Lecture1/2: More about RGB & Canvas classes, Your First Digital Image

Add exception handling (use throw, and try & catch blocks) to the two overloaded [] operators of RGB class.

for index under(over)flow.
for color component overflow(>1.0).

Overload +, += operators on RGB class. The + operator adds two RGB objects componentwise.

The signature of the first two methods are

   RGB& operator+=(RGB const& rhs);      // Changes this object, so it is non-const method, and return reference to this object which is the result.
   RGB operator+(RGB const& rhs) const;  // No changes to this object, so it is a const method, and return an (temparary) object which is the result.

When you implement the second method, you should use the first one.

Overload << operator for RGB class, so that we can print out the current red, green, and blue components of the color object.

 ostream& operator<<(ostream& os, RGB const& rgb);

This overloaded function cannot be a member function of the RGB class; it has to be a global function. Usually we declare it as a friend of the RGB class.

Add to RGB class.

a member function which can answer whether there is any overflow of its three components.
a member function which clamps every overflowed component to 1.0.
a member function which does nothing if there is no everflow, and otherwise, scale uniformly each component so that the maximal component is 1.0.

Our overloaded [] operator member function of Canvas can only check the under(over)flow of row numbers, but cannot do anything about colum number under(over)flow because it knows nothing about the colum number.

For example, assuming the canvas is of 16 by 16 size, expression "canvasObj[0][-1]" accesses an invalid address, and expression "canvasObj[0][16]" is logically wrong though it accesses a valid address(why?); however, in either case, our member function fails to report any error.

Try to write another function to access the pixel of the canvas, and do error checking for both row and colum numbers. (Hint, you have to give up [] operator overloading.)

Create a file called xmath.h, which is intended for any of your global math functions extending the C math library. For this class, try to write two math functions, one rounding, the other interpolating. Some examples are,

         round(1.2) = 1, round(1.7) = 2; round(1.5) = 2; round(-1.3) = -1; round(-1.5) = -2;
         interpolate(0.3, 10, 20) = (1-0.3) * 10 + 0.3 * 20 = 13.
         interpolate(0.5, 10, 20) = (1-0.5) * 10 + 0.5 * 20 = 15.
         interpolate(0.7, 10, 20) = (1-0.7) * 10 + 0.7 * 20 = 17.

The signatures are,

          int round(double);
          double interpolate(double t, double x1, double x2);

You have just written the function,

 double interpolate(double t, double x1, double x2);

Now try to do interpolation between two RGB colors.

We have two interpolation functions now, one interpolating between two double numbers to get some number in between them, and the other interpolating between two RGB colors to get some color in between them (color blending). Use C++ template to write a single template function to do both jobs (and potentially more).

Lecture1/2: More about RGB & Canvas classes, Your First Digital Image

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Project 1: Your First Digital Image.