Randomly select color from a list of preset colors

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cattmalla..

Randomly select color from a list of preset colors

in Programming Questions • 9 months ago

Hey, complete noob here. I'm trying to create a pixel grid that is composed of a set of preselected colors, and that randomly distributes these colors throughout the grid. here is some code that I have already written, hopefully this will help to illustrate what I am trying to do:

float x = 0;

while(x<width) {

float y = 0;

while(y<height) {

if (random(100)> 50) { //50% chance that the square will be grayscale

fill( random(40, 200), random(30, 200), random(200));}

else{

fill(random(50, 250));

}

rect(x, y, 40, 40);

y = y + 40;

}

x = x + 40;

}

Currently, my program selects randomly from a spectrum of colors, and this is not what I want. Any help is greatly appreciated.

Replies(5)

calsign

Re: Randomly select color from a list of preset colors

9 months ago

If you want a list of colors to select from, then you can use an array.
The format for creating that would be as follows:

color[] colorList = {color(255, 0, 0), color(0, 255, 0), etc...}; //Creates a list of colors. Add more in a comma-separated list...

Then, you can pick a random color from that list by accessing a random element of the array:

color randomColor = colorList[random(colorList.length)]; //Assigns randomColor to be a random color from colorList

I'm not going to go as far as to implement this directly into your code, but if you need more help, please ask for it. Basically, you need to replace the reference to the color (e.g. fill()) with the randomly assigned color.

Also, you could improve your code a bit.

Instead of using while loops, you can use for loops, which are optimal for this situation (progressive, incremental counting). So the main structure of your code would look like this:

for(int x = 0; x < width; x += 40) { //Takes care of creating x, incrementing x, and repeating until it reaches the width
//etc.
}

When you increment a number, it is cleaner and more compact to use the += operator instead of the generic x = x + 1 statement. I have used that in the for loop above. Essentially, it adds the number on the right to the number on the left.

Lastly, when you check for a 50% chance of being a greyscale color, you can simplify the fraction that you use ( 50 / 100) to 1 / 2. This isn't necessarily all that important, but it can make the code easier to read.

cattmalla..

Re: Randomly select color from a list of preset colors

9 months ago

thanks for the quick response!

I tried to implement your advice in my code, but keep getting an error that says "cannot convert float to int" on this line:

color randomColor = colorList[random(colorList.length)]; //Assigns randomColor to be a random color from colorList

Here is what I have changed in the code so far:

color[] colorList = {color(108, 171, 125), color(107, 174, 73), color(79, 184, 87), color(94, 190, 128), color(76, 184, 91), color(53, 170, 89), color(143, 194, 63)}; //Creates a list of colors. Add more in a comma-separated list...

color randomColor = colorList[random(colorList.length)]; //Assigns randomColor to be a random color from colorList

void setup() {

size(400, 400);

noStroke();

background(23, 100, 240);

}

void draw() {

}

void keyReleased() {

int x = 0;

while(x<width) {

int y = 0;

while(y<height) {

if (random(100)> 50) { //50% chance that the square will be grayscale

fill( randomColor);}

else{

fill(red);

}

rect(x, y, 40, 40);

y = y + 40;

}

x = x + 40;

}

GoToLoop

Re: Randomly select color from a list of preset colors

9 months ago

Array indices, the ones inside [ ], must be a whole value!
Function random() generates a fractional float-type value!

There are some functions which can convert a data type into another.
But my preferred method is to use the cast operator instead.
And for our intents here, this specific cast operator serves us best -> (int).
But the other whole ones also work as array index-> (byte), (short), (char). Except -> (long).

Here's the fixed code line:

color randomColor = colorList[ (int) random(colorList.length) ];


P.S.: This post has an example program which heavy-use color constants.

cattmalla..

Re: Randomly select color from a list of preset colors

9 months ago

awesome, thanks a ton!

calsign

Re: Randomly select color from a list of preset colors

9 months ago

Your code, as it appears now, will generate a grid of tiles that are all the same color because you only pick a random color once. Instead, move the picking of the random color to inside the for loop...

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