Math 144 - Partial Differential Equations Image Processing Project

*** Objective ***

The purpose of this README is to explain the .ppm image format, how to use the
included image C++ class, where the students should do their PDE programming,
how to compile the program, how to use user-interface, and how to debug
errors.

*** The Portable Pixmap Image (.ppm) Format ***

For simplicity, the image processing project uses the portable pixmap image
(.ppm) format.  In reality, this format is rarely used.  One reason is its
lack of compression, making it inefficient compared to other image formats. 
However, it is great for learning, since reading and writing them is simple. 
To view .ppm images, a third-party image viewer may be needed (such as
LViewPro for the Windows operating system).

*** The ``image'' C++ Class ***

To aid the student, the ``image'' C++ class has been created to take care of
all reading and writing of .ppm images.  It also takes care of dynamic memory
allocation, and provides many useful functions.  To view the available
functions and how to use them, please see the file ``ppm.h''.

For details about how the ``image'' C++ class works, please see the file,
``ppm.cpp''.  Note that this level of detail is NOT necessary to complete the
project successfully.

*** Where to Program ***

The student only needs to modify the file, ``pde.cpp''.  There are many
comments in it, explaining where to program.  The heat equation has been
included as an example for the student.  However, it depends on some macros
(the ``#define'' statements at the top of ``pde.cpp'') that the student must
write.

*** Compiling the Program ***

For students using Dev-C++, a free Windows C++ compiler, add the files to a
new project.  For help with this, see the "Dev-C++ and Projects" link located
below the link you clicked to get to this README file.

For students using g++ in a Unix-based environment, a ``Makefile'' has been
included.  Simply type ``make'' at the command prompt to compile the program.

*** Running the Program ***

A user-interface has been included in ``imagepro.cpp''.  Note it is NOT
necessary to understand this file to complete the project successfully. When
the program is run, the user-interface prompts the student with which image to
use, which equation to apply, and other parameters.  This will call the
student's PDE functions, which were implemented in ``pde.cpp''.

For more advanced students, command line arguments may be used instead of the
user interface.  The usage format is: <executable> [FILENAME PDE delta_t]

In Windows environments, such as Dev-C++, the program window may immediately
close when the program is finished.  To prevent this, run the executable from
the command prompt.  Or, for advanced users, add a getch() function call
before return and exit statements.

*** Debugging ***

When the program does not behave as expected, there may be an error in the
program.  Included in the ``image'' class is a function that saves each pixel
of an image as a comma-delimited file (.csv).  The function is called
save_csv(), and how to use it is explained in ``ppm.h'' (along with how to use
every other ``image'' function).  In the comma-delimited file, each value will
be separated by commas and is viewable by any text editor.  However, it is
recommended that the student use a spreadsheet program, such as Microsoft
Excel, to view the file.

The file ``imagepro.cpp'' has two lines of code near the bottom that call
save_csv().  These are commented-out.  To save a comma-delimited file after
the PDE calls, uncomment these lines so that they can run.