PPM Files

Objectives

1. Write a program that can produce gif or jpeg files.
2. Write a program that can produce ppm files.

Notes

• PPM is an easy form of graphics file
  • The PPM format is described here.
  • PPM is useful as the format is easily written by a programmer without libraries or special knowleged.
  • Then there are a library of converters
  • I selected jpeg for my final form.
• I will use the system command
  • This takes a string and executes it in a subshell
  • A poor man's fork.
• I will also call unlink
  • Remember, this removes a file.
• Do the following:
  1. Download lab1.cpp
     • wget https://mirkwood.cs.edinboro.edu/~bennett/class/cmac3580/spring2025/notes/parallel/code/lab1/lab1.cpp
  2. Look the code over, any questions?
  3. Add a (possibly triple nested loop) to initialize the image
  4. We will want to write raw data, and we know how to do that with write, so open the file pngName for writing
     • truncate or create
     • Make it readable by everyone, we will eventually want to put this in a web directory so we can view the images.
  5. Write the file header
     • This is all ascii
     • A magic number (P6) followed by an endl
     • The size: width height and an endl( assume 1000 400)
     • The maximum intensity and a newline (assume 255)

     • P6
       1000 400
       255
                     

  6. Write the data, row by row,
• If you need it, you can download my final product:
  • wget https://mirkwood.cs.edinboro.edu/~bennett/class/cmac3580/spring2025/notes/parallel/code/lab1/finalProduct.cpp