CSE 101 -- Spring 2021

CSE 101 -- Prog 0

Due before midnight, Sunday, October 03, 2021.
Late submissions will not be accepted/graded.

Change Log:

Oct 03, 2021: The rubric section has been updated.
Sep 29, 2021: Clarification on zipping: You zip the prog0 folder. You do this from the directory that contains the prog0 folder, not while you're in the prog0 folder itself.
Sep 29, 2021: Regarding submissions: You can submit multiple times. Each time, you should get a couple lines of confirmation like:
```
1 File submitted: 
  prog0.zip (revision XXX)
```
You can also confirm your submission by going to (using cd command): /afs/cats.ucsc.edu/class/cse101-ap.f21/prog0/your-cruzid

Objectives:

Brush up on C and recursion. You will also need to brush up a bit on geometry (lines and slopes) and learn a bit of computer graphics along the way.

Description:

In this programming assignment, you will be generating graphics patterns procedurally. Specifically, you will be writing code to draw successively smaller squares. Each smaller square starts off a fraction along the edge of its larger version. Note that there are multiple implementation options e.g. iterative and rotating a smaller version of the larger squares. However, for this assignment, you are required to implement a recursive version. And rather than using rotations, you will have to use fractions. See input requirements below.

Details:

You will read from stdin, which you can redirect from a file. Input will consist of:
- dimension of image - 2 integers, representing width (number of columns) and height (number of rows). Coordinates of points on the image are 0..W-1, 0..H-1. The origin is at the top left corner.
- recursive depth - an integer,
- fraction - a double (between 0 and 1),
- starting point - 2 doubles (x and y coordinates),
- ending point - 2 doubles (x and y coordinates).
In the following examples, input/output pairs are:
- 512 512 5 0.1 50.0 460.0 460.0 460.0
- 512 512 10 0.1 50.0 460.0 460.0 460.0
- 512 512 20 0.1 50.0 460.0 460.0 460.0
- 512 512 40 0.1 50.0 460.0 460.0 460.0
Input for the next image is: 512 512 40 0.9 50.0 460.0 460.0 460.0 Notice how the inner squares appear to rotate the other way from the previous image.
In the 1st image, input consists of: 512 512 8 0.2 50.0 460.0 460.0 460.0. Note that the color was changed as a function of level. Changing colors is not required.
Note that the starting and ending point do not have to be horizontal such as the examples above. The pattern does not need to be centered in the image either (the graphics library will automatically handle cropping off the pattern that's outside the specified image dimension). The example below has the pattern occupying roughly the upper left quadrant of space. Input for the next image is: 512 512 15 0.1 50.0 200.0 250.0 125.0
Requirements:
- In addition to handling the input specifications mentioned above, your output should consist of a solid background color, and a solid foreground color (for drawing your boxes). The examples above use a white background and a red foreground color. You can change these two colors, but please pick a pair that are easy to see.
- The starting and ending points specify an edge of the outermost box. The remaining edges of the box should be drawn in counter-clockwise order.
- Each run of your code should produce a png file.
Graphics Library: There's only a limited number of free simple 2D graphics library with C binding. For this programming assignment, we will use the Cairo Graphics Library. It's easy to learn the basics needed for this assignment and it also supports multiple output "targets". For this assignment, your program will output images in png format. It also runs on multiple platform: Unix, Windows, Mac.
The Cairo Graphics Library is already installed on our campus unix webserver: unix.ucsc.edu. Please make sure that your code compiles, runs, and produces the correct output on this server before submitting your code.

Tutorial/Startup code:

Cairo Tutorial is a nice concise tutorial.
Makefile
Startup code

Geometry review:

The slope of the line connecting points P1 and P2 is H/W, where H = P2.y - P1.y, and W = P2.x - P1.x.
This means that you can "go" from P1 to P2 by adding W along the x-axis (i.e. P2.x = P1.x + W), and adding H along the y-axis (i.e. P2.y = P1.y + H).
You can also move part way instead of all the way. For example, to go 10% of the way towards P2, P.x = P1.x + 0.1*W and P.y = P1.y + 0.1*H, where P is a point between P1 and P2 and 10% from P1.
If the slope of a line is H/W, the the slope of a line perpendicular to that would be -W/H.
The equations above assumes x increases to the right and y increases going up. The coordinate system in Cairo graphics has y increasing going down. You will need to adjust your signs appropriately.

Naming:

Please make sure to name your compiled executable as prog0.

Input/Output:

You will be reading input to your program from stdin. To run your code, we will be doing something like:
prog0 < input1.txt.
The input files will contain the input specs mentioned above prepended by an output filename. Each input file will contain info for a single run. For example, input1.txt might contain:
output1 512 512 5 0.1 50.0 460.0 460.0 460.0.
It should then generate output1.png which contains the output image of your run. Use blank space character as delimiter for the filename.

Grading:

Rubric:

You start off with 100 points.
You lose credit for missing functionality, incorrect results,
poorly documented or formatted code, or not following instructions.

Below is a partial list:

- up to 10 points off for inadequate comments or hard-to-read code
- up to 10 points off for special handling to grade your homework
  (usually because you did not check that it runs on the computers in the lab first)
- up to 10 points off for not following instructions e.g. improper zip file
- functionality points depending on importance
	*  20 points off if not using recursion
	*  10 points off if failed a test (we have 6 test input)

Make sure you:
a.  include a makefile, .c file, and optionally .h file
b.  generate an executable file called prog0 with your makefile
c.  have confirmed that it compiles and runs properly on unix.ucsc.edu
d.  followed the general instructions described in overview.html

Who graded your assignment based on first letter of your CRUZID:
(i.e. who to contact if you have questions about how your program was graded)
```
bryan:	a*  - ju*
nathan:	jw* - z*
```

Submission:

Make sure that you've compiled and tested your code on the campus unix timeshare before submitting. On the unix timeshare, put materials in a folder named prog0 and zip it up.

submit cse101-ap.f21 prog0 prog0.zip

You can submit as often as you want up until the deadline. We will only look at your most recent submission.

After each submission, you should get a message like:

Submitting the files you specified...
copying prog0.zip

1 File submitted: 
  prog0.zip (revision XXX)

where XXX is the number of times you have submitted.

Read the instructions on how to submit your work.