRGBFillColor(contextRef, 0.0,…
Sjakelien
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Invalid context warnings with CGContextSetFillColorWithColor

I'm writing an app for the iPad and on iOS 7 I get a littany of warnings in the console along the line of: : CGContextSetFillColorWithColor: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an…
easythrees
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iOS7 screenshot not taking into consideration blur effect

I'm taking screen shot with this code - (UIImage *)screenshot { UIGraphicsBeginImageContext(self.bounds.size); [self.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); …
Avba
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CGContextFillPath(context) gets removed when creating a line

I use the below code for fill path in viewDidLoadit works perfect UIGraphicsBeginImageContext(_drawingPad.frame.size); CGContextRef context1 = UIGraphicsGetCurrentContext(); CGContextMoveToPoint(context1, 300,…
Karthikeyan T
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Invalid context in drawRect

I'm trying to draw some bezier paths in my view's drawRect method, but I keep getting an invalid context error. I don't understand why, because I thought that there was always a context when drawRect is called. Am I missing something? This is the…
LunaEques
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CGContextRef gives Error

i am using CGContextRef to draw one horizontal bar and above-below of bar i am displaying text using drawInRect method of NSString.Here is code: CGContextRef context = UIGraphicsGetCurrentContext();//set frame for bar CGRect frame; …
user2470111
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Incompatible pointer types initializing 'CGContextRef *'

Not gonna lie, I'm trying to follow a tutorial in a book and I can't get past this warning. Incompatible pointer types initializing 'CGContextRef *' (aka 'struct CGContext **') with an expression of type 'CGContextRef' (aka 'struct CGContext *') The…
nipponese
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UIImage remove some pixels issue

I have the application where user can erase image. So if user touches some px of the image, alfa of these pixels should become lower. For instance, if I touched (0,0) pixel of the image one time, (0,0) px opacity should become 0.9. If I touched that…
Paul T.
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Drawing a line between the coordinates in MKMapView

I want to draw the lines between the coordinates in MKMapView..Here is the code aRoute=[NSArray arrayWithObjects:[[CLLocation alloc] initWithLatitude:40.445418 longitude:-79.942714],[[CLLocation alloc] initWithLatitude:40.444469…
Icoder
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iOS the lower performance of CGContext when draw a lot of gradient rectange

The effect I want to implement: Here is the code snippet: for (NSInteger i = 0; i < count; i++) { key = [NSString stringWithFormat:@"Property%d", i]; barHeigth = valueHeight * ([[_values objectAtIndex:i] floatValue]/valueMax); …
HeavenSword
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iPhone - draw a transparent (cleared) rectangle with customized border

I'm trying to draw a rectangle, which should have black color border of width 5.0, I am getting the rectangle as seen below, CGContextRef context = UIGraphicsGetCurrentContext(); CGContextStrokePath(context); CGContextSetRGBFillColor(context, 0.0,…
Hemang
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Draw 16 dots in Circular path with CGContextRef

How can I add 16 dot in circular path when the user select a location x,y in my View and the dots should be in a equal distances, so when the user hit a location in the view, I will complete the circle with 16 dot, see attachment. the image is the…
Aziz
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CGBitmapContextCreate bitsPerComponent for RBG565

I'm trying to create a CGContextRef using CGBitmapContextCreate. The bitmap I want to create is RBG565 (red and blue are 5 bits, green is 6 bits). One of the parameters for CGBitmapContextCreate is bitsPerComponent. Since I have variable…
yeesterbunny
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Misunderstanding with CALayer in CGContextRef

I have a custom view in which I want to display a CALayer with PDF content. To do so I implemented a delegate NSObject subclass as shown in the first answer to Using CALayer Delegate. Since I have a document-based app, I have a starting window…
BigCola
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Getting the CGContextRef from a subview

I'm using UIGraphicsGetCurrentContext() to create a gradient background for a UI element, but I guess I misunderstood where the drawing was taking place. I wanted the drawing to take place on a subview, but instead it's happening in the view itself.…
Andrew
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