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    <p><img src="https://i.stack.imgur.com/4zqWd.png" alt="Dot Image"></p> <p>The key to the approach used to draw the image shown above is using <code>CGContextDrawRadialGradient</code> to draw the dot. We can then use this dot image as the contents of a <a href="https://developer.apple.com/library/ios/#documentation/graphicsimaging/reference/CALayer_class/Introduction/Introduction.html" rel="nofollow noreferrer">CALayer</a>, allowing us to reposition it and animate it as we see fit. </p> <p>In your original question you asked...</p> <blockquote> <p>how to make that center point with <strong>animation effect</strong> shown in Image?</p> </blockquote> <p>...but as a still image it doesn't show any animation. I've made an educated guess as to how you envisioned the dot be animated.</p> <p>The following code creates a gradated dot with a pulsating animation, fading in and out repeatedly:</p> <h2>Code</h2> <pre><code>#import &lt;QuartzCore/QuartzCore.h&gt; ... - (void)viewDidLoad { [super viewDidLoad]; CGFloat dotDiameter = 30.f; CGFloat dotRadius = dotDiameter * 0.5; CGRect dotRect = CGRectMake(CGRectGetMidX(self.view.frame) - dotRadius, CGRectGetMidY(self.view.frame) - dotRadius, dotDiameter, dotDiameter); CALayer *dotLayer = [CALayer layer]; dotLayer.contents = (id)[self dotImageOfDiameter:dotDiameter].CGImage; dotLayer.cornerRadius = dotRadius; dotLayer.frame = dotRect; dotLayer.masksToBounds = YES; // Animate the dot to make it appear to pulsate. CABasicAnimation *pulseAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"]; pulseAnimation.autoreverses = YES; pulseAnimation.duration = 0.8; pulseAnimation.fromValue = [NSNumber numberWithFloat:0.0f]; pulseAnimation.repeatCount = INFINITY; pulseAnimation.toValue = [NSNumber numberWithFloat:1.0f]; [dotLayer addAnimation:pulseAnimation forKey:@"opacity"]; [self.view.layer addSublayer:dotLayer]; } - (UIImage *)dotImageOfDiameter:(CGFloat)diameter { UIGraphicsBeginImageContextWithOptions(CGSizeMake(diameter, diameter), NO, 0.0f); CGContextRef context = UIGraphicsGetCurrentContext(); CGFloat radius = diameter * 0.5; CGColorSpaceRef baseColorSpace = CGColorSpaceCreateDeviceRGB(); CGFloat colours[8] = { 0.56f, 0.78f, 0.94f, 1.0f, // Opaque dot colour. 0.56f, 0.78f, 0.94f, 0.0f }; // Transparent dot colour. CGGradientRef gradient = CGGradientCreateWithColorComponents (baseColorSpace, colours, NULL, 2); CGContextDrawRadialGradient(context, gradient, CGPointMake(radius, radius), 0.0f, CGPointMake(radius, radius), radius, kCGGradientDrawsAfterEndLocation); CGImageRef dotImageRef = CGBitmapContextCreateImage(context); UIImage *dotImage = [UIImage imageWithCGImage:dotImageRef]; CGColorSpaceRelease(baseColorSpace); CGGradientRelease(gradient); CGImageRelease(dotImageRef); UIGraphicsEndImageContext(); return dotImage; } </code></pre>
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