Computer Science 101
                                   Program 2
                               Due Oct 30 at 11:59 pm

Write a complete C program named gray.c that will BOTH convert a color RGB
image (P6) to a grayscale image (P5) AND resize it to new dimensions that
are specified on the command line.

   For this program the ONLY authorized source of assistance is
   Dr. Westall. ANY OTHER DISCUSSION of the program no matter how "high
   level" or "peripheral" (e.g. Have you started/finished it yet?)
   is STRICTLY FORBIDDEN.  Any student who observes improper behavior
   is encouraged to report it to Dr. Westall. Reports that can be
   verified will be rewarded with a 20 point bonus on the assignment for
   the student doing the reporting and an F for the course for the
   student being reported!!

For converting RGB pixels to grayscale use the following conversion
algorithm

           gray = 0.3 Red + 0.5 Green + 0.2 Blue

For example, suppose the values of the three bytes of an input pixel are

           Red = 240  Green = 128 Blue = 200

Then the gray pixel should have the value:

           72 + 64 + 40 =  176

Be REAL SURE that you declare your pixel values as "unsigned char".

Program operation:

As usual your program will read the input image from stdin and
write the output image to stdout. It will be invoked with a
command line similar to the following:

   a.out  800 200 < input.ppm  > output.ppm


The basic algorithm should be as follows:

- acquire output dimensions from the command line parameters
  and assign them to variables outcols and outrows
- read ppm header of input image and assign dimensions to variables
  incols and inrows
- malloc space for reading in the input image data (3 * inrows * incols)
- malloc space for building the output image (outrows * outcols)
- use  a single call to fread to read the input image pixel data
- for each row of the output image
     for each column of the output image
         compute the (row, col) of corresponding pixel in input image
         use the (r,g,b) components of the corresponding pixel in the
             input image to compute the gray level of the output pixel
         store the output pixel in the output image buffer.
- Write the P5 .ppm header for the output image
- Use a single call to fwrite to write the output image.

----------------------------------------------------------
Computing the location of the "corresponding pixel" must be done as
follows. The discussion is column based but row computations
are analogous.

Suppose the output image has 914 columns, the input image has 644
columns, and we seek to find the corresponding column for
output image column 833.

-   Since 833 / 914 = 0.9114 the output pixel is
    at a distance 91.14% of the width from the left edge.

-   Thus the corresponding column in the input image is 0.9114
    0.9144 * 644 = 586.93 = 586

Notes: You must use floating point to compute the fractional
amount. You must convert back to integer to obtain the final
column. You should not try to round to the nearest integer lest
you compute column 644.

   Adhere to the following programming standards.  Violations will
   lead to deductions.

   (1) no function should be longer than 30 lines code + whitespace.
   (2) the maximum nesting level in any function is ONE
   (3) code lines should not extend beyond column 72
   (4) no more that one statement may be written on a single line
   (5) use reasonably descriptive names for variables and functions
   (6) package all functions into a single source code module named gray.c
   (7) your program should compile without any warnings with gcc -Wall
   (8) indenting should be consistent with logical nesting
   (9) diagnostic / debug prints should be disabled/deleted in
       your submission.