{"id":80,"date":"2009-04-01T14:44:16","date_gmt":"2009-04-01T06:44:16","guid":{"rendered":"http:\/\/leegorous.net\/?p=80"},"modified":"2012-03-04T00:50:12","modified_gmt":"2012-03-03T16:50:12","slug":"arc-in-canvas","status":"publish","type":"post","link":"http:\/\/leegorous.net\/blog\/2009\/04\/01\/arc-in-canvas\/","title":{"rendered":"\u7ed8\u5236\u5f27\u7ebf"},"content":{"rendered":"<p>\u5728 canvas \u91cc\u7ed8\u5236\u5f27\u7ebf\u4e5f\u662f\u975e\u5e38\u7b80\u5355\u7684\u3002<\/p>\n<pre name=\"code\" class=\"brush: js\">\r\narc(x, y, radius, startAngle, endAngle, anticlockwise)\r\n<\/pre>\n<p>x, y \u662f\u5706\u5fc3\u5750\u6807\uff0cradius \u662f\u5706\u5f27\u7684\u534a\u5f84\uff0cstartAngle\uff0cendAngle\u5206\u522b\u662f\u5f27\u7ebf\u8d77\u70b9\u548c\u7ec8\u70b9\u7684\u5f27\u5ea6\uff0c\u6ce8\u610f\uff0c\u662f\u5f27\u5ea6\uff0c\u800c\u4e0d\u662f\u5ea6\uff0c\u5b83\u4eec\u4e4b\u95f4\u53ef\u4ee5\u901a\u8fc7<\/p>\n<pre name=\"code\" class=\"brush: js\">\r\nfunction radian(degrees) {\r\n\treturn (Math.PI\/180)*degrees\r\n}\r\n<\/pre>\n<p>\u6765\u8fdb\u884c\u8f6c\u6362\u3002\u6700\u540e anticlockwise \u7528\u4e8e\u6307\u793a\u5f27\u7ebf\u7ed8\u5236\u7684\u65b9\u5411\uff0ctrue \u65f6\u8868\u793a\u9006\u65f6\u9488\u65b9\u5411\u3002<\/p>\n<pre name=\"code\" class=\"brush: js\">\r\nvar canvas = document.getElementById(&#039;myCanvas&#039;);\r\nvar size = 220;\r\ncanvas.width = canvas.height = size;\r\n\r\nif (canvas.getContext) {\r\n\tvar ctx = canvas.getContext(&#039;2d&#039;);\r\n\tvar X = size\/2;\r\n\tvar Y = size\/2;\r\n\tvar N = 12;\r\n\tvar R = 80;\r\n\tfor (var i=1; i&lt;=12; i++) {\r\n\t\tvar r = 20;\r\n\t\tvar startAngle = 0 - Math.PI\/2;\r\n\t\tvar endAngle   = radian(360*(i\/N)) - Math.PI\/2;\r\n\t\tvar x = X + R*Math.cos(endAngle);\r\n\t\tvar y = Y + R*Math.sin(endAngle);\r\n\t\tvar anticlockwise = false;\r\n\t\t\r\n\t\tctx.beginPath();\r\n\t\tctx.arc(x, y, r, startAngle, endAngle, anticlockwise);\r\n\t\tMath.cos(endAngle + Math.PI\/2) &gt; 0 ? ctx.stroke(): ctx.fill();\r\n\t}\r\n}\r\n<\/pre>\n<p><figure style=\"width: 220px\" class=\"wp-caption alignright\"><img loading=\"lazy\" title=\"Arc\" src=\"http:\/\/farm4.static.flickr.com\/3573\/3403143261_a1dd091a6b_o_d.png\" alt=\"Arc\" width=\"220\" height=\"220\" \/><figcaption class=\"wp-caption-text\">Arc<\/figcaption><\/figure><br \/>\n\u8fd9\u6837\u4e00\u4e2a\u6309\u987a\u65f6\u9488\u53d8\u5316\u7684\u5927\u5706\u5c31\u5b8c\u6210\u4e86\u3002<\/p>\n<p>\u5b8c\u6210\u4e0a\u9762\u7684\u4f8b\u5b50\u5927\u6982\u9700\u8981\u4e00\u70b9\u57fa\u7840\u6570\u5b66\u77e5\u8bc6\u3002<\/p>\n<p>\u53ef\u4ee5\u968f\u610f\u6539\u53d8\u91cc\u9762\u7684\u5706\u7684\u534a\u5f84\u548c\u8d77\u59cb\u3001\u7ed3\u675f\u5f27\u5ea6\u53c8\u6216\u8005\u6700\u540e\u7684\u63a7\u5236\u586b\u5145\u4e0e\u63cf\u8fb9\u7684\u7b97\u5f0f\u6765\u611f\u53d7\u4e00\u4e0b\u90a3\u79cd\u53d8\u5316\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5728 canvas \u91cc\u7ed8\u5236\u5f27\u7ebf\u4e5f\u662f\u975e\u5e38\u7b80\u5355\u7684\u3002 arc(x, y, radius, startAngle, en &hellip; <\/p>\n<p class=\"link-more\"><a href=\"http:\/\/leegorous.net\/blog\/2009\/04\/01\/arc-in-canvas\/\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">\u201c\u7ed8\u5236\u5f27\u7ebf\u201d<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3],"tags":[5,9],"_links":{"self":[{"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/posts\/80"}],"collection":[{"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/comments?post=80"}],"version-history":[{"count":2,"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/posts\/80\/revisions"}],"predecessor-version":[{"id":1082,"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/posts\/80\/revisions\/1082"}],"wp:attachment":[{"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/media?parent=80"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/categories?post=80"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/leegorous.net\/blog\/wp-json\/wp\/v2\/tags?post=80"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}