マウスを使用してHTMLキャンバスに描画したい(例:署名を描画する、名前を描画する...)
どうすればよいですか?ソースコードを教えてください。ありがとうございました
マウスを使用してHTMLキャンバスに描画したい(例:署名を描画する、名前を描画する...)
どうすればよいですか?ソースコードを教えてください。ありがとうございました
回答:
これが実際のサンプルです。
<html>
<script type="text/javascript">
var canvas, ctx, flag = false,
prevX = 0,
currX = 0,
prevY = 0,
currY = 0,
dot_flag = false;
var x = "black",
y = 2;
function init() {
canvas = document.getElementById('can');
ctx = canvas.getContext("2d");
w = canvas.width;
h = canvas.height;
canvas.addEventListener("mousemove", function (e) {
findxy('move', e)
}, false);
canvas.addEventListener("mousedown", function (e) {
findxy('down', e)
}, false);
canvas.addEventListener("mouseup", function (e) {
findxy('up', e)
}, false);
canvas.addEventListener("mouseout", function (e) {
findxy('out', e)
}, false);
}
function color(obj) {
switch (obj.id) {
case "green":
x = "green";
break;
case "blue":
x = "blue";
break;
case "red":
x = "red";
break;
case "yellow":
x = "yellow";
break;
case "orange":
x = "orange";
break;
case "black":
x = "black";
break;
case "white":
x = "white";
break;
}
if (x == "white") y = 14;
else y = 2;
}
function draw() {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = x;
ctx.lineWidth = y;
ctx.stroke();
ctx.closePath();
}
function erase() {
var m = confirm("Want to clear");
if (m) {
ctx.clearRect(0, 0, w, h);
document.getElementById("canvasimg").style.display = "none";
}
}
function save() {
document.getElementById("canvasimg").style.border = "2px solid";
var dataURL = canvas.toDataURL();
document.getElementById("canvasimg").src = dataURL;
document.getElementById("canvasimg").style.display = "inline";
}
function findxy(res, e) {
if (res == 'down') {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.offsetLeft;
currY = e.clientY - canvas.offsetTop;
flag = true;
dot_flag = true;
if (dot_flag) {
ctx.beginPath();
ctx.fillStyle = x;
ctx.fillRect(currX, currY, 2, 2);
ctx.closePath();
dot_flag = false;
}
}
if (res == 'up' || res == "out") {
flag = false;
}
if (res == 'move') {
if (flag) {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.offsetLeft;
currY = e.clientY - canvas.offsetTop;
draw();
}
}
}
</script>
<body onload="init()">
<canvas id="can" width="400" height="400" style="position:absolute;top:10%;left:10%;border:2px solid;"></canvas>
<div style="position:absolute;top:12%;left:43%;">Choose Color</div>
<div style="position:absolute;top:15%;left:45%;width:10px;height:10px;background:green;" id="green" onclick="color(this)"></div>
<div style="position:absolute;top:15%;left:46%;width:10px;height:10px;background:blue;" id="blue" onclick="color(this)"></div>
<div style="position:absolute;top:15%;left:47%;width:10px;height:10px;background:red;" id="red" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:45%;width:10px;height:10px;background:yellow;" id="yellow" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:46%;width:10px;height:10px;background:orange;" id="orange" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:47%;width:10px;height:10px;background:black;" id="black" onclick="color(this)"></div>
<div style="position:absolute;top:20%;left:43%;">Eraser</div>
<div style="position:absolute;top:22%;left:45%;width:15px;height:15px;background:white;border:2px solid;" id="white" onclick="color(this)"></div>
<img id="canvasimg" style="position:absolute;top:10%;left:52%;" style="display:none;">
<input type="button" value="save" id="btn" size="30" onclick="save()" style="position:absolute;top:55%;left:10%;">
<input type="button" value="clear" id="clr" size="23" onclick="erase()" style="position:absolute;top:55%;left:15%;">
</body>
</html>
canvas.offsetLeft;
しcanvas.offsetTop;
ました。canvas.getBoundingClientRect().left;
canvas.getBoundingClientRect().top;
touchmove
、touchstart
、touchend
その後、clientX
から来ているe.touches["0"].clientX
中でfindxy()
、コードのあなたは、私がテストしたものから、同時に両方のイベントに耳を傾けることができないとして、かかわらず、使われているものを検出するための簡単な方法を考えていません。私はそのままにmouseout
した。完璧ではありませんが、機能します
次に、キャンバスを使用して描画アプリケーションを作成する最も簡単な方法を示します。
mousedown
、mousemove
およびmouseup
キャンバスDOMにイベントリスナーをmousedown
、マウス座標を取得し、moveTo()
メソッドを使用して描画カーソルを配置し、メソッドを使用しbeginPath()
て新しい描画パスを開始します。mousemove
、を使用してパスに新しいポイントを継続的に追加しlineTo()
、を使用して最後のセグメントに色を付けstroke()
ます。mouseup
場合、フラグを設定して描画を無効にします。そこから、線の太さ、色、ブラシストローク、さらにはレイヤーを選択する機能をユーザーに提供するなど、他のあらゆる種類の機能を追加できます。
ここにある他の例は複雑すぎると思います。これはシンプルでJSのみ...
// create canvas element and append it to document body
var canvas = document.createElement('canvas');
document.body.appendChild(canvas);
// some hotfixes... ( ≖_≖)
document.body.style.margin = 0;
canvas.style.position = 'fixed';
// get canvas 2D context and set him correct size
var ctx = canvas.getContext('2d');
resize();
// last known position
var pos = { x: 0, y: 0 };
window.addEventListener('resize', resize);
document.addEventListener('mousemove', draw);
document.addEventListener('mousedown', setPosition);
document.addEventListener('mouseenter', setPosition);
// new position from mouse event
function setPosition(e) {
pos.x = e.clientX;
pos.y = e.clientY;
}
// resize canvas
function resize() {
ctx.canvas.width = window.innerWidth;
ctx.canvas.height = window.innerHeight;
}
function draw(e) {
// mouse left button must be pressed
if (e.buttons !== 1) return;
ctx.beginPath(); // begin
ctx.lineWidth = 5;
ctx.lineCap = 'round';
ctx.strokeStyle = '#c0392b';
ctx.moveTo(pos.x, pos.y); // from
setPosition(e);
ctx.lineTo(pos.x, pos.y); // to
ctx.stroke(); // draw it!
}
if (e.buttons !== 1) return;
;-)。
resize
機能が原因である可能性が高いです。キャンバスの幅と高さをウィンドウサイズに基づいて設定しています。これらはに基づいて設定する必要があります<div class="container-fluid">
。
offset
にsetPosition
機能...
これをグーグル化した(「html5キャンバスペイントプログラム」)。必要なもののように見えます。
このhttp://jsfiddle.net/ArtBIT/kneDX/を確認してください。これはあなたを正しい方向に導くはずです
この方法を署名にも使用することを検討していましたが、http://codetheory.in/でサンプルを見つけました。
以下のコードをjsfiddleに追加しました
HTML:
<div id="sketch">
<canvas id="paint"></canvas>
</div>
JavaScript:
(function() {
var canvas = document.querySelector('#paint');
var ctx = canvas.getContext('2d');
var sketch = document.querySelector('#sketch');
var sketch_style = getComputedStyle(sketch);
canvas.width = parseInt(sketch_style.getPropertyValue('width'));
canvas.height = parseInt(sketch_style.getPropertyValue('height'));
var mouse = {x: 0, y: 0};
var last_mouse = {x: 0, y: 0};
/* Mouse Capturing Work */
canvas.addEventListener('mousemove', function(e) {
last_mouse.x = mouse.x;
last_mouse.y = mouse.y;
mouse.x = e.pageX - this.offsetLeft;
mouse.y = e.pageY - this.offsetTop;
}, false);
/* Drawing on Paint App */
ctx.lineWidth = 5;
ctx.lineJoin = 'round';
ctx.lineCap = 'round';
ctx.strokeStyle = 'blue';
canvas.addEventListener('mousedown', function(e) {
canvas.addEventListener('mousemove', onPaint, false);
}, false);
canvas.addEventListener('mouseup', function() {
canvas.removeEventListener('mousemove', onPaint, false);
}, false);
var onPaint = function() {
ctx.beginPath();
ctx.moveTo(last_mouse.x, last_mouse.y);
ctx.lineTo(mouse.x, mouse.y);
ctx.closePath();
ctx.stroke();
};
}());
これが私の非常にシンプルな作業キャンバスの描画と消去です。
https://jsfiddle.net/richardcwc/d2gxjdva/
//Canvas
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
//Variables
var canvasx = $(canvas).offset().left;
var canvasy = $(canvas).offset().top;
var last_mousex = last_mousey = 0;
var mousex = mousey = 0;
var mousedown = false;
var tooltype = 'draw';
//Mousedown
$(canvas).on('mousedown', function(e) {
last_mousex = mousex = parseInt(e.clientX-canvasx);
last_mousey = mousey = parseInt(e.clientY-canvasy);
mousedown = true;
});
//Mouseup
$(canvas).on('mouseup', function(e) {
mousedown = false;
});
//Mousemove
$(canvas).on('mousemove', function(e) {
mousex = parseInt(e.clientX-canvasx);
mousey = parseInt(e.clientY-canvasy);
if(mousedown) {
ctx.beginPath();
if(tooltype=='draw') {
ctx.globalCompositeOperation = 'source-over';
ctx.strokeStyle = 'black';
ctx.lineWidth = 3;
} else {
ctx.globalCompositeOperation = 'destination-out';
ctx.lineWidth = 10;
}
ctx.moveTo(last_mousex,last_mousey);
ctx.lineTo(mousex,mousey);
ctx.lineJoin = ctx.lineCap = 'round';
ctx.stroke();
}
last_mousex = mousex;
last_mousey = mousey;
//Output
$('#output').html('current: '+mousex+', '+mousey+'<br/>last: '+last_mousex+', '+last_mousey+'<br/>mousedown: '+mousedown);
});
//Use draw|erase
use_tool = function(tool) {
tooltype = tool; //update
}
canvas {
cursor: crosshair;
border: 1px solid #000000;
}
<canvas id="canvas" width="800" height="500"></canvas>
<input type="button" value="draw" onclick="use_tool('draw');" />
<input type="button" value="erase" onclick="use_tool('erase');" />
<div id="output"></div>
アルコはこれをチェックします:
例:https :
//github.com/williammalone/Simple-HTML5-Drawing-App
ドキュメント:http :
//www.williammalone.com/articles/create-html5-canvas-javascript-drawing-app/
このドキュメントには、次のコードが含まれています。
HTML:
<canvas id="canvas" width="490" height="220"></canvas>
JS:
context = document.getElementById('canvas').getContext("2d");
$('#canvas').mousedown(function(e){
var mouseX = e.pageX - this.offsetLeft;
var mouseY = e.pageY - this.offsetTop;
paint = true;
addClick(e.pageX - this.offsetLeft, e.pageY - this.offsetTop);
redraw();
});
$('#canvas').mouseup(function(e){
paint = false;
});
$('#canvas').mouseleave(function(e){
paint = false;
});
var clickX = new Array();
var clickY = new Array();
var clickDrag = new Array();
var paint;
function addClick(x, y, dragging)
{
clickX.push(x);
clickY.push(y);
clickDrag.push(dragging);
}
//Also redraw
function redraw(){
context.clearRect(0, 0, context.canvas.width, context.canvas.height); // Clears the canvas
context.strokeStyle = "#df4b26";
context.lineJoin = "round";
context.lineWidth = 5;
for(var i=0; i < clickX.length; i++) {
context.beginPath();
if(clickDrag[i] && i){
context.moveTo(clickX[i-1], clickY[i-1]);
}else{
context.moveTo(clickX[i]-1, clickY[i]);
}
context.lineTo(clickX[i], clickY[i]);
context.closePath();
context.stroke();
}
}
そして、もう一つの素晴らしい例
http://perfectionkills.com/exploring-canvas-drawing-techniques/
この件について簡単な例を提供する必要があったので、ここで共有します。
http://jsfiddle.net/Haelle/v6tfp2e1
class SignTool {
constructor() {
this.initVars()
this.initEvents()
}
initVars() {
this.canvas = $('#canvas')[0]
this.ctx = this.canvas.getContext("2d")
this.isMouseClicked = false
this.isMouseInCanvas = false
this.prevX = 0
this.currX = 0
this.prevY = 0
this.currY = 0
}
initEvents() {
$('#canvas').on("mousemove", (e) => this.onMouseMove(e))
$('#canvas').on("mousedown", (e) => this.onMouseDown(e))
$('#canvas').on("mouseup", () => this.onMouseUp())
$('#canvas').on("mouseout", () => this.onMouseOut())
$('#canvas').on("mouseenter", (e) => this.onMouseEnter(e))
}
onMouseDown(e) {
this.isMouseClicked = true
this.updateCurrentPosition(e)
}
onMouseUp() {
this.isMouseClicked = false
}
onMouseEnter(e) {
this.isMouseInCanvas = true
this.updateCurrentPosition(e)
}
onMouseOut() {
this.isMouseInCanvas = false
}
onMouseMove(e) {
if (this.isMouseClicked && this.isMouseInCanvas) {
this.updateCurrentPosition(e)
this.draw()
}
}
updateCurrentPosition(e) {
this.prevX = this.currX
this.prevY = this.currY
this.currX = e.clientX - this.canvas.offsetLeft
this.currY = e.clientY - this.canvas.offsetTop
}
draw() {
this.ctx.beginPath()
this.ctx.moveTo(this.prevX, this.prevY)
this.ctx.lineTo(this.currX, this.currY)
this.ctx.strokeStyle = "black"
this.ctx.lineWidth = 2
this.ctx.stroke()
this.ctx.closePath()
}
}
var canvas = new SignTool()
canvas {
position: absolute;
border: 2px solid;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<canvas id="canvas" width="500" height="300"></canvas>
質問されて回答されてから数年が経ちました。
簡単な描画キャンバスを探している人(たとえば、ユーザー/顧客から署名をとるなど)のために、現在受け入れられている回答のより単純化されたjqueryバージョンを投稿しています
$(document).ready(function() {
var flag, dot_flag = false,
prevX, prevY, currX, currY = 0,
color = 'black', thickness = 2;
var $canvas = $('#canvas');
var ctx = $canvas[0].getContext('2d');
$canvas.on('mousemove mousedown mouseup mouseout', function(e) {
prevX = currX;
prevY = currY;
currX = e.clientX - $canvas.offset().left;
currY = e.clientY - $canvas.offset().top;
if (e.type == 'mousedown') {
flag = true;
}
if (e.type == 'mouseup' || e.type == 'mouseout') {
flag = false;
}
if (e.type == 'mousemove') {
if (flag) {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = color;
ctx.lineWidth = thickness;
ctx.stroke();
ctx.closePath();
}
}
});
$('.canvas-clear').on('click', function(e) {
c_width = $canvas.width();
c_height = $canvas.height();
ctx.clearRect(0, 0, c_width, c_height);
$('#canvasimg').hide();
});
});
<html>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.0/jquery.min.js"></script>
<body>
<canvas id="canvas" width="400" height="400" style="position:absolute;top:10%;left:10%;border:2px solid;"></canvas>
<input type="button" value="Clear" class="canvas-clear" />
</body>
</html>
これの実装に問題がある場合は、お知らせください。これはprocessing.jsを使用し、色を変更して描画ポイントを大きくしたり小さくしたりするための機能を備えています。
<html>
<head>
<!--script librarires-->
<script type="text/javascript" src="processing.js"></script>
<script type="text/javascript" src="init.js"></script>
<!--styles -->
<style type="text/css" src="stylesheet.css">
</style>
</head>
<body>
<!--toolbox -->
<div id="draggable toolbox"></div>
<script type="application/processing">
// new script
int prevx, prevy;
int newx, newy;
boolean cliked;
color c1 = #000000;
int largeur=2;
int ps = 20;
int px = 50;
int py = 50;
void setup() {
size(500,500);
frameRate(25);
background(50);
prevx = mouseX;
prevy = mouseY;
cliked = false;
}
void draw() {
//couleur
noStroke(0);
fill(#FFFFFF);//blanc
rect(px, py, ps, ps);
fill(#000000);
rect(px, py+(ps), ps, ps);
fill(#FF0000);
rect(px, py+(ps*2), ps, ps);
fill(#00FF00);
rect(px, py+(ps*3), ps, ps);
fill(#FFFF00);
rect(px, py+(ps*4), ps, ps);
fill(#0000FF);
rect(px, py+(ps*5), ps, ps);
//largeur
fill(#FFFFFF);
rect(px, py+(ps*7), ps, ps);
fill(#FFFFFF);
rect(px, py+(ps*8), ps, ps);
stroke(#000000);
line(px+2, py+(ps*7)+(ps/2), px+(ps-2), py+(ps*7)+(ps/2));
line(px+(ps/2), py+(ps*7)+1, px+(ps/2), py+(ps*8)-1);
line(px+2, py+(ps*8)+(ps/2), px+(ps-2), py+(ps*8)+(ps/2));
if(cliked==false){
prevx = mouseX;
prevy = mouseY;
}
if(mousePressed) {
cliked = true;
newx = mouseX;
newy = mouseY;
strokeWeight(largeur);
stroke(c1);
line(prevx, prevy, newx, newy);
prevx = newx;
prevy = newy;
}else{
cliked= false;
}
}
void mouseClicked() {
if (mouseX>=px && mouseX<=(px+ps)){
//couleur
if (mouseY>=py && mouseY<=py+(ps*6)){
c1 = get(mouseX, mouseY);
}
//largeur
if (mouseY>=py+(ps*7) && mouseY<=py+(ps*8)){
largeur += 2;
}
if (mouseY>=py+(ps*8) && mouseY<=py+(ps*9)){
if (largeur>2){
largeur -= 2;
}
}
}
}
</script><canvas></canvas>
</body>
</html>
init.js
?
バニラJavaScriptを含まない、ここでの超短いバージョンposition:absolute
。主なアイデアは、キャンバスのコンテキストを正しい座標に移動して線を引くことです。click
ハンドラーとコメントmousedown
&mousemove
ハンドラーのコメントを解除して、動作を確認してください。
<!DOCTYPE html>
<html>
<body>
<p style="margin: 50px">Just some padding in y direction</p>
<canvas id="myCanvas" width="300" height="300" style="background: #000; margin-left: 100px;">Your browser does not support the HTML5 canvas tag.</canvas>
<script>
const c = document.getElementById("myCanvas");
// c.addEventListener("click", penTool); // fires after mouse left btn is released
c.addEventListener("mousedown", setLastCoords); // fires before mouse left btn is released
c.addEventListener("mousemove", freeForm);
const ctx = c.getContext("2d");
function setLastCoords(e) {
const {x, y} = c.getBoundingClientRect();
lastX = e.clientX - x;
lastY = e.clientY - y;
}
function freeForm(e) {
if (e.buttons !== 1) return; // left button is not pushed yet
penTool(e);
}
function penTool(e) {
const {x, y} = c.getBoundingClientRect();
const newX = e.clientX - x;
const newY = e.clientY - y;
ctx.beginPath();
ctx.lineWidth = 5;
ctx.moveTo(lastX, lastY);
ctx.lineTo(newX, newY);
ctx.strokeStyle = 'white';
ctx.stroke();
ctx.closePath();
lastX = newX;
lastY = newY;
}
let lastX = 0;
let lastY = 0;
</script>
</body>
</html>
キャンバスの背景画像がある場合、白い消去トリックで背景を隠すため、適切に機能するように微調整する必要があります。
ここにコードの要点があります。
<html>
<script type="text/javascript">
var canvas, canvasimg, backgroundImage, finalImg;
var mouseClicked = false;
var prevX = 0;
var currX = 0;
var prevY = 0;
var currY = 0;
var fillStyle = "black";
var globalCompositeOperation = "source-over";
var lineWidth = 2;
function init() {
var imageSrc = '/abstract-geometric-pattern_23-2147508597.jpg'
backgroundImage = new Image();
backgroundImage.src = imageSrc;
canvas = document.getElementById('can');
finalImg = document.getElementById('finalImg');
canvasimg = document.getElementById('canvasimg');
canvas.style.backgroundImage = "url('" + imageSrc + "')";
canvas.addEventListener("mousemove", handleMouseEvent);
canvas.addEventListener("mousedown", handleMouseEvent);
canvas.addEventListener("mouseup", handleMouseEvent);
canvas.addEventListener("mouseout", handleMouseEvent);
}
function getColor(btn) {
globalCompositeOperation = 'source-over';
lineWidth = 2;
switch (btn.getAttribute('data-color')) {
case "green":
fillStyle = "green";
break;
case "blue":
fillStyle = "blue";
break;
case "red":
fillStyle = "red";
break;
case "yellow":
fillStyle = "yellow";
break;
case "orange":
fillStyle = "orange";
break;
case "black":
fillStyle = "black";
break;
case "eraser":
globalCompositeOperation = 'destination-out';
fillStyle = "rgba(0,0,0,1)";
lineWidth = 14;
break;
}
}
function draw(dot) {
var ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.globalCompositeOperation = globalCompositeOperation;
if(dot){
ctx.fillStyle = fillStyle;
ctx.fillRect(currX, currY, 2, 2);
} else {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = fillStyle;
ctx.lineWidth = lineWidth;
ctx.stroke();
}
ctx.closePath();
}
function erase() {
if (confirm("Want to clear")) {
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
document.getElementById("canvasimg").style.display = "none";
}
}
function save() {
canvas.style.border = "2px solid";
canvasimg.width = canvas.width;
canvasimg.height = canvas.height;
var ctx2 = canvasimg.getContext("2d");
// comment next line to save the draw only
ctx2.drawImage(backgroundImage, 0, 0);
ctx2.drawImage(canvas, 0, 0);
finalImg.src = canvasimg.toDataURL();
finalImg.style.display = "inline";
}
function handleMouseEvent(e) {
if (e.type === 'mousedown') {
prevX = currX;
prevY = currY;
currX = e.offsetX;
currY = e.offsetY;
mouseClicked = true;
draw(true);
}
if (e.type === 'mouseup' || e.type === "mouseout") {
mouseClicked = false;
}
if (e.type === 'mousemove') {
if (mouseClicked) {
prevX = currX;
prevY = currY;
currX = e.offsetX;
currY = e.offsetY;
draw();
}
}
}
</script>
<body onload="init()">
<canvas id="can" width="400" height="400" style="position:absolute;top:10%;left:10%;border:2px solid;">
</canvas>
<div style="position:absolute;top:12%;left:43%;">Choose Color</div>
<div style="position:absolute;top:15%;left:45%;width:10px;height:10px;background:green;" data-color="green" onclick="getColor(this)"></div>
<div style="position:absolute;top:15%;left:46%;width:10px;height:10px;background:blue;" data-color="blue" onclick="getColor(this)"></div>
<div style="position:absolute;top:15%;left:47%;width:10px;height:10px;background:red;" data-color="red" onclick="getColor(this)"></div>
<div style="position:absolute;top:17%;left:45%;width:10px;height:10px;background:yellow;" data-color="yellow" onclick="getColor(this)"></div>
<div style="position:absolute;top:17%;left:46%;width:10px;height:10px;background:orange;" data-color="orange" onclick="getColor(this)"></div>
<div style="position:absolute;top:17%;left:47%;width:10px;height:10px;background:black;" data-color="black" onclick="getColor(this)"></div>
<div style="position:absolute;top:20%;left:43%;">Eraser</div>
<div style="position:absolute;top:22%;left:45%;width:15px;height:15px;background:white;border:2px solid;" data-color="eraser" onclick="getColor(this)"></div>
<canvas id="canvasimg" style="display:none;" ></canvas>
<img id="finalImg" style="position:absolute;top:10%;left:52%;display:none;" >
<input type="button" value="save" id="btn" size="30" onclick="save()" style="position:absolute;top:55%;left:10%;">
<input type="button" value="clear" id="clr" size="23" onclick="erase()" style="position:absolute;top:55%;left:15%;">
</body>
</html>