Homework

1
Homework1-Part1

• Write a code that reads, records, and outputs
  images encoded in PGM file format.
• We want an object-oriented implementation.
• Thus, we will define a new type (a class) called
  image by specifying its private (or protected)
  and public parts.
• We may proceed by separating the class interface
  (image.h) from the class implementation
  (image.cpp).
• The interface represents the class design and
  tells us what can be done to the new type.

2
Homework1-Part1

• The implementation represents the internals of
  how this is accomplished.
• It is useful to imagine the raw data as a
  rectangle with r rows and c columns.
• A pixel has screen coordinates (x, y), where x
  is in the range 0,c-1 and y is in the range
  0,r-1.
• The rows are numbered from top to bottom and the
  column from left to right.
• However, we generally store the raw data as a
  one-dimensional array with index values from 0 to
  rc -1.

3
Homework1-Part1

• If the data is stored row by row in array Data,
  then the index of pixel with coordinates (x, y)
  is yc x.
• The pixel is accessed in the array at position
  Data yc x

4
Prototype (image.h)

• class image
• private
• char fileType //Magic Identifier
• char comment
• int column
• int row
• int greyLevel //Max greyLevel
• float matrix

5
Prototype (image.h)

• public
• image() //Default constructor
• image(int, int) //Constructor
• image() //Destructor
• int read()
• int save()
• int getwidth()
• int getheight()
• float getvalue(int)
• float getvalue(int,int)
• int getmaxgrey()
• int getmingrey()
• void setvalue(float,int)
• void setvalue(float,int,int)

6
Function to implement
1- Write a function that generates a binary image
Out by thresholding a grey level image In with a
threshold th. Prototype void Imthresh(image
In, image Out, float th)

• To test your functions you can use the images in
  the data folder.