Question

I have implemented a recursive function on image which call its neighbor pixels until conditions get finalized, I have been able to run this code successfully upto 200×200 image resolution but when image size increases then it will get crashed with EXC_BAD_ACCESS error at the following stack line ___lldb_unnamed_function782$$libicucore.A.dylib. I have checked mine code and not able to detect any error, might be it is due to too many recursive call back functions. If anyone has any idea then please let me know.

This is mine recursive code :

 -(void)magicImageContext:(unsigned char*)data point:(CGPoint)point red:(unsigned char)red green:(unsigned char)green blue:(unsigned char)blue bytesPerPixel:(NSInteger)bytesPerPixel bytesPerRow:(NSInteger)bytesPerRow size:(long long int)size width:(NSInteger)width height:(NSInteger)height maskedData:(unsigned char*)masked_data{
for(int x = point.x-1; x<=point.x+1; x++){
    for(int y = point.y-1; y<=point.y+1; y++){
        if((x == point.x) && (y == point.y)) {
        }
        else if((x<0) || (y<0) || (x>=width) || (y>=height)){
        }
        else if([self checkPixelMarkedAtPoint:CGPointMake(x, y) data:masked_data]){
            int byteIndex = (bytesPerRow * y) + x* bytesPerPixel;
            CGFloat red2   = (data[byteIndex] );
            CGFloat green2 = (data[byteIndex + 1]);
            CGFloat blue2  = (data[byteIndex + 2]);
            if([self checkColorThresholdWithRed1:red green1:green blue1:blue red2:red2 green2:green2 blue2:blue2]){
                NSLog(@"x= %d, y= %d %d",x,y,byteIndex);
                //mark pixels on masked image
                [self changemaskedData:CGPointMake(x,y) data:masked_data];
                [self magicImageContext:data point:CGPointMake(x, y) red:red green:green blue:blue bytesPerPixel:bytesPerPixel bytesPerRow:bytesPerRow size:size width:width height:height maskedData:masked_data];                }
        }
    }
}
}

Answer 1

If you’re using recursion across all the pixels of an image, then inputting a large image will certainly result in a stack overflow.

Consider rewriting your function to use an explicit stack and a loop to avoid recursion. This also may improve the performance of your app as it avoids relatively-expensive function calls.