The purpose of this project is to make a collection of images in the style of Andy Warhol. You'll do this by manipulating the pixel colors of an image.

Tasks

Make sure you have copies of the graphics.py and display.py files.

For this assignment you're going to create two python programs. One will generate a Warhol style collage. The other will change the blue screen to a different color. Both will write their results to an image file, which you can then view with your show program.

In your filter.py file, create a function putPixmap which takes four arguments. The first argument will be a destination Pixmap, the second argument will be a source Pixmap, and the last two arguments will be an x, y location to place the second Pixmap into the first. The function outline in comments is given below.
For each comment inside the function below, you need to write one line of python code.
```
# place source into destination upper left at x, y in destination
def putPixmap( destination, source, x, y ):
    # loop over each row, i, in source
        # loop over each column, j, in source
            # from source, get the (r, g, b) value at pixel (j, i)
            # in destination, set location (x + j, y + i) to (r, g, b)
```
Once you have written your function, you can use this file to test it. Run the test program on the command line and give it an image filename as its argument. For example:

python testPutPixmap.py miller.ppm

Remember that the Zelle graphics package can read only PPM type images.

Once you are confident about the code, remove the comments that we supplied. Because they simply describe each line of code, they don't help the reader understand the overall purpose of the code. Helpful comments include the docstring (which you need to write), which explains the meaning of each parameter. If you find them helpful because they remind you how to code up our instructions, then you may leave them there. But don't assume your code is well-commented because you copied our comments.
Create three more functions like swapRedBlue that edit the colors in a Pixmap to achieve some effect. See if you can emulate some of the Instagram effects.
Create a new script, warhol.py, for your main program. It will read in one image, create four copies of it, use your manipulation functions to change their colors, create a new blank image that is width*2 by height*2 and then use the putPixmap function to insert the four edited images. Finally, it should write out the collage image.
```
def main(commandLineStrings):
    # if the length of commandLineStrings is less than 2
        # print a usage statement
        # exit

    # read in the Pixmap from commandLineStrings[1], put the result into a variable (e.g. pixmap)
    # clone pixmap and assign it to a new variable (e.g. map1)
    # clone pixmap and assign it to a new variable (e.g. map2)
    # clone pixmap and assign it to a new variable (e.g. map3)
    # clone pixmap and assign it to a new variable (e.g. map4)

    # call your first manipulator function on map1
    # call your second manipulator function on map2
    # call your third manipulator function on map3
    # call your fourth manipulator function on map4

    # create a new Pixmap that is 2*width x 2*height and store it in a new variable

    # put map1 into the collage at (x, y) = (0, 0)
    # put map2 into the collage at (0, height)
    # put map3 into the collage at (width, 0)
    # put map4 into the collage at (width, height)

    # save the big map to a file
```
Finish up this task by putting a call to main inside the conditional statement we've used before. Then call your python program and view the collage.

Tip: For this function, helpful comments would indicate the different sections of code (e.g. "read in one pixmap", "make 4 copies of it", "make an empty pixmap big enough to hold 4 copies of this one", and "put the 4 filtered images into the big one"). And, of course, a docstring is a must.

Important: You'll want to add the pictures to your writeup, but the wiki doesn't support the .ppm format. There are two ways to get around this problem. The first is to take a screenshot like we've done in the past and upload that instead.

Alternatively, you can use some cool image-manipulation software installed on the lab machines. (Sadly, it isn't automatically built into Mac OS X the same way python is.) To do this, use convert at the command line like so:

$ convert myImage.ppm myImage.png

You can even resize it this way:

$ convert myImage.ppm -scale 25% mySmallerImage.png

More information about convert is available at the ImageMagick web site.
Your last task is to create a python program that reads in your blue-screen image and turns the blue-screen pixels to a different color. The rest of the pixels should remain untouched. You will need to loop over each pixel in the image and test if it is very blue. If it is very blue, change its color. Otherwise, leave it alone.
A reasonable test for 'very blue' is if the blue channel is at least twice the red channel and also bigger than the green channel.

Extensions

Create a larger or more complex Warhol style collage. Place the images in a pattern more complicated than that of a square (but not random!).
Do something more interesting than a single color to replace the blue screen.
Place yourself in a scene. Start with a background scene that is the same size image as your blue-screen image. Then copy only non-blue pixels from your images into the background. You can do this by making a version of putPixmap that copies only non-blue pixels. You could call it putPixmapWithoutBlue.
Enable your Warhol program to read in multiple images from the command line and make a collage for each one, or a collage that integrates several images.
Make a function or functions that modify the image based on one or more parameters and demonstrate that you can make several different output images by varying the parameter.
Use a Python language feature new to you (not just a new library feature or function)

Writeup and Hand-In

Before handing in your code, double check that it is well-styled:

All file names use the case we requested.
All variable names and function names use either camelCase or snake_case.
All functions and files have docstrings. (One nice way to check this is to generate the documentation webpages and see that they contain everything.)
Comments are added to explain complicated code blocks.
All variable and function names are appropriately descriptive.
Functions are defined before any other code is added at the top level of each file.
Top level code is wrapped so that it won't execute if that file is imported by another.

Make a new wiki page for your assignment. Put the label cs151s14project4 on the page. Each of you needs to make your own writeup.

In addition to making the wiki page writeup, put the python files you wrote on the Academics server in your private handin directory.

Colby Wiki

In general, your writeup should follow the outline below.

A brief summary of the task, in your own words. This should be no more than a few sentences. Give the reader context and identify the key purpose of the assignment.
A description of your solution to the tasks, including any images you created. (Make sure your images are appropriately sized to fit onto the wiki page.) This should be a description of the form and functionality of your final code. You may want to incorporate code snippets in your description to point out relevant features. Note any unique computational solutions you developed.
A description of any extensions you undertook, including images demonstrating those extensions. If you added any modules, functions, or other design components, note their structure and the algorithms you used.
A brief description (1-3 sentences) of what you learned.
A list of people you worked with, including students who took the course in previous semesters, TAs, and professors. Include in this list anyone whose code you may have seen. If you didn't work with anyone, please say so.
Don't forget to label your writeup so that it is easy for others to find. For this lab, use cs151s14project4