<!doctype html>
<html>

<head>
    <title>Canvas HTML5</title>
    <style>
        #canvas {
            border: 1px solid black;
        }
    </style>
</head>

<body>
    <canvas id="canvas" width="600" height="400"></canvas>
    <div>
        <button class="save">Save</button>
        <button class="clear">clear</button>
        <span>Color: <input type="color" value="#ffff00" id="penColor"></span>
        <span>Width: <input type="range" min="1" max="20" value="10" id="penWidth"></span>
    </div>
    <div class="output"></div>
    <script>
        const canvas = document.querySelector('#canvas');
        const ctx = canvas.getContext('2d');
        const penColor = document.querySelector('#penColor');
        const penWidth = document.querySelector('#penWidth');
        const btnSave = document.querySelector('.save');
        const btnClear = document.querySelector('.clear');
        const output = document.querySelector('.output');
        const mLoc = {
            draw: false, x: 0, y: 0, lastX: 0, lastY: 0
        };
        canvas.style.border = '1px solid black';
        btnSave.addEventListener('click', saveImg);
        btnClear.addEventListener('click', clearCanvas);

        canvas.addEventListener('mousemove', (e) => {
            mLoc.lastX = mLoc.x;
            mLoc.lastY = mLoc.y;
            //console.log(e);
            mLoc.x = e.clientX;
            mLoc.y = e.clientY;
            draw();
        })

        canvas.addEventListener('mousedown', (e) => {
            mLoc.draw = true;
        })
        canvas.addEventListener('mouseup', (e) => {
            mLoc.draw = false;
        })
        canvas.addEventListener('mouseout', (e) => {
            mLoc.draw = false;
        })

        function saveImg() {
            const dataURL = canvas.toDataURL();
            console.log(dataURL);
            const img = document.createElement('img');
            output.prepend(img);
            img.setAttribute('src', dataURL);
            const link = document.createElement('a');
            output.append(link);
            let fileName = Math.random().toString(16).substr(-8) + '.png'
            link.setAttribute('download', fileName);
            link.href = dataURL;
            link.click();
            output.removeChild(link);
        }
        function clearCanvas() {
            let temp = confirm('clear canvas?');
            if (temp) {
                ctx.clearRect(0, 0, canvas.width, canvas.height);
            }
        }

        function draw() {
            if (mLoc.draw) {
                ctx.beginPath();
                ctx.moveTo(mLoc.lastX, mLoc.lastY);
                ctx.lineTo(mLoc.x, mLoc.y);
                ctx.strokeStyle = penColor.value;
                ctx.lineWidth = penWidth.value;
                ctx.stroke();
                ctx.closePath();
            }
        }
    </script>
</body>

</html>
