Canvas实现放大镜效果完整案例分析(附代码)HTML5 Canvas实现放大镜效果示例canvas离屏技术与放大镜实现代码示例

 //定义canvas画布 var canvas1 = document.getElementById('canvas1'); ctx1 = canvas.getContext('2d'); //模糊图片加载 var image1 = new Image(); image1.src = "./模糊.png"; //图片加载成功后绘制图片 image1.onload = function() { //drawImage 在画布上绘制模糊图片 ctx1.drawImage(image1, 0, 0, canvas1.width, canvas1.height); }; 

 var canvas2 = document.getElementById('canvas2'), ctx2 = canvas2.getContext('2d'), scale = 2; // 放大倍数 // canvas2的图片大小是模糊图片的2倍 canvas2.width = canvas.width * scale; canvas2.height = canvas.height * scale; // 在canvas2中加载图片 var image2 = new Image(); image2.src = "name2.png"; image2.onload = function() { ctx2.drawImage(image2, 0, 0, canvas2.width, canvas2.height); };

 // 保存当前状态 ctx1.save(); // 边框 ctx1.strokeStyle = "#9eddf1"; ctx1.lineWidth = 3; // 开始绘制 ctx1.beginPath(); // ⚪ ctx1.arc(x, y, mr, 0, Math.PI * 2); ctx1.stroke(); // 表示剪切 ctx1.clip(); // 画图 ctx1.drawImage(that.canvas2, sx, sy, 2 * mr, 2 * mr, dx, dy, 2 * mr, 2 * mr); // 释放当前状态 ctx1.restore(); 

 // 圆的半径是mr var mr = 100; // 对应模糊图的左上角起点 var dx = x - mr, dy = y - mr; // 找出清晰图截图的左上角起点 var sx = x * scale - mr, sy = y * scale- mr; 

 ... ctx.clip(); // 在对应的位置上重新绘制图片 //drawImage(img,sx,sy,swidth,sheight,x,y,width,height) 9个参数时 //img: 图片/canvas //sx: 图片的X起点 //sy: 图片的Y起点 //swidth:要绘制的图片选取的宽度 //sheight:要绘制的图片选取的高度 //x,y:图片在canvas上显示的位置 //width,height:在Canvas上要显示的大小 ctx1.drawImage(canvas2, sx, sy, 2 * mr, 2 * mr, dx, dy, 2 * mr, 2 * mr); ...

 //定义一个判断鼠标是否是点击滑动的标识符 var flag; //鼠标点入事件 canvas.onmousedown = function(e) { flag = true; //显示放大镜 } // 鼠标移动事件 canvas.onmousemove = function(e) { if (flag) { //显示放大镜 } } //鼠标松开事件 canvas.onmouseup = function(e) { flag = false; // 隐藏放大镜 } //鼠标离开事件 canvas.onmouseout = function(e) { flag = false; // 隐藏放大镜 }

 var scale = 3; var mr = 150; var photo = { //初始化 init: function() { var that = this; that.canvas = document.getElementById('canvas'); that.ctx = that.canvas.getContext('2d'); that.canvas2 = document.getElementById('canvas2'); that.ctx2 = that.canvas2.getContext('2d'); that.canvas.width = 800; that.canvas.height = 500; that.canvas2.width = that.canvas.width * scale; that.canvas2.height = that.canvas.height * scale; that.image1 = new Image(); that.image1.src = "./name3.jpg"; that.image2 = new Image(); that.image2.src = "./name4.jpg"; that.image1.onload = function() { that.ctx.drawImage(that.image1, 0, 0, that.canvas.width, that.canvas.height); }; that.image2.onload = function() { that.ctx2.drawImage(that.image2, 0, 0, that.canvas2.width, that.canvas2.height); that.moveEvt(); }; }, bigerImage: function(x, y) { var that = this; var imageX = x * scale, imageY = y * scale, sx = imageX - mr, sy = imageY - mr; var dx = x - mr, dy = y - mr; that.ctx.save(); that.ctx.strokeStyle = "#9eddf1"; that.ctx.lineWidth = 3; that.ctx.beginPath(); that.ctx.arc(x, y, mr, 0, Math.PI * 2); that.ctx.shadowColor = "#6ed25b"; that.ctx.shadowBlur = 10; that.ctx.stroke(); that.ctx.clip(); that.ctx.drawImage(that.canvas2, sx, sy, 2 * mr, 2 * mr, dx, dy, 2 * mr, 2 * mr); that.ctx.restore(); }, //移动 moveEvt: function() { var that = this; that.canvas.onmousedown = function(e) { that.flag = true; that.showImage(e); } that.canvas.onmousemove = function(e) { if (that.flag) { that.showImage(e) } } that.canvas.onmouseup = function(e) { that.hideImage(e) } that.canvas.onmouseout = function(e) { that.hideImage(e) } }, showImage: function(e) { e.preventDefault() var x = e.offsetX, y = e.offsetY, that = this; that.ctx.clearRect(0, 0, that.canvas.width, that.canvas.height); that.ctx.drawImage(that.image1, 0, 0, that.canvas.width, that.canvas.height); that.bigerImage(x, y); }, hideImage: function(e) { e.preventDefault() var that = this; that.flag = false; that.ctx.clearRect(0, 0, that.canvas.width, that.canvas.height); that.ctx.drawImage(that.image1, 0, 0, that.canvas.width, that.canvas.height); } } window.onload = function() { photo.init(); }