Hexadecimal values and bitwise operators.

[Suman Sharma]

Can anyone explain me what is happening in each line of these two methods?

          // Read-only property accessor
   public String getRgbHex() {
      int i = getRGB() & 0xffffff;
      return Integer.toString(i, 16);
   }
 
   // Get complementary color
   public String getRgbComplement() {
      int i =
         ((255 - getRed()) << 16) |
         ((255 - getGreen()) << 8) |
         (255 - getBlue());
      return Integer.toString(i, 16);
   } 

Thank you.

[Kaydell Leavitt]

This first method masks off the alpha channel.

int i = getRGB() & 0xffffff;

If you count the number of f's in the mask, there are 6, each of which is 4 bits wide. This is a 24 bit mask. Each color in RGB is 8 bits times three which is also 24 bits. The 8 bits that is left over is the "alpha channel". The alpha channel contains non-color information such as transparency:

Alpha Channel

return Integer.toString(i, 16);

The above code converts the RGB color value to a hexadecimal String (base 16).

The following code calculates the complementary color:

public String getRgbComplement() {
    int i =
    ((255 - getRed()) << 16) |
    ((255 - getGreen()) << 8) |
     (255 - getBlue());
  return Integer.toString(i, 16);
} 

In the above code, there is no need to mask out the alpha channel because the RGB codes are fetched individually and the alpha channel is never here.

Kaydell

[Suman Sharma]

Thank you for your help.