{"id":112,"date":"2019-04-23T11:33:17","date_gmt":"2019-04-23T03:33:17","guid":{"rendered":"http:\/\/www.vkalo.com\/?p=112"},"modified":"2019-04-23T11:33:17","modified_gmt":"2019-04-23T03:33:17","slug":"canvas","status":"publish","type":"post","link":"https:\/\/www.vkalo.com\/index.php\/2019\/04\/23\/canvas\/","title":{"rendered":"canvas"},"content":{"rendered":"\n

Canvas\u662fHTML5\u65b0\u589e\u7684\u7ec4\u4ef6\uff0c\u5b83\u5c31\u50cf\u4e00\u5757\u753b\u5e03\uff0c\u4f7f\u7528JavaScript\u5728\u4e0a\u9762\u7ed8\u5236\u5404\u79cd\u56fe\u8868\u3001\u52a8\u753b\u7b49\uff0c\u5b83\u7684\u51fa\u73b0\u4f7f\u5f97\u7a0b\u5e8f\u5458\u4e0d\u518d\u9700\u8981\u901a\u8fc7JS\u4e0eflash\u4ea4\u4e92\u751f\u4ea7\u7f51\u9875\u52a8\u753b\uff0c\u800c\u76f4\u63a5\u901a\u8fc7js\u518dcanvas\u5185\u8fdb\u884c\u4f5c\u56fe\u3002<\/p>\n\n\n


\n<\/canvas><\/p>\n

var canvas = document.getElementById(‘test-canvas’);<\/p>\n\n\n\n

\u901a\u8fc7\u8fd9\u6bb5\u4ee3\u7801\u5c31\u53ef\u4ee5\u83b7\u53d6\u5bf9\u5e94\u7684canvas\u5143\u7d20<\/p>\n\n\n

ctx = canvas.getContext(‘2d’);\/\/\u83b7\u53d6\u4e8c\u7ef4\u5236\u56fe\u5bf9\u8c61
\ngl = canvas.getContext(“webgl”);\/\/\u83b7\u53d6\u4e09\u7ef4\u5236\u56fe\u5bf9\u8c61<\/p>\n\n\n\n

\u5f97\u76ca\u4e0eH5\u5185\u7684webgl\u6807\u51c6\uff0ccanvas\u4e0d\u4ec5\u80fd\u591f\u4f5c\u4e3a\u4e8c\u7ef4\u753b\u5e03\uff0c\u4e5f\u80fd\u4f5c\u4e3a\u4e09\u7ef4\u56fe\u5f62\u7684\u5bb9\u5668\u3002\uff08\u672c\u6587\u4e3b\u8981\u4ecb\u7ecd\u4e8c\u7ef4\u5236\u56fe\u5185\u5bb9\uff09<\/p>\n\n\n\n

canvas\u5236\u56fe\u8fc7\u7a0b\u6709\u70b9\u50cf\u5148\u6311\u9009\u5408\u9002\u7684\u7b14\uff0c\u8c03\u6574\u989c\u8272\uff0c\u7136\u540e\u4e0b\u7b14\u4f5c\u753b\u3002<\/p>\n\n\n\n

canvas\u4e0d\u540c\u4e8eSVG\uff0cSVG\u540c\u6837\u662f\u901a\u8fc7js\u4f5c\u56fe\uff0c\u4f46svg\u4f5c\u56fe\u7ed3\u679c\u4f1a\u751f\u6210\u5bf9\u5e94\u7684svgDOM\uff0c\u56e0\u6b64\u4e00\u6b21\u4f5c\u56fe\u540e\uff0cSVG\u53ef\u4ee5\u83b7\u53d6\u751f\u6210\u7684DOM\u8fdb\u884c\u4fee\u6539\u3002\u800ccanvas\u53ea\u6709\u4e00\u4e2a\u5143\u7d20\u6807\u7b7e\uff0c\u5373canvas\u672c\u8eab\uff0ccanvas\u4f5c\u56fe\u4f9d\u8d56\u4e8e\u50cf\u7d20\uff0c\u751f\u6210\u540e\u7684\u56fe\u5f62\u65e0\u6cd5\u83b7\u53d6\u4fee\u6539\uff0c\u5982\u679c\u5e0c\u671b\u4fee\u6539canvas\u56fe\u7247\uff0c\u5c31\u9700\u8981\u5bf9\u76f8\u5e94\u7684\u50cf\u7d20\u533a\u57df\u8fdb\u884c\u6e05\u695a\u548c\u91cd\u7ed8\u3002<\/p>\n\n\n\n

\u56e0\u6b64\u6211\u628acanvas\u7684api\u5927\u81f4\u5206\u4e3a\u4ee5\u4e0b\u51e0\u7c7b\uff1a<\/p>\n\n\n\n

1.\u6837\u5f0f\u7c7b\u578b<\/h2>\n\n\n\n

\u989c\u8272\u3001\u6837\u5f0f\u548c\u9634\u5f71<\/h3>\n\n\n\n
\u5c5e\u6027<\/th>\u63cf\u8ff0<\/th><\/tr>
fillStyle<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u7528\u4e8e\u586b\u5145\u7ed8\u753b\u7684\u989c\u8272\u3001\u6e10\u53d8\u6216\u6a21\u5f0f\u3002(\u533a\u57df)<\/td><\/tr>
strokeStyle<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u7528\u4e8e\u7b14\u89e6\u7684\u989c\u8272\u3001\u6e10\u53d8\u6216\u6a21\u5f0f\u3002\uff08\u7ebf\uff09<\/td><\/tr>
shadowColor<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u7528\u4e8e\u9634\u5f71\u7684\u989c\u8272\u3002<\/td><\/tr>
shadowBlur<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u7528\u4e8e\u9634\u5f71\u7684\u6a21\u7cca\u7ea7\u522b\u3002<\/td><\/tr>
shadowOffsetX<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u9634\u5f71\u4e0e\u5f62\u72b6\u7684\u6c34\u5e73\u8ddd\u79bb\u3002<\/td><\/tr>
shadowOffsetY<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u9634\u5f71\u4e0e\u5f62\u72b6\u7684\u5782\u76f4\u8ddd\u79bb\u3002<\/td><\/tr>

createLinearGradient()<\/a> <\/td>
\u521b\u5efa\u7ebf\u6027\u6e10\u53d8\uff08\u7528\u5728\u753b\u5e03\u5185\u5bb9\u4e0a\uff09\u3002 <\/td><\/tr>

createPattern()<\/a> <\/td>
\u5728\u6307\u5b9a\u7684\u65b9\u5411\u4e0a\u91cd\u590d\u6307\u5b9a\u7684\u5143\u7d20\u3002 <\/td><\/tr>

createRadialGradient()<\/a> <\/td>
\u521b\u5efa\u653e\u5c04\u72b6\/\u73af\u5f62\u7684\u6e10\u53d8\uff08\u7528\u5728\u753b\u5e03\u5185\u5bb9\u4e0a\uff09\u3002 <\/td><\/tr>

addColorStop()<\/a> <\/td>
\u89c4\u5b9a\u6e10\u53d8\u5bf9\u8c61\u4e2d\u7684\u989c\u8272\u548c\u505c\u6b62\u4f4d\u7f6e\u3002 <\/td><\/tr><\/tbody><\/table>\n\n\n\n

<\/p>\n\n\n\n

\u7ebf\u6761\u6837\u5f0f<\/h3>\n\n\n\n
\u5c5e\u6027<\/th>\u63cf\u8ff0<\/th><\/tr>
lineCap<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u7ebf\u6761\u7684\u7ed3\u675f\u7aef\u70b9\u6837\u5f0f\u3002<\/td><\/tr>
lineJoin<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u4e24\u6761\u7ebf\u76f8\u4ea4\u65f6\uff0c\u6240\u521b\u5efa\u7684\u62d0\u89d2\u7c7b\u578b\u3002<\/td><\/tr>
lineWidth<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u5f53\u524d\u7684\u7ebf\u6761\u5bbd\u5ea6\u3002<\/td><\/tr>
miterLimit<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u6700\u5927\u659c\u63a5\u957f\u5ea6\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n

2.\u5f62\u72b6\u53ca\u6587\u672c<\/h2>\n\n\n\n

\u5f62\u72b6<\/h3>\n\n\n\n

\u77e9\u5f62<\/h4>\n\n\n\n
\u65b9\u6cd5<\/th>\u63cf\u8ff0<\/th><\/tr>
rect()<\/a><\/td>\u521b\u5efa\u77e9\u5f62\u3002<\/td><\/tr>
fillRect()<\/a><\/td>\u7ed8\u5236”\u88ab\u586b\u5145”\u7684\u77e9\u5f62\u3002<\/td><\/tr>
strokeRect()<\/a><\/td>\u7ed8\u5236\u77e9\u5f62\uff08\u65e0\u586b\u5145\uff09\u3002<\/td><\/tr>
clearRect()<\/a><\/td>\u5728\u7ed9\u5b9a\u7684\u77e9\u5f62\u5185\u6e05\u9664\u6307\u5b9a\u7684\u50cf\u7d20\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n

\u8def\u5f84<\/h4>\n\n\n\n
\u65b9\u6cd5<\/th>\u63cf\u8ff0<\/th><\/tr>
fill()<\/a><\/td>\u586b\u5145\u5f53\u524d\u7ed8\u56fe\uff08\u8def\u5f84\uff09\u3002<\/td><\/tr>
stroke()<\/a><\/td>\u7ed8\u5236\u5df2\u5b9a\u4e49\u7684\u8def\u5f84\u3002<\/td><\/tr>
beginPath()<\/a><\/td>\u8d77\u59cb\u4e00\u6761\u8def\u5f84\uff0c\u6216\u91cd\u7f6e\u5f53\u524d\u8def\u5f84\u3002\uff08\u91cd\u7f6e\u65b0\u753b\u7b14\uff09<\/td><\/tr>
moveTo()<\/a><\/td>\u628a\u8def\u5f84\u79fb\u52a8\u5230\u753b\u5e03\u4e2d\u7684\u6307\u5b9a\u70b9\uff0c\u4e0d\u521b\u5efa\u7ebf\u6761\u3002<\/td><\/tr>
closePath()<\/a><\/td>\u521b\u5efa\u4ece\u5f53\u524d\u70b9\u56de\u5230\u8d77\u59cb\u70b9\u7684\u8def\u5f84\u3002\uff08\u5f62\u6210\u95ed\u5408\u56fe\u5f62\uff09<\/td><\/tr>
lineTo()<\/a><\/td>\u6dfb\u52a0\u4e00\u4e2a\u65b0\u70b9\uff0c\u7136\u540e\u5728\u753b\u5e03\u4e2d\u521b\u5efa\u4ece\u8be5\u70b9\u5230\u6700\u540e\u6307\u5b9a\u70b9\u7684\u7ebf\u6761\u3002<\/td><\/tr>
clip()<\/a><\/td>\u4ece\u539f\u59cb\u753b\u5e03\u526a\u5207\u4efb\u610f\u5f62\u72b6\u548c\u5c3a\u5bf8\u7684\u533a\u57df\u3002<\/td><\/tr>
quadraticCurveTo()<\/a><\/td>\u521b\u5efa\u4e8c\u6b21\u8d1d\u585e\u5c14\u66f2\u7ebf\u3002<\/td><\/tr>
bezierCurveTo()<\/a><\/td>\u521b\u5efa\u4e09\u6b21\u8d1d\u585e\u5c14\u66f2\u7ebf\u3002<\/td><\/tr>
arc()<\/a><\/td>\u521b\u5efa\u5f27\/\u66f2\u7ebf\uff08\u7528\u4e8e\u521b\u5efa\u5706\u5f62\u6216\u90e8\u5206\u5706\uff09\u3002<\/td><\/tr>
arcTo()<\/a><\/td>\u521b\u5efa\u4e24\u5207\u7ebf\u4e4b\u95f4\u7684\u5f27\/\u66f2\u7ebf\u3002<\/td><\/tr>
isPointInPath()<\/a><\/td>\u5982\u679c\u6307\u5b9a\u7684\u70b9\u4f4d\u4e8e\u5f53\u524d\u8def\u5f84\u4e2d\uff0c\u5219\u8fd4\u56de true\uff0c\u5426\u5219\u8fd4\u56de false\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n

\u6587\u672c<\/h3>\n\n\n\n
\u5c5e\u6027<\/th>\u63cf\u8ff0<\/th><\/tr>
font<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u6587\u672c\u5185\u5bb9\u7684\u5f53\u524d\u5b57\u4f53\u5c5e\u6027\u3002<\/td><\/tr>
textAlign<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u6587\u672c\u5185\u5bb9\u7684\u5f53\u524d\u5bf9\u9f50\u65b9\u5f0f\u3002<\/td><\/tr>
textBaseline<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u5728\u7ed8\u5236\u6587\u672c\u65f6\u4f7f\u7528\u7684\u5f53\u524d\u6587\u672c\u57fa\u7ebf\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n
\u65b9\u6cd5<\/th>\u63cf\u8ff0<\/th><\/tr>
fillText()<\/a><\/td>\u5728\u753b\u5e03\u4e0a\u7ed8\u5236”\u88ab\u586b\u5145\u7684”\u6587\u672c\u3002<\/td><\/tr>
strokeText()<\/a><\/td>\u5728\u753b\u5e03\u4e0a\u7ed8\u5236\u6587\u672c\uff08\u65e0\u586b\u5145\uff09\u3002<\/td><\/tr>
measureText()<\/a><\/td>\u8fd4\u56de\u5305\u542b\u6307\u5b9a\u6587\u672c\u5bbd\u5ea6\u7684\u5bf9\u8c61\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n

3.\u50cf\u7d20\u63a7\u5236<\/h2>\n\n\n\n

\u8f6c\u6362<\/h3>\n\n\n\n
\u65b9\u6cd5<\/th>\u63cf\u8ff0<\/th><\/tr>
scale()<\/a><\/td>\u7f29\u653e\u5f53\u524d\u7ed8\u56fe\u81f3\u66f4\u5927\u6216\u66f4\u5c0f\u3002<\/td><\/tr>
rotate()<\/a><\/td>\u65cb\u8f6c\u5f53\u524d\u7ed8\u56fe\u3002<\/td><\/tr>
translate()<\/a><\/td>\u91cd\u65b0\u6620\u5c04\u753b\u5e03\u4e0a\u7684 (0,0) \u4f4d\u7f6e\u3002<\/td><\/tr>
transform()<\/a><\/td>\u66ff\u6362\u7ed8\u56fe\u7684\u5f53\u524d\u8f6c\u6362\u77e9\u9635\u3002\uff08\u4f1a\u53e0\u52a0\uff09<\/td><\/tr>
setTransform()<\/a><\/td>\u5c06\u5f53\u524d\u8f6c\u6362\u91cd\u7f6e\u4e3a\u5355\u4f4d\u77e9\u9635\u3002\u7136\u540e\u8fd0\u884c transform()\u3002\uff08\u4e0d\u53e0\u52a0\uff09<\/td><\/tr><\/tbody><\/table>\n\n\n\n

\u50cf\u7d20\u64cd\u4f5c<\/h3>\n\n\n\n
\u5c5e\u6027<\/th>\u63cf\u8ff0<\/th><\/tr>
width<\/a><\/td>\u8fd4\u56de ImageData \u5bf9\u8c61\u7684\u5bbd\u5ea6\u3002<\/td><\/tr>
height<\/a><\/td>\u8fd4\u56de ImageData \u5bf9\u8c61\u7684\u9ad8\u5ea6\u3002<\/td><\/tr>
data<\/a><\/td>\u8fd4\u56de\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5176\u5305\u542b\u6307\u5b9a\u7684 ImageData \u5bf9\u8c61\u7684\u56fe\u50cf\u6570\u636e\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n
\u65b9\u6cd5<\/th>\u63cf\u8ff0<\/th><\/tr>
createImageData()<\/a><\/td>\u521b\u5efa\u65b0\u7684\u3001\u7a7a\u767d\u7684 ImageData \u5bf9\u8c61\u3002<\/td><\/tr>
getImageData()<\/a><\/td>\u8fd4\u56de ImageData \u5bf9\u8c61\uff0c\u8be5\u5bf9\u8c61\u4e3a\u753b\u5e03\u4e0a\u6307\u5b9a\u7684\u77e9\u5f62\u590d\u5236\u50cf\u7d20\u6570\u636e\u3002<\/td><\/tr>
putImageData()<\/a><\/td>\u628a\u56fe\u50cf\u6570\u636e\uff08\u4ece\u6307\u5b9a\u7684 ImageData \u5bf9\u8c61\uff09\u653e\u56de\u753b\u5e03\u4e0a\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n

\u56fe\u50cf\u7ed8\u5236<\/h3>\n\n\n\n
\u65b9\u6cd5<\/th>\u63cf\u8ff0<\/th><\/tr>
drawImage()<\/a><\/td>\u5411\u753b\u5e03\u4e0a\u7ed8\u5236\u56fe\u50cf\u3001\u753b\u5e03\u6216\u89c6\u9891\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n

\u5408\u6210<\/h3>\n\n\n\n
\u5c5e\u6027<\/th>\u63cf\u8ff0<\/th><\/tr>
globalAlpha<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u7ed8\u56fe\u7684\u5f53\u524d alpha \u6216\u900f\u660e\u503c\u3002<\/td><\/tr>
globalCompositeOperation<\/a><\/td>\u8bbe\u7f6e\u6216\u8fd4\u56de\u65b0\u56fe\u50cf\u5982\u4f55\u7ed8\u5236\u5230\u5df2\u6709\u7684\u56fe\u50cf\u4e0a\u3002<\/td><\/tr><\/tbody><\/table>\n\n\n\n

4.\u5176\u4ed6<\/h2>\n\n\n\n

\u5176\u4ed6<\/h3>\n\n\n\n
\u65b9\u6cd5<\/th>\u63cf\u8ff0<\/th><\/tr>
save()<\/td>\u4fdd\u5b58\u5f53\u524d\u73af\u5883\u7684\u72b6\u6001\u3002<\/td><\/tr>
restore()<\/td>\u8fd4\u56de\u4e4b\u524d\u4fdd\u5b58\u8fc7\u7684\u8def\u5f84\u72b6\u6001\u548c\u5c5e\u6027\u3002<\/td><\/tr>
createEvent()<\/td><\/tr>
getContext()<\/td><\/tr>
toDataURL()<\/td><\/tr><\/tbody><\/table>\n\n\n\n

<\/p>\n\n\n\n

\u672c\u6587\u53c2\u8003\u83dc\u9e1f\u6559\u7a0b\u7684H5 canvas\u6559\u7a0b\u3002<\/p>

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