javaScript canvas實現(畫筆大小顏色橡皮的執行個體)，javascriptcanvas

最後更新：2017-12-05 來源：互聯網

上載者：User

創建阿里雲帳戶，並獲得超過 40 款產品的免費試用版；而企業帳戶則可以享有總值 $1200 的免費試用版。立即註冊！

執行個體如下所示：

<!DOCTYPE html><html> <head> <meta charset="utf-8" /> <title></title> </head> <body> <div> <div>  <!--<input type="button" id="open" value="open"></input> <input type="button" id= "save" value = "save"></input> <input type="button" id= "color" value="color"></input> --> <input type="button" value="size"></input> <input type="text" id="size" onchange="sizeChange()"></input> <input type="button" id="clear" value="clear"></input> <input type="button" id="eraser" value="eraser" onclick="doEraser()"></input> <select id = "shape" onchange="shapeChange()">  <option value = "99">shape</option>  <option value = "1">rectangle</option>  <option value = "0">circle</option>  <option value = "2">line</option> </select>  <input id="color" type="color"/> </div> <canvas id="myCanvas" style=" border:1px solid;" width="800" height="500"></canvas> </div> </body> <script language="JavaScript"> var shap = 99; //0 is circle; 1 is rectangle var orignalX, orignalY;//the coordinate of mouse down var lastX, lastY;//the coordinate of last mouse position var isMouseDown = false; // flag of mouse pressing down var myCanvas = document.getElementById("myCanvas"); var context = myCanvas.getContext('2d'); var width = myCanvas.width, height = myCanvas.height; var data;//storing last canvas' content context.strokeStyle = "black"; context.strokeWidth=1; context.lineWidth = 1;  document.getElementById('color').onchange = function(){   context.strokeStyle = this.value };  function doEraser(){ context.strokeStyle = "white"; shap = 2; } function sizeChange(){  context.lineWidth = parseInt(document.getElementById('size').value);  }  function shapeChange(){ context.strokeStyle = "black";  var myselect = document.getElementById("shape"); var index=myselect.selectedIndex ;  var myvalue = myselect.options[index].value; var mytext=myselect.options[index].text;  shap = parseInt(myvalue);   }  function myCanvasMouseDown(event) { //event.preventDefault();  if(event.button == 0) { orignalX = event.offsetX; orignalY = event.offsetY; context.moveTo(orignalX,orignalY);  data = context.getImageData(0, 0, width, height); isMouseDown = true;  } } function myCanvasMouseMove(event) { if (isMouseDown){ //event.preventDefault();  switch(shap){  case 0:   context.clearRect(0,0,width,height);  context.putImageData(data,0,0);  lastX = event.offsetX;  lastY = event.offsetY;  context.beginPath();  context.arc(orignalX+(lastX-orignalX)/2,orignalY+(lastY-orignalY)/2,Math.abs(lastX-orignalX)/2,0,Math.PI * 2,true);  context.stroke();  context.closePath();  break;  case 1:  context.clearRect(0,0,width,height);  context.putImageData(data,0,0);  lastX = event.offsetX;  lastY = event.offsetY;  context.strokeRect(orignalX, orignalY, lastX-orignalX, lastY-orignalY);  break;  case 2:   lastX = event.offsetX;   lastY = event.offsetY;   context.lineTo(lastX, lastY); //根據滑鼠路徑繪畫    context.stroke(); //立即渲染    break;   } } } function myCanvasMouseUp(event) { if (isMouseDown){ //event.preventDefault();  context.clearRect(0,0,width,height); context.putImageData(data,0,0); lastX = event.offsetX; lastY = event.offsetY; switch(shap){  case 0:  context.beginPath();  context.arc(orignalX+(lastX-orignalX)/2,orignalY+(lastY-orignalY)/2,Math.abs(lastX-orignalX)/2,0,Math.PI * 2,true);  context.stroke();  context.closePath();  break;  case 1:  context.beginPath();  context.strokeRect(orignalX, orignalY, lastX-orignalX, lastY-orignalY);  context.closePath();  break;  case 2:    context.lineTo(lastX, lastY); //根據滑鼠路徑繪畫    context.stroke(); //立即渲染     break; } isMouseDown = false; lastX = null; lastY = null; orignalX = null; orignalY = null; data = context.getImageData(0, 0, width, height); context.beginPath(); context.clearRect(0,0,width,height); context.putImageData(data,0,0); context.closePath(); } }  myCanvas.addEventListener("mousedown", myCanvasMouseDown, false); myCanvas.addEventListener("mousemove", myCanvasMouseMove, false); myCanvas.addEventListener("mouseup", myCanvasMouseUp, false); </script> </html>

以上這篇javaScript canvas實現(畫筆大小顏色橡皮的執行個體)就是小編分享給大家的全部內容了，希望能給大家一個參考，也希望大家多多支援幫客之家。

本文章原先以中文撰寫並發佈於 aliyun.com，亦設英文版本，僅作資訊用途。本網站不對文章的準確性，完整性或可靠性或其任何翻譯作出任何明示或暗示的陳述或保證。如對該文章有任何疑慮或投訴，請傳送電郵至 info-contact@alibabacloud.com 並提供相關疑慮或投訴的詳細說明。職員會於 5 個工作天內與您聯絡，一經驗證之後，即會刪除該侵權內容。

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

Get Started for Free

Sales Support

1 on 1 presale consultation

Chat Contact Sales
After-Sales Support

24/7 Technical Support 6 Free Tickets per Quarter Faster Response

Open a Ticket
Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.

Learn More