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POiOS: capturing CAEmitterLayer particles on screen
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  1. POiOS: capturing CAEmitterLayer particles on screen
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    copied!<p>Is there a way to capture CAEmitterCells (generated using a CAEmitterLayer) when capturing the ios device screen?<br> <strong>UIGetScreenImage()</strong> works, but since it's a private method im not allowed to use it.<br> <strong>UIGraphicsBeginImageContext</strong> doesn't seem to work, the particles are simply omitted from the resulting image.</p> <p><strong>EDIT:</strong> Here is the code I'm currently using to capture the view. I'm actually recording a 30-second-long video of the screen, using the code provided by aroth at <a href="http://codethink.no-ip.org/wordpress/archives/673" rel="noreferrer">here</a>. It works by recording 25 images of itself (its a UIView subclass) and its subviews (in our case including the UIView whose layer is the CAEmitterLayer) per second and uses AVAssetWriter to compose the recording.<br><br> It's quite a mouthful, so I'll just place the relevant lines here: I ARC-ed the code using the ARC tool in XCode, so the code might be a bit different memory management wise.</p> <pre><code>- (CGContextRef) createBitmapContextOfSize:(CGSize) size { CGContextRef context = NULL; CGColorSpaceRef colorSpace; int bitmapByteCount; int bitmapBytesPerRow; bitmapBytesPerRow = (size.width * 4); bitmapByteCount = (bitmapBytesPerRow * size.height); colorSpace = CGColorSpaceCreateDeviceRGB(); if (bitmapData != NULL) { free(bitmapData); } bitmapData = malloc( bitmapByteCount ); if (bitmapData == NULL) { fprintf (stderr, "Memory not allocated!"); return NULL; } context = CGBitmapContextCreate (bitmapData, size.width, size.height, 8, // bits per component bitmapBytesPerRow, colorSpace, kCGImageAlphaNoneSkipFirst); CGContextSetAllowsAntialiasing(context,NO); if (context== NULL) { free (bitmapData); fprintf (stderr, "Context not created!"); return NULL; } CGColorSpaceRelease( colorSpace ); return context; } //static int frameCount = 0; //debugging - (void) drawRect:(CGRect)rect { NSDate* start = [NSDate date]; CGContextRef context = [self createBitmapContextOfSize:self.frame.size]; //not sure why this is necessary...image renders upside-down and mirrored CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, self.frame.size.height); CGContextConcatCTM(context, flipVertical); [self.layer renderInContext:context]; CGImageRef cgImage = CGBitmapContextCreateImage(context); UIImage* background = [UIImage imageWithCGImage: cgImage]; CGImageRelease(cgImage); self.currentScreen = background; //debugging //if (frameCount &lt; 40) { // NSString* filename = [NSString stringWithFormat:@"Documents/frame_%d.png", frameCount]; // NSString* pngPath = [NSHomeDirectory() stringByAppendingPathComponent:filename]; // [UIImagePNGRepresentation(self.currentScreen) writeToFile: pngPath atomically: YES]; // frameCount++; //} //NOTE: to record a scrollview while it is scrolling you need to implement your UIScrollViewDelegate such that it calls // 'setNeedsDisplay' on the ScreenCaptureView. if (_recording) { float millisElapsed = [[NSDate date] timeIntervalSinceDate:startedAt] * 1000.0; [self writeVideoFrameAtTime:CMTimeMake((int)millisElapsed, 1000)]; } float processingSeconds = [[NSDate date] timeIntervalSinceDate:start]; float delayRemaining = (1.0 / self.frameRate) - processingSeconds; CGContextRelease(context); //redraw at the specified framerate [self performSelector:@selector(setNeedsDisplay) withObject:nil afterDelay:delayRemaining &gt; 0.0 ? delayRemaining : 0.01]; } </code></pre> <p>Really hope this helps. Thanks for your support!</p>
 

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