最近項目輕松了一些，就抱著學習的態度閱讀了HTML Canvas 2D Context的內容。又想到以前曾經在Android上做過原筆跡手寫的內容，就想試著在HTML5中簡單做一下看看。摸索著完成了demo。下面是在Google Chrome 13.0版本上的效果。
下面附上代碼，僅僅為學習，沒做優化，作為例子吧。
注：要在支持HTML5的浏覽器上運行才能看到效果。
- <html>
- <head>
- <title>write demo</title>
- </head>
- <body>
- <canvas width="800" height="450"></canvas>
- <script>
- var canvas = document.getElementsByTagName('canvas')[0];
- canvas.addEventListener('mousemove', onMouseMove, false);
- canvas.addEventListener('mousedown', onMouseDown, false);
- canvas.addEventListener('mouseup', onMouseUp, false);
-
- var context = canvas.getContext('2d');
- var linex = new Array();
- var liney = new Array();
- var linen = new Array();
-
- var lastX = -1;
- var lastY = -1;
- var hue = 0;
- var flag = 0;
-
- function onMouseMove(evt) {
- if (flag == 1) {
- linex.push(evt.layerX);
- liney.push(evt.layerY);
- linen.push(1);
- context.save();
- context.translate(context.canvas.width/2, context.canvas.height/2);
- context.translate(-context.canvas.width/2, -context.canvas.height/2);
- context.beginPath();
- context.lineWidth = 5 + Math.random() * 10;
-
- for (var i=1;i<linex.length;i++) {
- lastX = linex[i];
- lastY = liney[i];
- if (linen[i] == 0) {
- context.moveTo(lastX,lastY);
- } else {
- context.lineTo(lastX,lastY);
- }
- }
-
- huehue = hue + 10 * Math.random();
- context.strokeStyle = 'hsl(' + hue + ', 50%, 50%)';
- context.shadowColor = 'white';
- context.shadowBlur = 10;
- context.stroke();
- context.restore();
- }
- }
- function onMouseDown(evt) {
- flag = 1;
- linex.push(evt.layerX);
- liney.push(evt.layerY);
- linen.push(0);
- }
- function onMouseUp(evt) {
- flag = 0;
- linex.push(evt.layerX);
- liney.push(evt.layerY);
- linen.push(0);
- }
- </script>
- </body>
- </html>
