p5.js p5.Font textBounds() Method

The textBounds() method of p5.Font in p5.js is to return a tight bounding box for the given string using the font it is used upon. This method supports only single lines.
Syntax:

textBounds( line, x, y, [fontSize], [options] )

Parameters: This function accepts five parameters as mentioned above and described below: 

• line: It is a String which denotes the line of text for which the bounding box has to be found.
• x: It is a Number which denotes the x-position.
• y: It is a Number which denotes the y-position .
• fontSize: It is a Number which denotes the font size to be used. The default value is 12. It is an optional parameter.
• options: It is an Object which can be used to specify opentype options. Opentype fonts contain options like alignment and baseline options. The default values are “LEFT” and “alphabetic”. It is an optional parameter.

The examples below illustrates the textBounds() function in p5.js:
Example 1:

javascript

let inputElem;
let currFont;

function preload() {
  currFont = loadFont("fonts/Montserrat.otf");
}

function setup() {
  createCanvas(600, 300);

  textFont(currFont);
}

function draw() {
  clear();
  textSize(16);
  let text1 = "Hello GeeksforGeeks";
  let text2 = "GeeksforGeeks is a computer science portal";
  text("Below is the example of text bounds using 2 font sizes", 20, 20);

  // Set new font size
  let fontSizeSmall = 16;
  textSize(fontSizeSmall);
  // Get the bounding box dimensions
  let bounding_box = currFont.textBounds(text1, 20, 50, fontSizeSmall);
  // Draw the bounding box
  fill(255);
  stroke(0);
  rect(bounding_box.x, bounding_box.y, bounding_box.w, bounding_box.h);
  fill(0);
  noStroke();
  // Show the text
  text(text1, 20, 50);

  // Set new font size
  let fontSizeLarge = 22;
  textSize(fontSizeLarge);
  // Get the bounding box dimensions
  let bounding_box2 = currFont.textBounds(text2, 20, 100, fontSizeLarge);
  // Draw the bounding box
  fill(255);
  stroke(0);
  rect(bounding_box2.x, bounding_box2.y, bounding_box2.w, bounding_box2.h);
  fill(0);
  noStroke();

  text(text2, 20, 100);
}

Output:

Example 2:

javascript

let inputElem;
let currfontSize = 28;
let currFont;

function preload() {
  currFont = loadFont("fonts/Montserrat.otf");
}

function setup() {
  createCanvas(600, 300);

  // Create button to increase font size
  let fontBtn = createButton("Increase Font Size");
  fontBtn.mouseClicked(() => {
    currfontSize += 2;
  });
  fontBtn.position(20, 70);

  // Create input box
  inputElem = createInput("");
  inputElem.position(20, 40);

  textFont(currFont, currfontSize);
}

function draw() {
  clear();
  textSize(18);
  text(
    "Write in input to change the text and observe the bounding box",
    10,
    20
  );

  // Display text and line if input not empty
  let enteredText = inputElem.value();
  if (enteredText != "") {
    // Get the bounding box dimensions
    let bounding_box = currFont.textBounds(enteredText, 20, 150, currfontSize);

    // Show the properties of the boundig box
    text("Box Position X: " + bounding_box.x, 20, 180);
    text("Box Position Y: " + bounding_box.y, 20, 200);
    text("Box Height: " + bounding_box.h, 20, 220);
    text("Box Width: " + bounding_box.w, 20, 240);

    textSize(currfontSize);

    // Set properties for drawing the box
    fill(255);
    stroke(0);

    // Draw the bounding box
    rect(bounding_box.x, bounding_box.y, bounding_box.w, bounding_box.h);
    fill(0);
    noStroke();

    // Show the entered text inside the box
    text(enteredText, 20, 150);
  }
}

Output:

Online editor: https://editor.p5js.org/
Environment Setup: https://www.geeksforgeeks.org/p5-js-soundfile-object-installation-and-methods/amp/
Reference: https://p5js.org/reference/#/p5.Font/textBounds