{"id":7809,"date":"2018-07-22T21:14:57","date_gmt":"2018-07-22T13:14:57","guid":{"rendered":"https:\/\/www.zhangxinxu.com\/wordpress\/?p=7809"},"modified":"2018-08-02T01:17:27","modified_gmt":"2018-08-01T17:17:27","slug":"canvas-color-transition","status":"publish","type":"post","link":"https:\/\/www.zhangxinxu.com\/wordpress\/2018\/07\/canvas-color-transition\/","title":{"rendered":"Canvas\u4e2d\u989c\u8272\u8fc7\u6e21\u52a8\u753b\u6548\u679c\u7684\u5b9e\u73b0"},"content":{"rendered":"

by zhangxinxu<\/a> from https:\/\/www.zhangxinxu.com\/wordpress\/?p=7809<\/a>
\n\u672c\u6587\u53ef\u5168\u6587\u8f6c\u8f7d\uff0c\u4f46\u9700\u8981\u4fdd\u7559\u539f\u4f5c\u8005\u548c\u51fa\u5904\u3002<\/p>\n

\u4e00\u3001\u5173\u4e8e\u989c\u8272\u52a8\u753b\u7684\u524d\u8a00<\/h3>\n

\"canvas\u989c\u8272\u8fc7\u6e21\u5904\u7406\u7f29\u7565\u56fe\"<\/p>\n

\u5728CSS3\u4e2d\uff0c\u6211\u4eec\u8981\u60f3\u5b9e\u73b0\u4eceA\u989c\u8272\u5230B\u989c\u8272\u7684\u8fc7\u6e21\u6548\u679c\uff0c\u662f\u76f8\u5f53\u5bb9\u6613\u7684\uff0c\u53ea\u8981\u6307\u5b9a\u8d77\u6b62\u989c\u8272\uff0c\u914d\u5408transition<\/code>\u8fc7\u6e21\u6216\u8005animation<\/code>\u52a8\u753b\u90fd\u53ef\u4ee5\u65f6\u95f4\u6211\u4eec\u60f3\u8981\u7684\u6548\u679c\u3002<\/p>\n

\u4f46\u662f\uff0c\u5728<canvas><\/code>\u4e2d\u5374\u6ca1\u6709\u8fd9\u4e48\u7b80\u5355\uff0c\u56e0\u4e3a<canvas><\/code>\u672c\u8d28\u4e0a\u662f\u4e00\u4e2a\u9759\u6001\u753b\u5e03\uff0c\u8981\u60f3\u5b9e\u73b0\u989c\u8272\u53d8\u5316\uff0c\u9700\u8981JS\u53bb\u4e0d\u65ad\u7ed8\u5236\uff0c\u5b9e\u73b0\u8d77\u6765\u8981\u6bd4CSS\u5b9e\u73b0\u9ebb\u70e6\u5f88\u591a\u3002\u518d\u52a0\u4e0a\u989c\u8272\u503c\u672c\u8eab\u5c31\u4e0d\u4e00\u5b9a\u662f\u7eaf\u7cb9\u7684\u6570\u503c\uff0c\u66f4\u589e\u52a0\u4e86\u6211\u4eec\u5b9e\u73b0\u7684\u96be\u5ea6\u3002<\/p>\n

\u672c\u6587\u5c31\u5c06\u901a\u8fc7\u591a\u4e2a\u6848\u4f8b\uff0c\u9010\u6b65\u6df1\u5165\uff0c\u4ecb\u7ecd\u4e00\u4e9b\u5728Canvas\u4e2d\u7684\u989c\u8272\u5904\u7406\u6280\u5de7\uff0c\u6709\u4e9b\u6280\u5de7\u8bf4\u4e0d\u5b9a\u4f1a\u8ba9\u4f60\u5927\u5f00\u773c\u754c\u3002<\/p>\n

\u4e8c\u3001Canvas\u989c\u8272\u52a8\u753b\u786c\u5b9e\u73b0<\/h3>\n

\u6240\u8c13\u201c\u786c\u5b9e\u73b0\u201d\uff0c\u5c31\u662f\u4e0d\u901a\u8fc7\u201c\u5947\u5de7\u6deb\u6280\u201d\uff0c\u6309\u7167\u6b63\u5e38\u903b\u8f91\uff0c\u4e00\u6761\u8def\u8d70\u5230\u5e95\u7684\u5b9e\u73b0\u65b9\u5f0f\u3002<\/p>\n

\u4f8b\u5982\uff0c\u6211\u4eec\u8981\u5728<canvas><\/code>\u4e2d\u5b9e\u73b0\u4e00\u4e2a\u84dd\u8272\u5230\u7ea2\u8272\u7684\u52a8\u753b\u6548\u679c\uff0c\u601d\u8def\u5982\u4e0b\uff1a<\/p>\n

    \n
  1. \u83b7\u53d6\u84dd\u8272\u548c\u7ea2\u8272\u7684RGB\u8272\u503c\uff1b<\/li>\n
  2. \u4f7f\u7528\u5b9a\u65f6\u5668\uff0c\u914d\u5408\u8fd0\u52a8\u7b97\u6cd5\uff0cR\uff0cG\uff0cB\u6570\u503c\u540c\u65f6\u53d8\u5316\u4ea7\u751f\u53d8\u8272\u3002<\/li>\n<\/ol>\n

    \u5177\u4f53\u5982\u4f55\u5b9e\u73b0\uff0c\u53ef\u4ee5\u53c2\u89c1\u8fd9\u4e2a\u6848\u4f8b\u3002\u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a\u989c\u8272\u6570\u503c\u53d8\u5316\u4e0b\u7684\u989c\u8272\u52a8\u753bdemo<\/a><\/p>\n

    \u5b9e\u73b0\u7684\u6548\u679c\u5982\u4e0bGIF\u622a\u56fe\uff08\u4e0a\u9762\u662fCanvas\u5b9e\u73b0\uff0c\u4e0b\u9762\u662fCSS3\u5b9e\u73b0\uff0c\u65b9\u4fbf\u6548\u679c\u5bf9\u6bd4\uff09\uff1a<\/p>\n

    \"\u786c\u5b9e\u73b0\u7684canvas\u989c\u8272\u53d8\u5316\"<\/p>\n

    \u5b8c\u6574JS\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n

    var canvas = document.getElementById('canvas');\nvar context = canvas.getContext('2d');\nvar width = canvas.width, height = canvas.height;\n\/\/ \u52a8\u753b\u6267\u884c\u7684\u5e27\u6570<\/span>\nvar start = 0, frames = 200;\n\/\/ \u8fc7\u6e21\u989c\u8272 \u84dd\u8272 \u5230 \u7ea2\u8272<\/span>\nvar from = [0, 0, 255];\nvar to = [255, 0, 0];\n\/\/ \u52a8\u753b\u7b97\u6cd5\uff0c\u8fd9\u91cc\u4f7f\u7528Cubic.easeOut\u7b97\u6cd5<\/span>\nvar cubicEaseOut = function(t, b, c, d) {\n    return c * ((t = t\/d - 1) * t * t + 1) + b;\n};\n\/\/ \u7ed8\u5236\u65b9\u6cd5<\/span>\nvar draw = function () {\n    context.clearRect(0, 0, width, height);\n    \/\/ \u8ba1\u7b97\u6b64\u65f6r, g, b\u6570\u503c<\/span>\n    var r = cubicEaseOut(start, from[0], to[0] - from[0], frames);\n    var g = cubicEaseOut(start, from[1], to[1] - from[1], frames);\n    var b = cubicEaseOut(start, from[2], to[2] - from[2], frames);\n    \/\/ \u53ef\u4ee5\u786e\u5b9a\u8272\u503c<\/span>\n    context.fillStyle = 'rgb('+ [r, g, b].join() +')';\n    context.arc(width \/ 2, height \/ 2, height \/ 2, 0, 2 * Math.PI);\n    context.fill();\n    \/\/ \u6301\u7eed\u53d8\u5316<\/span>\n    start++;\n    if (start <= frames) {\n        requestAnimationFrame(draw);    \n    }\n};\ndraw();<\/pre>\n
    \u201c\u786c\u5b9e\u73b0\u201d\u7684\u5c40\u9650\u6240\u5728<\/h4>\n
    \u201c\u786c\u5b9e\u73b0\u201d\u867d\u7136\u57fa\u672c\u6548\u679c\u6709\u4e86\uff0c\u4f46\u662f\u4e5f\u5b58\u5728\u4e00\u4e9b\u5c40\u9650\uff0c\u4e3b\u8981\u5c31\u662f\u6211\u4eec\u524d\u540e\u53d8\u5316\u7684\u8272\u503c\u4e0d\u4e00\u5b9a\u6b63\u597d\u5c31\u662fRGB\u989c\u8272\uff0c\u53ef\u80fd\u662f#RRGGBB<\/code>\u8fd9\u79cd\u5341\u516d\u8fdb\u5236\u8272\u503c\uff0c\u6216\u8005hsl<\/code>\u989c\u8272\uff0c\u8fd9\u4e2a\u8fd8\u597d\uff0c\u6211\u4eec\u53ef\u4ee5\u8272\u503c\u8f6c\u6362\u4e0b\uff08\u8f6c\u6362\u65b9\u6cd5\u53c2\u89c1\u201cHEX\u5341\u516d\u8fdb\u5236\u4e0eRGB, HSL\u989c\u8272\u7684\u76f8\u4e92\u8f6c\u6362<\/a>\u201d\u8fd9\u7bc7\u6587\u7ae0\uff09\uff1b\u8fd8\u6709\u53ef\u80fd\u989c\u8272\u662f\u534a\u900f\u660e\u7684RGBA\u6216\u8005HSLA\u989c\u8272\uff0c\u8fd9\u4e48\u4e5f\u8fd8\u884c\uff0c\u54ac\u54ac\u7259\uff0c\u4e5f\u53ef\u4ee5\u5b9e\u73b0\uff0c\u4e0d\u5c31\u662f\u591a\u4e00\u4e2a\u900f\u660e\u5ea6\u53d8\u5316\u7684\u6570\u503c\u53c2\u6570\u561b\uff1b\u7136\u800c\uff0c\u6700\u6015\u7684\u5c31\u662f\u8272\u503c\u662f147\u4e2a\u989c\u8272\u5173\u952e\u5b57\u4e4b\u4e00<\/a>\uff0c\u4f8b\u5982\u8bf7\u5b9e\u73b0blue<\/code>\u5230red<\/code>\u7684\u6548\u679c\u3002\u662f\u4e0d\u662f\u53ea\u80fd\u671b\u7801\u5174\u53f9\u4e86\u3002<\/p>\n
    \u8272\u503c\u8f6c\u6362\u9ebb\u70e6\uff0c\u5173\u952e\u5b57\u53d8\u5316\u65e0\u80fd\u4e3a\u529b\uff0c\u6709\u6ca1\u6709\u4ec0\u4e48\u6280\u5de7\u53ef\u4ee5\u4e00\u6b21\u6027\u641e\u5b9a\u5462\uff1f\u6709\uff01<\/p>\n
    \u4e09\u3001\u4efb\u610f\u989c\u8272\u8f6cRGB\u8272\u503c\u6280\u5de7<\/h3>\n
    \u6240\u6709web\u6d4f\u89c8\u5668\u6709\u8fd9\u4e48\u4e00\u4e2a\u7279\u6027\uff0c\u5f53\u6211\u4eec\u4f7f\u7528getComputedStyle<\/code>\u539f\u751f\u63a5\u53e3\u53bb\u83b7\u53d6DOM\u5143\u7d20\u7684\u8272\u503c\u7684\u65f6\u5019\uff0c\u8fd4\u56de\u7684\u5168\u90e8\u90fd\u662fRGB\u8272\u503c\u6216\u8005RGBA\u8272\u503c\u3002<\/p>\n
    \u4e3e\u4e2a\u4f8b\u5b50\uff0c\u5982\u4e0bJavaScript\u4ee3\u7801\uff1a<\/p>\n
    var div = document.createElement('div');\ndiv.style.color = 'red';\ndocument.body.appendChild(div);\nconsole.log(window.getComputedStyle(div).color);<\/pre>\n
    \u7ed3\u679c\u662f\uff1argb(255, 0, 0)<\/code><\/p>\n
    \u5e76\u4e0d\u662f'red'<\/code>\u3002<\/p>\n
    \"\u8272\u503c\u8f6cRGB\"<\/p>\n
    \u4e8e\u662f\uff0c\u501f\u52a9\u6d4f\u89c8\u5668\u7279\u6027\uff0c\u65e0\u8bba\u4ec0\u4e48\u989c\u8272\u503c\uff0c\u60f3\u8981\u5728canvas\u4e2d\u6709\u52a8\u753b\u6548\u679c\uff0c\u90fd\u4e0d\u6210\u95ee\u9898\u4e86\u3002\u6211\u4eec\u53ef\u4ee5\u5c01\u88c5\u4e00\u4e2a\u4efb\u610f\u8272\u503c\u8f6cRGBA\u989c\u8272\u7684\u65b9\u6cd5\uff0c\u5982\u4e0b\uff1a<\/p>\n
    \/**\n* \u4efb\u610f\u989c\u8272\u8f6cRGBA\u65b9\u6cd5\n*\/<\/span>\nvar toRGBA = function (color) {\n    \/\/ \u521b\u5efadiv\u5143\u7d20\u5e76\u8bbe\u7f6e\u989c\u8272<\/span>\n    var div = document.createElement('div');\n    div.style.color = color;\n    document.body.appendChild(div);\n    \/\/ \u8fd4\u56de\u8ba1\u7b97\u540e\u7684\u989c\u8272\u503c<\/span>\n    var cssColor = window.getComputedStyle(div).color;\n    \/\/ div\u5143\u7d20\u79fb\u9664<\/span>\n    document.body.removeChild(div);\n    \/\/ \u5982\u679c\u662fRGB\u989c\u8272\uff0c\u5219\u8f6c\u6362\u6210RGBA\u8868\u793a<\/span>\n    var arrRGBA = cssColor.match(\/\\d+\/g);\n    if (arrRGBA.length == 3) {\n        arrRGBA.push(1);\n    }\n    \/\/ \u6bcf\u4e00\u9879\u8f6c\u6362\u6210\u6570\u503c\u7c7b\u578b<\/span>\n    return arrRGBA.map(function (value) {\n        return value * 1;\n    });\n};<\/pre>\n
    \u5b9e\u73b0\u7684\u662f\u6df1\u5929\u7a7a\u84dd'deepskyblue'<\/code>\u5230\u4f69\u5947\u7c89'deeppink'<\/code>\u989c\u8272\u52a8\u753b\u6548\u679c\uff0c\u5982\u4e0bGIF\u793a\u610f\uff1a<\/p>\n
    \"canvas\u5173\u952e\u5b57\u989c\u8272\u8fc7\u6e21\u6548\u679c\"<\/p>\n
    JavaScript\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n
    var canvas = document.getElementById('canvas');\nvar context = canvas.getContext('2d');\nvar width = canvas.width, height = canvas.height;\n\/\/ \u52a8\u753b\u6267\u884c\u7684\u5e27\u6570<\/span>\nvar start = 0, frames = 200;\n\/\/ \u8fc7\u6e21\u989c\u8272 \u5929\u7a7a\u84dd \u5230 \u4f69\u5947\u7c89<\/span>\nvar from = toRGBA('deepskyblue');\nvar to = toRGBA('deeppink');<\/span>\n\/\/ \u52a8\u753b\u7b97\u6cd5\uff0c\u8fd9\u91cc\u4f7f\u7528Cubic.easeOut\u7b97\u6cd5<\/span>\nvar cubicEaseOut = function(t, b, c, d) {\n    return c * ((t = t\/d - 1) * t * t + 1) + b;\n};\n\/\/ \u7ed8\u5236\u65b9\u6cd5<\/span>\nvar draw = function () {\n    context.clearRect(0, 0, width, height);\n    \/\/ \u8ba1\u7b97\u6b64\u65f6r, g, b, a\u6570\u503c<\/span>\n    var r = cubicEaseOut(start, from[0], to[0] - from[0], frames);\n    var g = cubicEaseOut(start, from[1], to[1] - from[1], frames);\n    var b = cubicEaseOut(start, from[2], to[2] - from[2], frames);\n    var a = cubicEaseOut(start, from[3], to[3] - from[3], frames);\n    \/\/ \u53ef\u4ee5\u786e\u5b9a\u8272\u503c<\/span>\n    context.fillStyle = 'rgba('+ [r, g, b, a].join() +')';\n    context.arc(width \/ 2, height \/ 2, height \/ 2, 0, 2 * Math.PI);\n    context.fill();\n    \/\/ \u6301\u7eed\u53d8\u5316<\/span>\n    start++;\n    if (start <= frames) {\n        requestAnimationFrame(draw);    \n    }\n};\ndraw();<\/pre>\n
    \u4f9d\u7136\u5b58\u5728\u7684\u5c40\u9650<\/h4>\n
    \u76ee\u524dCanvas\u4e2d\u4eceA\u8272\u5230B\u8272\u7684\u8fc7\u6e21\u52a8\u753b\u6548\u679c\u5df2\u7ecf\u53ef\u4ee5\u5b9e\u73b0\u4e86\uff0c\u4f46\u662f\uff0c\u5982\u679c\u6211\u4eec\u7684\u989c\u8272\u53d8\u5316\u662f\u4e30\u5bcc\u7684\u6709\u5c42\u6b21\u7684\uff0c\u5219\u6211\u4eec\u7684\u5b9e\u73b0\u53c8\u53d8\u5f97\u9ebb\u70e6\u4e86\u3002<\/p>\n
    \u4f8b\u5982\uff0c\u8981\u5b9e\u73b0\u7ea2\u6a59\u9ec4\u7eff\u9752\u84dd\u7d2b7\u8272\u6e10\u53d8\uff0c\u4e14\u6bcf\u79cd\u8fc7\u6e21\u6240\u5360\u65f6\u95f4\u90fd\u4e0d\u4e00\u6837\uff0c\u8be5\u600e\u4e48\u529e\uff1f<\/p>\n
    \u5982\u679c\u662fCSS3\u5b9e\u73b0\uff0c\u5219\u5f88\u7b80\u5355\uff0c\u5b9a\u4e49\u4e00\u4e2aanimation<\/code>\u52a8\u753b\u5c31\u53ef\u4ee5\uff0c\u7c7b\u4f3c\u8fd9\u6837\uff1a<\/p>\n
    @keyframes color {\n    0% { background-color: red; }\n    7% { background-color: orange; }\n   17% { background-color: yellow; }\n   22% { background-color: green; }\n   42% { background-color: cyan; }\n   82% { background-color: blue; }\n   90% { background-color: purple; }\t\n}<\/pre>\n
    \u5982\u679c\u8981\u5728Canvas\u4e2d\u5b9e\u73b0\uff0c\u6211\u53bb\uff0c\u4e0d\u6562\u60f3\u8c61\uff0c\u4ee3\u7801\u4f30\u8ba1\u4f1a\u5f88\u5570\u55e6\u3002\u6709\u6ca1\u6709\u4ec0\u4e48\u7b80\u5355\u53d6\u5de7\u7684\u65b9\u6cd5\u5b9e\u73b0\u590d\u6742\u989c\u8272\u52a8\u753b\u6548\u679c\u5462\uff1f\u6709\uff01<\/p>\n
    \u56db\u3001\u501f\u52a9CSS3\u5b9e\u73b0\u590d\u6742canvas\u52a8\u753b<\/h3>\n
    \u65e0\u8bba\u662fCSS3 transition<\/code>\u8fc7\u6e21\u6216\u8005animation<\/code>\u52a8\u753b\uff0c\u6211\u4eec\u90fd\u53ef\u4ee5\u4f7f\u7528JS\u5b9e\u65f6\u8fd4\u56de\u5f53\u524d\u52a8\u753b\u4e2d\u7684\u989c\u8272\u503c\u7b49CSS\u5c5e\u6027\u503c\uff0c\u4e8e\u662f\uff0c\u6211\u4eec\u6839\u672c\u5c31\u4e0d\u9700\u8981\u5728Canvas\u4e2d\u201c\u786c\u5b9e\u73b0\u201d\u52a8\u753b\u6548\u679c\uff0c\u76f4\u63a5\u628aDOM\u4e2d\u7684\u53d8\u5316\u91cf\u5b9e\u65f6\u8d4b\u503c\u5c31\u597d\u4e86\u3002<\/p>\n
    \u60a8\u53ef\u4ee5\u72e0\u72e0\u5730\u70b9\u51fb\u8fd9\u91cc\uff1a\u501f\u52a9CSS3 animation\u5b9e\u73b0canvas\u989c\u8272\u52a8\u753bdemo<\/a><\/p>\n
    \u6548\u679c\u5982\u4e0bGIF\uff1a<\/p>\n
    \"canvas\u4e03\u5f69\u989c\u8272\u52a8\u753b\"<\/p>\n
    \u6211\u4eec\u7684DOM\u5143\u7d20\uff08\u4e0bJS\u4ee3\u7801\u4e2d\u7684eleShape<\/code>\uff09\u5e94\u7528CSS3\u52a8\u753b\uff1a<\/p>\n
    .shape.active {\n    animation: color 3.33s both;\t\n}<\/pre>\n
    JS\u4ee3\u7801\u5c31\u7b80\u5355\u591a\u4e86\uff0c\u5b9e\u65f6\u8272\u503c\u4e00\u81f4\u5373\u53ef\uff1a<\/p>\n
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