How do I determine when the "bug" has reached the end of the picture? JES Programming

The psudeo code I am following is:

• Have the user pick a picture from a file, and show it. Get its width (w) and height (h).
• Assign variables x and y to the center of the picture.
• Let pixelsEaten be the number of pixels the bug has eaten; initially set it to 0.
• Let hungerLevel count the number of consecutive steps the bug has eaten nothing; initially set it to 0.

Repeat the following until hungerLevel reaches 400:

• Get the pixel at position (x,y) in the picture If the color is white
• The bug has encountered a blank spot!
• add 1 to hungerLevel

else

• The bug is back on the tapestry and “eats” the pixel !
• set the pixel to white add 1 to pixelsEaten
• set hungerLevel back to zero Repaint the picture

The bug moves (up to) one pixel horizontally: add a random number (-1,0,or1) to x

The bug moves (up to) one pixel vertically: add a random number (-1,0,or1) to y

If x goes off the picture to the left, reset it to 0

If x goes off the picture to the right, reset it to w-1

Do a similar thing for y if it goes off the top or bottom

In an information box display a message showing the percentage of the tapestry that the bug ate.

I have completed everything except for the pseudo code in bold. How do I determine when the "bug" moves off the picture to the left and right / up and down?

My code so far is below:

  from random import*
  from time import*
def main():
  showInformation(" Pick a graphics file, preferably one showing a tapestry " ) 
  file= pickAFile()
  pic= makePicture( file ) 
  show( pic ) 
  w= getWidth( pic ) 
  h= getHeight( pic ) 
  x= w/2
  y= h/2
  pixelsEaten= 0 
  hungerLevel= 0 




  while hungerLevel != 400:
    px= getPixelAt( pic, x, y ) 
    x= x + randrange( -1, 2 ) 
    y= y + randrange( -1, 2 ) 

   if px == white:
     hungerLevel= hungerLevel + 1


   else:
     setColor( px, white ) 
     pixelsEaten= pixelsEaten + 1
     hungerLevel= 0
     repaint( pic )