Lab 2
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## Overview Prior to smartphones and tablets, parents resorted to flattened wood pulp and sticks of colored wax to occupy their kids' attention. One popular App for paper and crayons was called "Connect the Dots" or "Dot to Dot." The "screen" consisted of a collection of numbered dots. The user was required to draw lines between consecutive dots. If the user worked the App correctly, a piece of art emerged. In this assignment you will enhance your solution from [Lab 1](Lab1) to create a generator for dot-to-dot games. ## Assignment Your program must: * Incorporate feedback from your instructor from lab 1 * Indicate the total number of dots in the selected file * Allow the user to enter a desired number of dots * Use the algorithm described below to remove the least critical dots from the picture * Display the picture produced by removing all but the user-specified number of dots * Save a picture to a `.dot` file Note: If the user loads a picture with 2,000 dots, then enters 100 for the desired number of dots, and subsequently enters 1,000 for the desired number of dots, your program must show a picture 1,000 dots, not 100. Here are a few additional sample `.dot` files that your program must be able to load successfully: [balloon.dot](balloon.dot), [dove.dot](dove.dot), and [skull.dot](skull.dot). ## Details ### Calculating the Critical Value of a Dot The critical value of a dot depends on the relative proximity of it and its immediate neighbors. Consider three dots, labeled 1, 2, and 3, on a straight line. If dot 2 is removed, the connect the dots version of the line from 1 to 3 will look exactly the same. Therefore, we can conclude that the dot is not critical. If dot 2 is significantly far from the line connecting dot 1 and 3, then error would be introduced if dot 2 is eliminated. The following figure illustrates this: <figure>[![Critical Value Illustration](lab2cv.png)](lab2cv.png)<figcaption>Figure 1: Critical Value Illustration</figcaption></figure> The critical value of dot 2 is calculated as the sum of the distances from dot 2 to dot 1 and from dot 2 to dot 3 minus the distance from dot 1 to dot 3, i.e., $cv\_2 = d\_{12} + d\_{23} - d\_{13}$ where $cv\_y$ is the critical value for dot $y$ and $d\_{xz}$ are the distances illustrated below. <figure>[![Critical Value Calculation](lab2calc.png)](lab2calc.png)<figcaption>Figure 2: Critical Value Calculation</figcaption></figure> Note that in the case of a straight line between dots 1 and 3, $cv\_2 = 0$ Your program should assume that the first and the last dots are connected so they should be treated as neighbors when calculating their critical values. ### Software Design You must implement `double calculateCriticalValue(Dot previous, Dot next)` in your `Dot` class which returns the critical value for the dot based on the neighboring dots that are passed to the method. In addition, you must remove all constructors from the `Picture` class and implement the following constructors: * **`Picture(List<Dot> emptyList)`** &mdash; Constructor that uses the list `emptyList` passed to it to store the dots for this picture. * **`Picture(Picture original, List<Dot> emptyList)`** &mdash; Constructor that copies the dots from `original` into `emptyList` and uses it to store the dots for this picture. These constructors provide flexibility in our `Picture` class because we can now specify the specific implementation of the `List` used (e.g., `ArrayList`, `LinkedList`, or even our own `List` implementation) by passing the appropriate list to the constructor. In fact, the `Picture` class is no longer dependent on any concrete list implementation. You must also implement the following methods in the `Picture` class: * **`void save(File file)`** &mdash; saves the picture to `.dot` file that is compatible with the format described in [lab 1](Lab1). * **`void removeDots(int numberDesired)`** &mdash; removes all but the `numberDesired` most critical dots. * If the picture does not have more than `numberDesired` dots, the method returns without changing the picture. * If `numberDesired < 3`, an `IllegalArgumentException` is thrown. Your implementation of this method must be consistent with this flow chart: <figure>[![Dot Removal Algorithm Flowchart](lab2flowchart.png)](lab2flowchart.png)<figcaption>Figure 3: Dot Removal Algorithm Flowchart</figcaption></figure> ## Just For Fun Ambitious students may wish to: * Try replacing `lineTo()` with `quadraticCurveTo()` or `bezierCurveTo()`. * Add number annotations next to each dot. * Use shades of colors to indicate the order in which to connect the dots. * Create an option to print the picture. * Overlay the reduced-dot picture on top of the picture with all the dots in the file. You may wish to display the original picture in a lighter color. ## Lab Deliverables > See your professor's instructions for details on submission guidelines and due dates. > * Dr. Taylor's students: See below > * All other students should refer to Blackboard > > If you have any questions, consult your instructor. ## Acknowledgment This laboratory assignment, developed by [Dr. Chris Taylor](/taylor/), is motivated by the seventh programming project in chapter 2 of our textbook which is based on the paper: L. J. Latecki and R. Lakamper, "Convexity Rule for Shape Decomposition Based on Discrete Contour Evolution," *Computer Vision and Image Understanding (CVIU)* 73(1999), pp. 441-454.

Friday, 09-Mar-2018 14:57:05 EST