core-graphics

I need to draw centered text to a CGContext. I started with a Cocoa approach. I created a NSCell with the text and tried to draw it thus: NSGraphicsContext* newCtx = [NSGraphicsContext graphicsContextWithGraphicsPort:bitmapContext flipped:true]; [NSGraphicsContext saveGraphicsState]; [NSGraphicsContext setCurrentContext:newCtx]; [pCell setFont:font]; [pCell drawWithFrame:rect inView:nil]; [NSGraphicsContext restoreGraphicsState]; But the CGBitmapContext doesn't seem to have the text rendered on it. Possibly because I have to pass nil for the inView: parameter. So I tried switching text

I'm looking for help with a performance issue in an Objective-C based iOS app. I have an iOS application that captures the screen's contents using CALayer's renderInContext method. It attempts to capture enough screen frames to create a video using AVFoundation. The screen recording is then combined with other elements for research purposes on usability. While the screen is being captured, the app may also be displaying the contents of a UIWebView, going out over the network to fetch data, etc... The content of the Web view is not under my control - it is arbitrary content from the Web. This

I am using the framework of route-me for working with locations. In this code the path between two markers(points) will be drawn as a line. My Question: "What code should I add if I want to add an arrow in the middle(or top) of the line, so that it points the direction" Thanks - (void)drawInContext:(CGContextRef)theContext { renderedScale = [contents metersPerPixel]; float scale = 1.0f / [contents metersPerPixel]; float scaledLineWidth = lineWidth; if(!scaleLineWidth) { scaledLineWidth *= renderedScale; } //NSLog(@"line width = %f, content scale = %f", scaledLineWidth, renderedScale);

I'm trying to build an eraser tool using Core Graphics, and I'm finding it incredibly difficult to make a performant eraser - it all comes down to: CGContextSetBlendMode(context, kCGBlendModeClear) If you google around for how to "erase" with Core Graphics, almost every answer comes back with that snippet. The problem is it only (apparently) works in a bitmap context. If you're trying to implement interactive erasing, I don't see how kCGBlendModeClear helps you - as far as I can tell, you're more or less locked into erasing on and off-screen UIImage / CGImage and drawing that image in the

I have this app with a full screen tableView that displays a bunch of tiny images. Those images are pulled from the web, processed on a background thread, and then saved to disk using something like: dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ UIGraphicsBeginImageContextWithOptions(rect.size, YES, 0); // code that adds some glosses, shadows, etc UIImage *output = UIGraphicsGetImageFromCurrentImageContext(); NSData* cacheData = UIImagePNGRepresentation(output); [cacheData writeToFile:thumbPath atomically:YES]; dispatch_async(dispatch_get_main_queue(), ^{

I have an UIImage and want to shift it's saturation about +10%. Are there standard methods or functions that can be used for this? There's a CoreImage filter for this. CIColorControls Just set the inputSaturation to < 1.0 to desaturate or > 1.0 to increase saturation... eg. Here's a method I've added in a category on UIImage to desaturate an image. -(UIImage*) imageDesaturated { CIContext *context = [CIContext contextWithOptions:nil]; CIImage *ciimage = [CIImage imageWithCGImage:self.CGImage]; CIFilter *filter = [CIFilter filterWithName:@"CIColorControls"]; [filter setValue:ciimage forKey

I want to render some text on one of my screens that has a 3dish look to it. I am using UIKit and standard views controllers etc. The effect will look something like this: Can this be done somehow with UIKit & iOS? Ordinarily I would just use a static png however, the text is dynamic and updates based on user data The following code might not be perfect, but it should be a good starting point. Basically you draw the font twice, slightly changing the size and the offset. Depending on the font and size you're dealing with you're probably have to play a bit with fontSize , fontSizeDelta and