{"id":6747,"date":"2020-07-29T21:34:57","date_gmt":"2020-07-29T13:34:57","guid":{"rendered":"http:\/\/leybreeze.com\/blog\/?p=6747"},"modified":"2020-07-29T21:34:57","modified_gmt":"2020-07-29T13:34:57","slug":"%e8%a7%a3%e5%86%b3-html-canvas-%e5%85%83%e7%b4%a0%e5%9c%a8%e9%ab%98%e5%83%8f%e7%b4%a0%e5%af%86%e5%ba%a6-%e9%ab%98%e5%88%86%e8%be%a8%e7%8e%87%e5%b1%8f%e5%b9%95%e4%b8%8a%e6%98%be%e7%a4%ba%e6%a8%a1","status":"publish","type":"post","link":"http:\/\/leybreeze.com\/blog\/?p=6747","title":{"rendered":"\u89e3\u51b3 HTML Canvas \u5143\u7d20\u5728\u9ad8\u50cf\u7d20\u5bc6\u5ea6\/\u9ad8\u5206\u8fa8\u7387\u5c4f\u5e55\u4e0a\u663e\u793a\u6a21\u7cca\u7684\u95ee\u9898"},"content":{"rendered":"\n<p>\u6700\u8fd1\u5728\u4f7f\u7528 HTML Canvas \u5143\u7d20\u65f6\u53d1\u73b0\u901a\u8fc7 fillText() \u7ed8\u5236\u7684\u6587\u5b57\u660e\u663e\u53d1\u865a\uff0c\u50cf\u662f\u4ee5\u4f4e\u5206\u8fa8\u7387\u6e32\u67d3\u540e\u653e\u5927\u6240\u81f4\uff0c\u518d\u4ed4\u7ec6\u4e00\u68c0\u67e5\uff0c\u53d1\u73b0\u4e8b\u5b9e\u4e0a\u5305\u62ec fillRect() \u5728\u5185\u7684\u5176\u4ed6\u56fe\u6848\u4e5f\u90fd\u5b58\u5728\u76f8\u540c\u7684\u95ee\u9898\u3002<\/p>\n\n\n\n<p>\u521d\u6b65\u63a8\u6d4b\u548c\u663e\u793a\u8bbe\u5907\u4f7f\u7528\u4e86\u8f83\u9ad8\u7684 DPI \u6709\u5173\uff0c\u968f\u8fdb\u884c\u4e86\u4e00\u756a\u641c\u7d22\uff0c\u5728 Stackoverflow \u3001Medium \u7b49\u7ad9\u70b9\u90fd\u6709\u4e00\u4e9b\u63d0\u95ee\u548c\u56de\u7b54\u3002\u7136\u800c\u610f\u5916\u7684\u662f\uff0c\u81ea\u5df1\u80fd\u627e\u5230\u7684\u4e00\u4e9b\u89e3\u7b54\uff0c\u81f3\u5c11\u5728\u81ea\u5df1\u8fd9\u8fb9\u5e76\u4e0d\u80fd\u89e3\u51b3\u95ee\u9898\u3002<\/p>\n\n\n\n<p>\u7ecf\u8fc7\u6478\u7d22\uff0c\u627e\u5230\u4e86\u80fd\u591f\u89e3\u51b3\u81ea\u5df1\u95ee\u9898\u7684\u529e\u6cd5\uff0c\u5206\u4eab\u4e8e\u6b64\uff0c\u4ee5\u4fbf\u540e\u4eba\u3002<\/p>\n\n\n\n<p>\u4ee5\u4e0b\u4e3a Angular component \u4ee3\u7801\u7247\u6bb5\uff0c\u8bed\u8a00\u4e3a TypeScript\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">@ViewChild('canvas', { static: true }) canvas: ElementRef; \/\/ Canvas \u5143\u7d20\n@ViewChild('canvasDiv', { static: true }) canvasDiv: ElementRef; \/\/ Canvas \u5143\u7d20\u7684\u7236\u5143\u7d20\uff0c\u4e00\u4e2a div\nprivate ctx: CanvasRenderingContext2D; \/\/ Canvas context\n\nprivate dpiRatio: number; \/\/ DPI \u7f29\u653e\u6bd4\u4f8b\nprivate canvasDivWidth: number;  \/\/ \u7236\u5143\u7d20\u5bbd\u5ea6<\/pre>\n\n\n\n<p>&#8230;&#8230;<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">this.dpiRatio = window.devicePixelRatio;\n\nthis.canvasDivWidth\u00a0=\u00a0this.canvasDiv.nativeElement.offsetWidth;\n\n\/\/ \u5206\u522b\u8bbe\u7f6e canvas \u7684\u5bbd\u5ea6\u548c\u6837\u5f0f\u5bbd\u5ea6\uff0ccanvas \u7684\u663e\u793a\u5c3a\u5bf8\u5c06\u4f1a\u51cf\u534a\nthis.ctx = this.canvas.nativeElement.getContext('2d');\nthis.ctx.canvas.width = this.canvasWidth * this.dpiRatio;\nthis.ctx.canvas.style.width = this.canvasWidth + 'px';\n\n\/\/ \u5728\u7ed8\u5236\u65f6\u8003\u8651\u7f29\u653e\u56e0\u7d20\nthis.ctx.font\u00a0=\u00a012\u00a0*\u00a0this.dpiRatio\u00a0+\u00a0'px\u00a0Roboto';\nthis.ctx.fillText('HIDPI\u6587\u5b57',\u00a0x \u00a0*\u00a0this.dpiRatio,\u00a0y\u00a0*\u00a0this.dpiRatio);<\/pre>\n\n\n\n<p>\u4e00\u4e2a\u60ac\u800c\u672a\u51b3\u7684\u95ee\u9898\u662f\uff0ccanvas context \u672c\u8eab\u7684 transfer \u51fd\u6570\u4f3c\u4e4e\u4e0d\u80fd\u505a\u5230\u6574\u4f53\u7684\u653e\u5927\uff0c\u56e0\u6b64\u8fd9\u91cc\u4f5c\u4e3a\u4e34\u65f6\u65b9\u6848\u6682\u65f6\u5728\u7ed8\u5236\u6bcf\u4e00\u4e2a\u56fe\u5f62\u65f6\u90fd\u4e58\u4ee5\u4e86\u7f29\u653e\u500d\u7387\u3002\u8fd9\u91cc\u5e94\u8be5\u6709\u66f4\u597d\u7684\u529e\u6cd5\uff0c\u4e0d\u8fc7\u9650\u4e8e\u65f6\u95f4\uff0c\u6682\u4e14\u6401\u7f6e\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6700\u8fd1\u5728\u4f7f\u7528 HTML Canvas \u5143\u7d20\u65f6\u53d1\u73b0\u901a\u8fc7 fillText() \u7ed8\u5236\u7684\u6587\u5b57\u660e\u663e\u53d1\u865a\uff0c\u50cf\u662f\u4ee5\u4f4e\u5206\u8fa8\u7387\u6e32 &hellip; <a href=\"http:\/\/leybreeze.com\/blog\/?p=6747\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">\u201c\u89e3\u51b3 HTML Canvas \u5143\u7d20\u5728\u9ad8\u50cf\u7d20\u5bc6\u5ea6\/\u9ad8\u5206\u8fa8\u7387\u5c4f\u5e55\u4e0a\u663e\u793a\u6a21\u7cca\u7684\u95ee\u9898\u201d<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[145],"tags":[159,122],"_links":{"self":[{"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6747"}],"collection":[{"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6747"}],"version-history":[{"count":1,"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6747\/revisions"}],"predecessor-version":[{"id":6758,"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/6747\/revisions\/6758"}],"wp:attachment":[{"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6747"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6747"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/leybreeze.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6747"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}