• Objective
Practice Git, Java and Eclipse.
• Marking
This exercise will be autotested out of of 10 marks.
It is worth 2% of your nal grade.
The submission deadline is January 22, 2017 11:59pm on GitHub.
This is an individual assignment.
Late submission policy: No late submissions are accepted.
• How to submit your work
1. Please sign in to git using your mail.utoronto.ca account. Use this invitiation link https://classroom.github.com/assignment-invitations/9c3bb8ad2850e234f9085fb1f338c852 and clone the starter code following GitHub instructions.
2. Complete the code for countBlob() method.
3. You may test your work using BlobApp.
4. To submit your work, add, commit and push your changes to your repository.
Do not commit the les and directories generated by Eclipse, such as bin, doc, .project, etc. Marks will be deducted if you submit these.
5. The date and time of your last commit must be on or before 22 Jan 2017, 11:59pm.
• What is a Blob?
In this section we explain what are blobs, how to generate a grid of them, and how to count them. This problem is often encountered in image processing. We consider an image as a rectangle made of pixels, where each pixel is turned on or o , that is each pixel can be black or white. We will model such an image by a grid a characters, where a black pixel is indicated by the presence of letter X in the approriate position, and a white pixel is indicated by the presence of a dot in the relevant position. An important problem in image processing is identifying and labelling connected component of pixels, or blobs.
By de nition, a blob is a contiguous collection of X’s. For example, the grid below contains four di erent blobs which have been outlined.
1
CSC301 Introduction To Software Engineering (
Our goal is to create an application that given a grid, counts and reports the number of blobs. In order to enable you to test, we have provided in the starter code a blob generator.
We have represented a grid internally as a two-dimensional array of boolean values, with true indicating a blob character, and false indicating a non-blob character
• Counting Blobs
In order to successfully count blobs, let’s make the following observations:
A single X character surrounded by non-blob characters is a blob, and, if we have a blob larger than one character, removing a blob character, what remains is again a blob. (What kind of de nition is this?)
Once we have identi ed all characters that do belong to a particular blob, we want to mark them so they do not get counted twice.
A possible solution is to maintain a grid of the same size as the original grid, tentatively called marked, which is going to be used to mark individual cells of the original grid if and only if:
The location does exist; that is it is not outside the boundaries of the grid. The location does contain a blob character.
The location has not already been visited.
Please complete the code for the countBlob() method as required in the starter code.
2
