core-graphics

We're creating an iOS photo app. In doing this, we have to create dynamically sized images up to about 2500x1600px. Once this image has been created, we want to draw smaller images on top of the big one reasonably quickly. The problem as we can see it is that it's impossible to get a context larger than the screen resolution. The call does not crash, but it returns a nil-context. How can such a seemingly simple task be achieved? Secondly, once this context is created, what is the fastest way to draw a small image at a given position on top of the big one? Edit: We found the solution.

I'm trying to draw a single, straight line using core graphics and swift 3 However, when touchesmoved is called, it creates multiple lines instead of just a single line. Code used is below: import UIKit class ViewController: UIViewController { @IBOutlet weak var drawingPlace: UIImageView! var startTouch : CGPoint? var secondTouch : CGPoint? override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { let touch = touches.first startTouch = touch?.location(in: drawingPlace) } override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) { for touch in touches{

I'm working on a multithreaded OpenGL compositing engine. I have a set of shaders which I'm sharing among multiple contexts. For performance reasons, I'd like to avoid compiling a separate instance of each shader program for each thread. But, if multiple threads happen to use the same program object and I try to set different uniforms on each thread, the uniform values get mixed up since uniform values are stored with the shared program object. So far I see my options as: compile a separate program object for each thread (which wastes time and resources), or for each shared program object,

I am trying to modify the PDF metadata (title, author, etc.) of an existing PDF on iOS. While it is easy to find sample code for PDF parsing and for PDF creation from scratch, there does not seem to be an easy way to dump an existing PDF into a new file - and modify it just slightly. More specifically, how do I get the info obtained when reading a PDF roughly like this: CGPDFDocumentRef myPDF = CGPDFDocumentCreateWithURL((CFURLRef)urlOfInputPDF); CGPDFDictionaryRef myPDFDict=CGPDFDocumentGetInfo(myPDF); into the new PDF, which I would create roughly this way: CGRect pageRect;

I have a image in rectangle shape but i want to crop this image in a star shape in my iphone application. so please can any one suggest how i do this? plz suggest. thanks DarkDust See the comment to a related question on how to mask an image. The magical part is CGContextClipToMask . 来源： https://stackoverflow.com/questions/5701152/crop-image-in-star-shape-iphone

I've written a program for drawing in iOS in touchesMoved() method. CGContextAddPath(UIGraphicsGetCurrentContext(), path); CGPathMoveToPoint(path, NULL, lastPoint.x, lastPoint.y); CGPathAddLineToPoint(path, NULL, lastPoint.x, lastPoint.y); CGContextDrawPath(UIGraphicsGetCurrentContext(), kCGPathStroke); How can i clear the path drawn and restore the original view? Perhaps you can put an invisible view above your view of drawing and add the path traced by the user only when u are sure that the user will not undo. If the user wants the undo action, don't add the path to the context. Thats my