I'm working on an image editor and I'm about to implement filters. I decided to go with some kind of blur or noise.
Anyway, I decided I wanted a uniform filter so I read up on Random.nextGaussian().
However, since I'm working with RGB values that range from 0 to 255. How can I scale this random double value to fit within 0 and 255?
The random value returned by the nextGaussian() can range from -1 to 1 I believe.
So, I want to preserve the relative difference between the random values. "Scale" or "move the number range" if that makes sense.
I know it's possible but I can't figure it out. Thanks in advance.
Essentially, I need it to be a number between 0 and 1.
In that case you should use nextDouble().
The Gaussian distribution is a distribution that ranges over the entire collection of double values (mathematically speaking, from minus infinity to positive infinity) with a peak around zero. The Gaussian distribution is thus not uniform.
The nextDouble() method draws numbers uniformly between 0 and 1 (0 included, 1 excluded).
You can thus draw a number randomly between 0 and 255 (both inclusive) using the following code:
Random rand = new Random();
int value = (int) math.floor(256.0*rand.nextDouble());
A faster algorithm is however masking a random integer (Random.nextInt):
Random rand = new Random();
int value = rand.nextInt()&0xff;
This algorithm isn't faster in big-oh analysis, but it saves one the more expensive nextDouble method call as well as a floating point multiplication and a float-to-int conversion.