Processing Images on a background thread, and wrapping them up in NSOperations ... just to be pretty

FRImageOperation.m

#import <Foundation/Foundation.h>
#import <QuartzCore/QuartzCore.h>

@interface FRImageOperation : NSOperation {

}

@end


@implementation FRImageOperation

- (id)init{
	if( (self = [super init]) ){
	    //Do some custom initialization 
	}
	
	return self;
}
	   
- (void)dealloc {
    
    [super dealloc];
}

- (void) main{
	
	NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
	//////////////////////////////////////////

	UIImage				*backgroundImg;
	CGLayerRef			layer;
	
	CGImageRef			resultImage;
	
	CGContextRef		context, layerContext;
	void				*bitmapData;
	CGColorSpaceRef		colorSpace;
	CGSize				canvasSize;

	int					bitmapByteCount;
	int					bitmapBytesPerRow;
	
	//Get the background image
	backgroundImg = [UIImage imageNamed:@"sample.jpg"];
	
	//Initialize the canvas size!
	canvasSize = [backgroundImg size];
	
	//
	bitmapBytesPerRow	= (canvasSize.width * 4);
	bitmapByteCount		= (bitmapBytesPerRow * canvasSize.height);
	
	//Create the color space
	colorSpace = CGColorSpaceCreateDeviceRGB();
	
	bitmapData = malloc( bitmapByteCount );
	
	//Check the the buffer is alloc'd
	if( bitmapData == NULL ){
		DebugLog(@"Buffer could not be alloc'd");
	}
	
	//Create the context
	context = CGBitmapContextCreate(bitmapData, canvasSize.width, canvasSize.height, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast);
	
	if( context == NULL ){
		DebugLog(@"Context could not be created");
	}
	
	layer = CGLayerCreateWithContext(context, canvasSize, NULL);
	
	if( layer == NULL ){
		DebugLog(@"Layer could not be created");
	}
	
	layerContext = CGLayerGetContext(layer);
	
	if( layerContext == NULL){
		DebugLog(@"No Layer context");
	}
	
	
	//Draw the image into the bitmap context
	CGContextDrawImage(context, CGRectMake(0.0f,0.0f,backgroundImg.size.width,backgroundImg.size.height), [backgroundImg CGImage]);
	
        //Fill color set to green
	CGContextSetRGBFillColor(layerContext,0.33f,0.66f,0.33f,1.0f );
	
	//Draw a green square
	CGContextFillRect(layerContext, CGRectMake(0.0f,0.0f,200.0f,200.0f));
	
	//Draw the layer in the context
	CGContextDrawLayerAtPoint( context, CGPointMake(0.0f, 0.0f), layer);
	
	//Get the result image
	resultImage = CGBitmapContextCreateImage(context);
	
	//Save the image to the photos album
	UIImageWriteToSavedPhotosAlbum( [UIImage imageWithCGImage:resultImage],self,@selector(image:error:context:),NULL);
	
	//Cleanup
	free(bitmapData);
	CGColorSpaceRelease(colorSpace);
	CGImageRelease(resultImage);
	
	DebugLog(@"Complete Processing");
	
	//////////////////////////////////////////
	[pool drain];
	
}

-(void) image:(UIImage*) aImage error:(NSError*) aError context:(void *) aContext{
	DebugLog(@"Completed saving");
}

@end