# MCS 260 Project Four due Wed 7 Nov 2007 : randgray.py
#
# A postscript picture with random grayscales.
#
# This program illustrates what we will need to make
# general grayscale pictures.  A grayscale is a number
# between 0 and 255: 0 is black, 255 is white.
# We define a postscript picture by writing grayscales
# for each pixel in hexadecimal notation.

def write_postscript(name,rows,columns):
   """
   Writes to a file with the given name a random picture in
   postscript format, with given number of rows and columns,
   using randomly generated gray scales.
   """
   import random
   XOFFSET = 54
   YOFFSET = 288
   SCALE = 432
   file = open(name + '.ps','w')
   file.write('%!PS\n')
   file.write('%%BoundingBox: 0 300 500 720\n')
   file.write('/picstr %d string def\n' % rows)
   file.write('%d %d translate\n' % (XOFFSET,YOFFSET))
   file.write('%d %d scale\n' % (SCALE,SCALE))
   file.write('%d %d %d\n' % (columns,rows,8))
   file.write('[%d 0 0 -%d 0 %d]\n' % (columns,rows,rows))
   file.write('{currentfile picstr readhexstring pop}\n')
   file.write('image\n')
   for i in range(0,rows):
      for j in range(0,columns):
         n = random.randint(0,255)
         file.write('%.2x' % n)
      file.write('\n')
   file.write('showpage\n')
   file.close()

def main():
   """
   Prompts the user for a file name, the number of rows and
   columns of the postscript file.
   Recommended values for rows and columns are 100.
   """
   print 'generating a random grayscale picture'
   name = raw_input('Give file name : ')
   rows = input('Give #rows : ')
   cols = input('Give #columns : ')
   print 'do ghostview on ' + name + '.ps'
   write_postscript(name,rows,cols)

main()