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p5.js | alpha() function
  • Last Updated : 12 Apr, 2019

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);
    }

    Output:

    Reference: https://p5js.org/reference/#/p5/alpha




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