Question 45297 in Html Question posted in
Some basic documentation can be found here.

Canvas – Line is not being drawn correctly – Html

i want to let my users to draw their signatures to approve that they accept my user agreements. I created canvas and javascript code, but instead of drawing under the mouse, it draws next to it.

You can see how it works here:

https://streamable.com/lz9h1z

JS CODE:

// Select the canvas element
const canvas = document.getElementById('signature-pad');
const ctx = canvas.getContext('2d');



// Set up event listeners
let isDrawing = false;
let lastX = 0;
let lastY = 0;

canvas.addEventListener('mousedown', e => {
    isDrawing = true;
    lastX = e.offsetX;
    lastY = e.offsetY;
});

canvas.addEventListener('mousemove', e => {
    if (isDrawing) {
        ctx.beginPath();
        ctx.moveTo(lastX, lastY);
        ctx.lineTo(e.offsetX, e.offsetY);
        ctx.stroke();
        lastX = e.offsetX;
        lastY = e.offsetY;
    }
});

canvas.addEventListener('mouseup', () => {
    isDrawing = false;
});

canvas.addEventListener('mouseout', () => {
    isDrawing = false;
});

// Set up button event listeners
const clearButton = document.getElementById('clear-button');
clearButton.addEventListener('click', () => {
    ctx.clearRect(0, 0, canvas.width, canvas.height);
});

const saveButton = document.getElementById('save-button');
saveButton.addEventListener('click', () => {
    const dataURL = canvas.toDataURL();
    console.log(dataURL);
});

HTML CODE:

                        <canvas id="signature-pad" width="400" height="200"></canvas>

I was trying to do something with offsets but still no idea.

Tags:

2

Answers


  1. 0

    You can get the mouse position using this code

    function getMouse(e) {
  var rect = canvas.getBoundingClientRect();
  mouseX = (e.clientX - rect.left) / (rect.right - rect.left) * canvas.width,
  mouseY = (e.clientY - rect.top) / (rect.bottom - rect.top) * canvas.height;
}

    Check out the replit here: https://VeneratedJovialCryptos.hackinggo306.repl.co

    Login or Signup to reply.
  2. 0

    I have create an html file with the JS that is related just to the canvas, and everything works as expected. Here is the code:

    <!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <canvas id="signature-pad" width="400" height="200"></canvas>
    
    <script>
        // Select the canvas element
        const canvas = document.getElementById('signature-pad');
        const ctx = canvas.getContext('2d');

        // Set up event listeners
        let isDrawing = false;
        let lastX = 0;
        let lastY = 0;

        canvas.addEventListener('mousedown', e => {
            isDrawing = true;
            lastX = e.offsetX;
            lastY = e.offsetY;
        });
        canvas.addEventListener('mousemove', e => {
            if (isDrawing) {
                ctx.beginPath();
                ctx.moveTo(lastX, lastY);
                ctx.lineTo(e.offsetX, e.offsetY);
                ctx.stroke();
                lastX = e.offsetX;
                lastY = e.offsetY;
            }
        });

        canvas.addEventListener('mouseup', () => {
            isDrawing = false;
        });

        canvas.addEventListener('mouseout', () => {
            isDrawing = false;
        });
    </script>
</body>

</html>

    Here is the result of running this html file: https://streamable.com/69bwa9

    So you can try to place this code in a separate file, and see if everything works- if yes, then you should look for a problem in other parts of the code, if still no, maybe if is something about differences between physical machines, I am trying this on Mac.

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search