core-graphics

问题 Im' trying to replace all pixels of input image with closest available RGB. I have a array contain color and input image. Here is my code, it give me an output image as expected, BUT it take very LONG time( about a min) to process one image. Can anybody help me improve the code? Or if you have any other suggestions, please help. UIGraphicsBeginImageContextWithOptions(CGSizeMake(CGImageGetWidth(sourceImage),CGImageGetHeight(sourceImage)), NO, 0.0f); //Context size I keep as same as original

问题 I've been struggling with this for a couple of hours, and I'm hoping someone else has some insight. I'm looking for a way to get the average RGB color of a 1x1 UIImage. So far I've created a CGImageRef from the UIImage, but I'm really new to CoreGraphics, so I'm not sure where to go from there. Any help is appreciated. Thanks! 回答1: If you have a CGImage, you get the data by calling CGDataProviderRef CGImageGetDataProvider ( CGImageRef image ); CGImage doc Then you can copy the data CFDataRef

问题 Question How to use these private functions on other windows? It would be nice to have this knowledge back in the wild. I am specifically trying to get CGSOrderWindow and CGSSetWindowLevel to work. I was trying in the direction of: temporarily register as the dock and then register the dock as the dock again immediately afterwards or code injection into the Dock process per this comment: Also, the author of the above project seems determined to make all core functionality available as a

问题 When I perform the following only on the main thread iref gets autoreleased immediately: -(void)loadImage:(ALAsset*)asset{ @autoreleasepool { ALAssetRepresentation* rep = [asset defaultRepresentation]; CGImageRef iref = [rep fullScreenImage]; UIImage* image = [UIImage imageWithCGImage:iref scale:[rep scale] orientation:UIImageOrientationUp]; [self.imageView setImage:image]; } } But when I perform imageWithCGImage: with GCD on a background thread iref does not get released instantly like in

问题 I am new to iPhone development. I used [NSTimer scheduledTimerWithTimeInterval:0.01] for game loop. The game consists drawscreen function in which I use CGContextClipToRect to clip the large images for animation. But the speed 0.01 seconds is working in simulator only not on device. How can I overcome this problem? The timer code is in view controller as (void)viewDidLoad { GameView *main = [[GameView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; main.backgroundColor =

问题 I try to add a CAGradient effect in a pie chart I make with Core Graphics. It turns out I am not able and certainly not understand very well how to apply it to a view that is part of a CGPath... override func draw(_ rect: CGRect) { ... func arc(myRadius: CGFloat, myStartAngle: CGFloat, myEndAngle: CGFloat) { // This is the pie chart segment context?.setFillColor(phenotypeColor.cgColor) context?.move(to: center) context?.addArc(center: center, radius: finalRadius, startAngle: myStartAngle,

问题 I need to resize more image in one "for" but if I use UIGraphicsGetImageFromCurrentImageContext, I don't have enough memory for more images, because it stay on autorelease and images released when "for" is terminated. I need another method for resize. Any ideas. Thanks -(UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize { CGSize targetSize = newSize; CGSize imageSize = image.size; CGFloat width = imageSize.width; CGFloat height = imageSize.height; CGFloat targetWidth =

问题 When I call setNeedsDisplay() on my UIView's CALayer (either directly, or via needsDisplayOnBoundsChange ), it draws the background as black. myView.layer.setNeedsDisplay() When I call 'setNeedsDisplay()' on the UIView directly, it doesn't show up as black: myView.setNeedsDisplay() Why does this happen, and how can I fix it? 回答1: The problem was that my view's background color was somehow set to nil instead of .white or .clear , for example. It seems odd that this happens only when calling it

问题 I'm looking for the fastest way to draw offscreen CALayer content (no alpha needed) on macOS. Note, that these examples aren't threaded, but the point is (and why I'm not just using CALayer.setNeedsDisplay) because I'm doing this drawing on a background thread. My original code did this: let bounds = layer.bounds.size let contents = NSImage(size: size) contents.lockFocusFlipped(true) let context = NSGraphicsContext.current()!.cgContext layer.draw(in: context) contents.unlockFocus() layer

问题 This question already has answers here : Assigning an existing CGColor to a CGColor property works in iOS Simulator, not iOS device. Why? (3 answers) Closed 6 years ago . I am subclassing UIView and using instances of that to set my UITableViewCell backgroundView and selectedBackedView properties. I am receiving an EXC_BAD_ACCESS error in the drawRect method of my UIView subclass. if(nil == cell){ cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier