Applying the following code to convert from a grayscale image to threshold but the output would be a total black picture any ideas:

PImage toThreshhold(PImage sourcePic) 

{ 

      PImage thresh = new PImage(sourcePic.width,sourcePic.height); 

sourcePic.loadPixels(); 

for(int i = 0; i < sourcePic.width; i++) 

{ 

      for(int j = 0; j<sourcePic.height; j++)

{

 int pixPosition = i*sourcePic.width +j;

 if(sourcePic.pixels[pixPosition] > 127) {

 sourcePic.pixels[pixPosition] = color(255); 

} 

else { 

sourcePic.pixels[pixPosition] = color(0); 

      }

    }

 } 

sourcePic.updatePixels();

 return thresh; 

}