p5.js alpha() function

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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); 
} 