Question

I am following a facial recognition app example from Pro iOS 5 Augmented Reality book. I even downloaded the source code… I ran it from there and the problem persists with his code. Here is the problem: It crashes on the assignment of an array that takes the featuresInImage of a CGImage for a CIDetector that is detecting for a face. From logging… it seems that this method is called many many many times… I am using cocos2d_chipmunk so I am using a CSScene. Note that this crash is an EXC_BAD_ACCESS (code=1, address=0x4499923c)
Help please?

  - (void)facialRecognitionRequest:(UIImage *)image {
//NSLog(@"Image is: %f by %f", image.size.width, image.size.height);
if (!isProcessingRequest) {
    isProcessingRequest = YES;
    //NSLog(@"Detecting Faces");
  NSArray* arr = [detector featuresInImage:[CIImage imageWithCGImage:[image CGImage]]]; // CRASHES HERE


    if ([arr count] > 0) {
        //NSLog(@"Faces found.");
        for (int i = 0; i < 1; i++) { //< [arr count]; i++) {
            CIFaceFeature *feature = [arr objectAtIndex:i];
            double xPosition = (feature.leftEyePosition.x + feature.rightEyePosition.x+feature.mouthPosition.x)/(3*image.size.width) ;
            double yPosition = (feature.leftEyePosition.y + feature.rightEyePosition.y+feature.mouthPosition.y)/(3*image.size.height);

            double dist = sqrt(pow((feature.leftEyePosition.x - feature.rightEyePosition.x),2)+pow((feature.leftEyePosition.y - feature.rightEyePosition.y),2))/image.size.width;

            yPosition += dist;
            CGSize size = [[CCDirector sharedDirector] winSize];
            pumpkin.opacity = 255;
            pumpkin.scale = 5*(size.width*dist)/256.0;

            //int randomPumpkin = ((arc4random() % 10) + 5);
            [pumpkin setDisplayFrame:[[CCSpriteFrameCache sharedSpriteFrameCache] spriteFrameByName:[NSString stringWithFormat:@"pumpkin%d.png", pumpkin_count + 4]]];
            CCMoveTo *moveAction = [CCMoveTo actionWithDuration:0 position:ccp((size.width * (xPosition)), (size.height * ((yPosition))))];
            [pumpkin runAction:moveAction];

        }
    } else {
        pumpkin.opacity = 0;

    }    


}
isProcessingRequest = NO;

  }

Assigning the CIDetector:

  - (id)init {
if (self = [super init]) {
  // ....... other stuff here        
    NSDictionary *detectorOptions = [NSDictionary dictionaryWithObjectsAndKeys:CIDetectorAccuracyLow, CIDetectorAccuracy, nil];
    self.detector = [CIDetector detectorOfType:CIDetectorTypeFace context:nil options:detectorOptions]; // CIDetector instance named detector is my property

}
return self;
 }

I tried:
CGImage *theCGImage = [image CGImage];
NSLog(@”theCGImage: %@”, theCGImage);

CIImage *theCIImage = [CIImage imageWithCGImage:theCGImage];
NSLog(@"theCIImage: %@", theCIImage);

NSArray* arr = [detector featuresInImage:theCIImage];
NSLog(@"arr: %@", arr);

Here are the results:

 2012-04-15 19:08:25.136 Ch8[981:609f] tmpCGImage: <CGImage 0x1f689c00>
 2012-04-15 19:08:25.143 Ch8[981:609f] tmpCIImage: <CIImage: 0x1f687970 extent [0 0 480 360]>
 2012-04-15 19:08:25.282 Ch8[981:609f] arr: (
"<CIFaceFeatureInternal: 0x1f58e080>"
)

I also tried enabling NSZombies but still no luck… any ideas?

Answer 1

In answer to the comment (not the entire question, presented as answer just for the formatting):
“how would i do that do i just write if statements to see if they are non-zero then log it?”

Instead of:

  NSArray* arr = [detector featuresInImage:[CIImage imageWithCGImage:[image CGImage]]];

break it up into three statements:

CGImage *theCGImage = [image CGImage];
NSLog(@"theCGImage: %@", theCGImage);

CIImage *theCIImage = [CIImage imageWithCGImage:theCGImage];
NSLog(@"theCIImage: %@", theCIImage);

NSArray* arr = [detector featuresInImage:theCIImage];
NSLog(@"arr: %@", arr);

So that the offending statement can be found. This is a general debugging technique and not a bad way to write the code in any case.

The NSLog statements are not really necessary, a breakpoint on the first statement and then single step through.

For crashes due to premature releases use NSZombies. It can be enabled in Xcode under “Edit Scheme, tab: “Diagnostics”, be sure to turn it off when running on the device.