Processing: Creative Coding and Computational Art

of this part of the API. These mysterious terms relate to bitwise operations. Bitwise operations
are low-level operations useful for squeezing some extra performance out of a
sketch, but they’re also a little (actually more than a little) confusing to use. I cover bitwise
operations further in Appendix B.
Processing has a convenient data type called color that encapsulates the 32 bits of information
making up a color (8 bits for alpha, 8 bits for red, 8 bits for green, and 8 bits for
blue). You can declare a variable of type color using the following syntax:
color c
In the Image section of the API, which I’ll look at next, is a function named get(). get()
returns a value as a color data type based on a specific pixel’s color. Another way to create
a color from scratch is to use the color() function. (I realize it gets confusing when a
number of different commands/data types share common names). Finally, you can create
a color by directly assigning a hexadecimal value to a color variable. Following are three
statements that generate a color three different ways: through the use of get(), through
the use of the color() function, and through direct assignment using hexadecimal notation.
I also include a fourth direct assignment statement that includes an alpha component
in the hexadecimal notation.
color c1 = get(50, 50);
color c2 = color(200, 100, 50);
color c3 = #FF33DD;
// this last statement explicitly specifies alpha and RGB values
color c4 = 0xFFFF33DD;
The Creating & Reading subsection also includes two color-blending functions:
blendColor() and lerpColor(). blendColor(), the more complex of the two functions,
utilizes a blending mode, declared as an argument passed to the function, along with the
two colors to blend. lerpColor() uses a simpler numeric ratio for blending two colors.
Here’s an example that uses both functions, including blendColor()’s different blending
modes (see Figure A-16):
/* blendColor and lerpColor
Ira Greenberg, October 12, 2006 */
size(210, 490);
background(100);
noStroke();
smooth();
color c1 = color(200, 10, 200);
color c2 = color(200, 200, 10);
//blend
color c_add = blendColor(c1, c2, ADD);
color c_subtract = blendColor(c1, c2, SUBTRACT);
color c_darkest = blendColor(c1, c2, DARKEST);
color c_lightest = blendColor(c1, c2, LIGHTEST);
PROCESSING LANGUAGE API
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A