gistfile1.m

static void clipApplier(void *info, const CGPathElement *element)
{
    NSMutableArray *a = (NSMutableArray*)info;
    
    int nPoints;
    switch (element->type)
    {
        case kCGPathElementMoveToPoint:
            nPoints = 1;
            break;
        case kCGPathElementAddLineToPoint:
            nPoints = 1;
            break;
        case kCGPathElementAddQuadCurveToPoint:
            nPoints = 2;
            break;
        case kCGPathElementAddCurveToPoint:
            nPoints = 3;
            break;
        case kCGPathElementCloseSubpath:
            nPoints = 0;
            break;
        default:
            [a replaceObjectAtIndex:0 withObject:[NSNumber numberWithBool:NO]];
            return;
    }
    
    if (nPoints > 0) 
    {
        CGPoint *p = element->points;    
        for (int i = 0; i < nPoints; i++) 
        { 
            if (p->x > 320 || p->x < 0 || p->y < 0 || p->y > 460) 
                return;  
            p++;     
        }    
    }
    
    NSNumber *type = [NSNumber numberWithInt:element->type];
    NSData *points = [NSData dataWithBytes:element->points length:nPoints*sizeof(CGPoint)];
    [a addObject:[NSDictionary dictionaryWithObjectsAndKeys:type,@"type",points,@"points",nil]];
}