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Canvas Paint Demo
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| <!doctype html> | |
| <html> | |
| <head> | |
| <meta charset="UTF-8"> | |
| <title>History API & Canvas Demo</title> | |
| <style> | |
| #canvas{ display: block; width: 300px; height: 300px; border: 1px solid #000; } | |
| #color-selector{ display: block; margin:10px 0; height: 25px; line-height: 25px; } | |
| #color-selector > span{ | |
| display: inline-block; width: 20px; height: 20px; margin-right: 5px; cursor: pointer; | |
| } | |
| .black{ background-color: black; } | |
| .red{ background-color: red; } | |
| .orange{ background-color: orange; } | |
| .cyan{ background-color: cyan; } | |
| .blue{ background-color: blue; } | |
| .green{ background-color: green; } | |
| .magenta{ background-color: magenta; } | |
| </style> | |
| </head> | |
| <body> | |
| <canvas id="canvas" width="300" height="300"></canvas> | |
| <div id="color-selector"> | |
| <span class="black"></span> | |
| <span class="red"></span> | |
| <span class="orange"></span> | |
| <span class="cyan"></span> | |
| <span class="blue"></span> | |
| <span class="green"></span> | |
| <span class="magenta"></span> | |
| </div> | |
| <button class="back" disabled>復原</button> | |
| <button class="load">讀取</button> | |
| <button class="save">儲存</button> | |
| <button class="clear">清除</button> | |
| <script> | |
| // 初始化設定 | |
| var canvas = document.getElementById('canvas'); | |
| var colors = document.querySelectorAll('#color-selector > span'); | |
| var back = document.querySelector('.back'), | |
| load = document.querySelector('.load'), | |
| save = document.querySelector('.save'), | |
| clear = document.querySelector('.clear'); | |
| if( !localStorage.image ){ load.disabled = true; } | |
| var context = canvas.getContext('2d'); | |
| context.lineWidth = 4; | |
| context.strokeStyle = '#000'; | |
| var isDrawing = false; | |
| var state = context.getImageData(0, 0, canvas.width, canvas.height); | |
| window.history.pushState(state, null); | |
| // 切換顏色 | |
| for( var i = 0; i < colors.length; i++ ){ | |
| colors[i].addEventListener('click', function(){ | |
| context.strokeStyle = this.className; | |
| }, false); | |
| } | |
| // 復原 | |
| back.addEventListener('click', function(){ | |
| window.history.go(-1); | |
| }, false); | |
| // 清除 | |
| clear.addEventListener('click', function(){ | |
| context.clearRect(0, 0, canvas.width, canvas.height); | |
| }, false); | |
| // 儲存 | |
| save.addEventListener('click', function(){ | |
| localStorage.setItem('image', canvas.toDataURL() ); | |
| load.disabled = false; | |
| alert('已儲存'); | |
| }, false); | |
| // 讀取 | |
| load.addEventListener('click', function(){ | |
| var img = new Image(); | |
| img.src = localStorage.getItem('image'); | |
| context.clearRect(0, 0, canvas.width, canvas.height); | |
| context.drawImage(img, 0, 0); | |
| }, false); | |
| // canvas 滑鼠操作事件 | |
| canvas.addEventListener('mousedown', startDarw, false); | |
| canvas.addEventListener('mousemove', drawing, false); | |
| canvas.addEventListener('mouseup', stopDrawing, false); | |
| // popstate 事件 | |
| window.addEventListener('popstate', changeStep, false); | |
| function changeStep(e){ | |
| // 清除畫布 | |
| context.clearRect(0, 0, canvas.width, canvas.height); | |
| if(e.state){ | |
| context.putImageData(e.state, 0, 0); | |
| } | |
| } | |
| function stopDrawing(e){ | |
| isDrawing = false; | |
| back.disabled = false; | |
| var state = context.getImageData(0, 0, canvas.width, canvas.height); | |
| window.history.pushState(state, null); | |
| } | |
| function drawing(e){ | |
| if(isDrawing){ | |
| context.lineTo(e.pageX - canvas.offsetLeft, e.pageY - canvas.offsetTop); | |
| context.stroke(); | |
| } | |
| } | |
| function startDarw(e){ | |
| isDrawing = true; | |
| context.beginPath(); | |
| context.moveTo(e.pageX - canvas.offsetLeft, e.pageY - canvas.offsetTop); | |
| } | |
| </script> | |
| </body> | |
| </html> |
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