iOS App Crash when receiving warning memory - iphone

Question

I use two methods to get transparent pixels from UIImage. They are called a lot of times while I drawnig a line in the screen. When the methods start to be called, app crashes, and I get memory warning. I’ve already add #autorelease, and  CGContextFlush(), but it still doesn’t work.How to solve this problem? Anyone knows or have had the same issue?
-(BOOL)isTransparency:(CGPoint)point {
    
    #autoreleasepool {
        
        UIGraphicsBeginImageContext(self.imageView.superview.bounds.size);
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextSaveGState(context);
        CGContextSetBlendMode(context, kCGBlendModeCopy);
        CGContextTranslateCTM(context, [self.imageView center].x, [self.imageView center].y);
        CGContextConcatCTM(context, [self.imageView transform]);
        CGContextTranslateCTM(context,
                              -[self.imageView bounds].size.width * [[self.imageView layer] anchorPoint].x,
                              -[self.imageView bounds].size.height * [[self.imageView layer] anchorPoint].y);
        
        [[self.imageView image] drawInRect:[self.imageView bounds]];
        
        CGContextRestoreGState(context);
        
        CGImageRef image = CGBitmapContextCreateImage(context);
        
        
        CGContextRelease(context);
       
        return [self isTransparentPixel:point image:image];
    }
}
-(BOOL)isTransparentPixel:(CGPoint)point image:(CGImageRef)cgim{
        
        unsigned char pixel[1] = {0};
        
        CGContextRef context = CGBitmapContextCreate(pixel,
                                                     1, 1, 8, 1, NULL,
                                                     kCGImageAlphaOnly);
        CGContextSetBlendMode(context, kCGBlendModeCopy);
        CGContextDrawImage(context, CGRectMake(-point.x,
                                               -(self.imageView.superview.frame.size.height - point.y),
                                               CGImageGetWidth(cgim),
                                               CGImageGetHeight(cgim)),cgim);
        
        CGContextRelease(context);
        
        CGFloat alpha = pixel[0]/255.0;
      
        return alpha < 0.01;
    
    
}

Answer 1

It seems that the image created by CGBitmapContextCreateImage() is not released.
You should release it by CGImageRelease().
By the way, you should not release context retrieved from UIGraphicsGetCurrentContext().
CGImageRef image = CGBitmapContextCreateImage(context);
BOOL isTransparent = [self isTransparentPixel:point image:image];
CGImageRelease(image);
return isTransparent;