Homework 4
16-311 Introduction to Robotics
Fall-05. Prof. Howie Choset

Due in class Tue, Sep. 20st
Please answer the following questions. Hand in a hard copy in class. No webpage necessary, and no need to email Robert anything (my inbox is full enough as it is).
  • (70%) Group: Braitenburg Vehicles
  • (30%) Individual:

    Convolution: Individual Work (but learning from each other is encouraged)

    Write a C program conv.c to perform convolution. Your program should input two pgm file names from the keyboard: one for the image and one for the mask. Write a function that convolves the mask with the image. The size of the input and output images should be the same. To make things easier, you will not have to worry about padding the edges of the input image, as discussed in class. Instead, we will just accept that the right-most and bottom-most pixels in the output image will be "wrong." In other words, if the input image has r rows and c columns and the mask has m rows and n columns, the output image will have r rows and c columns but the first r-m+1 rows and c-n+1 columns will have the output. Simply put zeros in the remaining rows and columns.

    Update:
    There may be some confusion about the FlipMask routine in the code provided for homework 4. Basically, this routine takes the input mask and rotates it about the origin by 180 degrees. Why? Well, as you might remember from class, convolution technically requires the mask to be flipped. If you don't flip the mask, the operation is called correlation. Many members of the vision community use the two interchangeably, which is why we told you not to worry about flipping the mask. In the starter code provided, we flipped the mask. You can opt to simply comment this out or you can use the convensional/signal processing version of convolution and flip the mask -- it is your choice. However, for the masks and images provided, it really doesn't make much difference--do you know why? Please be careful; it is easy to get confused, but resolving this confusion will have a nice payoff!

    The masks (as .pgm files)
    Mask #1
    Mask #2
    Mask #3

    The images to convolve:
    zebra.pgm
    horse.pgm

    Use your program to perform convolution on the two images provided with each of the three masks provided for a total of six images. Please hand in a hard copy of all the pictures. You do not have to display them on your webpage unless you want to. Please link your code to your andrew webspace and write the address on the hardcopy you turn in. Do not turn in a printout of the code.

    Also answer the following questions.