✎ fp:lab07 [books]

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====== L07. For expressions ======

In this lab, we will use matrices to encode Bitmap images. The format is called BPM, and more details are available [[https://en.wikipedia.org/wiki/Netpbm#File_formats|here]]. Our format will be grayscale only. Each pixel of the matrix is encoded as an integer, with values from 0 to 255. Some examples are shown below:

<code>
    0 0 1 0 0
    0 1 0 1 0
    0 1 1 1 0    letter A
    1 0 0 0 1
    1 0 0 0 1
    
    5 4 3 2 1
    5 4 3 2 1
    5 4 3 2 1    shader
    5 4 3 2 1
    5 4 3 2 1
</code>

Add the following type definition for the rest of your lab:
<code scala>
type Img = List[List[Int]]
</code>

Also, in order to benefit from visualisation, instead of using a worksheet, you can create a new Scala project, containing an object with a main method:
<code scala>
object Matrix {
// define your functions here

  def main(args: Array[String]) = {
  // write your tests here
  }
}
</code> 

**7.1.** Write a function