p5.js alpha() function

The alpha() function in p5.js is used to extract the alpha value from a color or pixel array.

Syntax:

alpha(c)

Parameters: The function accepts single parameter as mentioned above and described below:

c : This parameter stores the p5.Color object, color components, or CSS color.

Below program illustrates the alpha() function in p5.js:
Example-1:

function setup() {
    
    //create Canvas of size 300*80  
    createCanvas(300, 80);
}
  
function draw() {
    background(220);
    
    //initialize the parameter  
    let c = color(0, 126, 255, 102);
    
    //extract the alpha value
    let y = alpha(c);
    textSize(16);
    fill(color('red'));
    text("Alpha Value is : " + y, 50, 30);
}

Output:

Example-2:

function setup() {
    
    //create Canvas of size 300*80  
    createCanvas(160, 180);
}
  
function draw() {
    background(220);
    
    //initialize the parameter  
    let c = color(0, 126, 255, 34);
    
    // Sets 'value' to 34
    let value = alpha(c);
    fill(value);
    rect(50, 15, 35, 70);
    text("Value of alpha is : " + value, 22, 110);
}