Processing: Creative Coding and Computational Art

This sketch outputs the following:
c1 = 2147483392
binary(c1) = 1111111111111111111111100000000
show 32 bits = 01111111111111111111111100000000
binary(c1>>16) = 111111111111111
show 32 bits = 00000000000000000111111111111111
Notice that I explicitly added zeros to the left of two of the binary outputs (labeled show
32 bits) just to reveal the actual 32 bits of data. Again, the zeros on the left of the number
don’t change the number’s value (and thus normally aren’t output when you call
println()), but seeing them does make it easier to visually compare the different binary
bit strings. The color I began with, c1, had an alpha of 127, giving the color integer a
positive value (2147483392) since the signed bit was a zero. Thus, when I shifted all the bits
16 places to the right, the 16 places emptied on the left side of the number were filled
with zeros—again following the rule that the signed bit controls what these values
should be.
Bitwise operators
Please note, when shifting to the left, places emptied on the
right (due to the shifting) are always filled with zeros.
In addition to bit shifting, the original expression float r = myColor >> 16 & 0xFF; contains
a bitwise operator (&) as well as what’s referred to as a bit mask (0xFF).
Bitwise operators are similar to other operators you know about (+, *, -, etc.), only bitwise
operators work directly on binary numbers. There are four bitwise logical operators in
Java, two of which are included in Processing. However, as Processing really is Java, you can
use all four in Processing, even though the Processing language reference only covers two
of them. As I mentioned, these operators work on binary values (directly with the bits). So
if I write 4 | 6, using the bitwise OR operator (which I’ll explain shortly), the numbers 4
and 6 will be evaluated as their binary equivalents (100 and 110, respectively). This is great
for the computer, which loves (assuming it could actually feel) dealing at the bit level, but
kind of lousy for us squishy bio-forms, who are not used to doing fast base 2 calculations.
It helps to see the bitwise operators in action to get a better sense of how they work.
The four logical bitwise operators are &, |, ^, and ~.
& is the bitwise AND operator; it works by evaluating the parallel bits of two binary numbers.
If the two parallel bits are both 1, then the result for that place is a 1. All other results
evaluate out to 0 for that bit position.
The following example compares the parallel bits of the binary values of 4 and 6 (which
are listed next) using the bitwise AND operator:
MATH REFERENCE
767
B