{"id":120,"date":"2019-06-30T16:10:22","date_gmt":"2019-06-30T08:10:22","guid":{"rendered":"http:\/\/admin.evshou.com\/?p=120"},"modified":"2020-09-22T09:42:07","modified_gmt":"2020-09-22T01:42:07","slug":"html5-canvas","status":"publish","type":"post","link":"https:\/\/www.9713job.com\/?p=120","title":{"rendered":"HTML5 Canvas"},"content":{"rendered":"\n

<canvas>\u5143\u7d20\u662fHTML5\u4e2d\u7684\u65b0\u5143\u7d20\uff0c\u901a\u8fc7\u4f7f\u7528\u8be5\u5143\u7d20\uff0c\u4f60\u53ef\u4ee5\u5728\u7f51\u9875\u4e2d\u7ed8\u5236\u6240\u9700\u7684\u56fe\u5f62\u3002
<\/p>\n\n\n\n

\u4ec0\u4e48\u662f Canvas?<\/h2>\n\n\n\n

HTML5 \u5143\u7d20\u7528\u4e8e\u56fe\u5f62\u7684\u7ed8\u5236\uff0c\u901a\u8fc7\u811a\u672c (\u901a\u5e38\u662fJavaScript)\u6765\u5b8c\u6210.<\/p>\n\n\n\n

\u6807\u7b7e\u53ea\u662f\u56fe\u5f62\u5bb9\u5668\uff0c\u60a8\u5fc5\u987b\u4f7f\u7528\u811a\u672c\u6765\u7ed8\u5236\u56fe\u5f62\u3002<\/p>\n\n\n\n

\u4f60\u53ef\u4ee5\u901a\u8fc7\u591a\u79cd\u65b9\u6cd5\u4f7f\u7528Canva\u7ed8\u5236\u8def\u5f84,\u76d2\u3001\u5706\u3001\u5b57\u7b26\u4ee5\u53ca\u6dfb\u52a0\u56fe\u50cf\u3002<\/p>\n\n\n\n\n\n\n\n

\u521b\u5efa\u4e00\u4e2a\u753b\u5e03\uff08Canvas\uff09<\/h2>\n\n\n\n

\u4e00\u4e2a\u753b\u5e03\u5728\u7f51\u9875\u4e2d\u662f\u4e00\u4e2a\u77e9\u5f62\u6846\uff0c\u901a\u8fc7 <canvas> \u5143\u7d20\u6765\u7ed8\u5236.<\/p>\n\n\n\n

\u6ce8\u610f: \u9ed8\u8ba4\u60c5\u51b5\u4e0b <canvas> \u5143\u7d20\u6ca1\u6709\u8fb9\u6846\u548c\u5185\u5bb9\u3002<\/p>\n\n\n\n

<canvas>\u7b80\u5355\u5b9e\u4f8b\u5982\u4e0b:
<canvas id=”myCanvas” width=”200″ height=”100″><\/canvas> <\/p>\n\n\n\n

\u6ce8\u610f:<\/strong> \u6807\u7b7e\u901a\u5e38\u9700\u8981\u6307\u5b9a\u4e00\u4e2aid\u5c5e\u6027 (\u811a\u672c\u4e2d\u7ecf\u5e38\u5f15\u7528), width \u548c height \u5c5e\u6027\u5b9a\u4e49\u7684\u753b\u5e03\u7684\u5927\u5c0f\u3002<\/p>\n\n\n\n

\u63d0\u793a:<\/strong> \u4f60\u53ef\u4ee5\u5728HTML\u9875\u9762\u4e2d\u4f7f\u7528\u591a\u4e2a <canvas> \u5143\u7d20.<\/p>\n\n\n\n

\u4f7f\u7528 style \u5c5e\u6027\u6765\u6dfb\u52a0\u8fb9\u6846:
<canvas id=”myCanvas” width=”200″ height=”100″ style=”border:10px dotted #000000; background:#ddd;”>
\u60a8\u7684\u6d4f\u89c8\u5668\u4e0d\u652f\u6301 HTML5 canvas \u6807\u7b7e\u3002
<\/canvas><\/p>\n\n\n\n

\n\n\n\n

\u4f7f\u7528 JavaScript \u6765\u7ed8\u5236\u56fe\u50cf<\/h2>\n\n\n\n

canvas \u5143\u7d20\u672c\u8eab\u662f\u6ca1\u6709\u7ed8\u56fe\u80fd\u529b\u7684\u3002\u6240\u6709\u7684\u7ed8\u5236\u5de5\u4f5c\u5fc5\u987b\u5728 JavaScript \u5185\u90e8\u5b8c\u6210\uff1a
<canvas id=”myCanvas” width=”200″ height=”100″ style=”border:1px solid #c3c3c3;”> \u60a8\u7684\u6d4f\u89c8\u5668\u4e0d\u652f\u6301 HTML5 canvas \u6807\u7b7e\u3002<\/canvas>
js:
var c=document.getElementById(“myCanvas”);
var ctx=c.getContext(“2d”);
ctx.fillStyle=”#FF0000″;
ctx.fillRect(0,0,150,75);<\/p>\n\n\n\n

\u5b9e\u4f8b\u89e3\u6790:<\/strong><\/p>\n\n\n\n

\u9996\u5148\uff0c\u627e\u5230 <canvas> \u5143\u7d20:
var c=document.getElementById(“myCanvas”);
\u7136\u540e\uff0c\u521b\u5efa context \u5bf9\u8c61\uff1a
var ctx=c.getContext(“2d”);
getContext(“2d”) \u5bf9\u8c61\u662f\u5185\u5efa\u7684 HTML5 \u5bf9\u8c61\uff0c\u62e5\u6709\u591a\u79cd\u7ed8\u5236\u8def\u5f84\u3001\u77e9\u5f62\u3001\u5706\u5f62\u3001\u5b57\u7b26\u4ee5\u53ca\u6dfb\u52a0\u56fe\u50cf\u7684\u65b9\u6cd5\u3002
\u4e0b\u9762\u7684\u4e24\u884c\u4ee3\u7801\u7ed8\u5236\u4e00\u4e2a\u7ea2\u8272\u7684\u77e9\u5f62\uff1a
ctx.fillStyle=”#FF0000″;
ctx.fillRect(0,0,150,75);
\u8bbe\u7f6efillStyle\u5c5e\u6027\u53ef\u4ee5\u662fCSS\u989c\u8272\uff0c\u6e10\u53d8\uff0c\u6216\u56fe\u6848\u3002fillStyle\u9ed8\u8ba4\u8bbe\u7f6e\u662f#000000\uff08\u9ed1\u8272\uff09\u3002
fillRect(x,y,width,height<\/em>) \u65b9\u6cd5\u5b9a\u4e49\u4e86\u77e9\u5f62\u5f53\u524d\u7684\u586b\u5145\u65b9\u5f0f\u3002<\/p>\n\n\n\n

\n\n\n\n

Canvas \u5750\u6807<\/h2>\n\n\n\n

canvas \u662f\u4e00\u4e2a\u4e8c\u7ef4\u7f51\u683c\u3002
canvas \u7684\u5de6\u4e0a\u89d2\u5750\u6807\u4e3a (0,0)
\u4e0a\u9762\u7684 fillRect \u65b9\u6cd5\u62e5\u6709\u53c2\u6570 (0,0,150,75)\u3002
\u610f\u601d\u662f\uff1a\u5728\u753b\u5e03\u4e0a\u7ed8\u5236 150×75 \u7684\u77e9\u5f62\uff0c\u4ece\u5de6\u4e0a\u89d2\u5f00\u59cb (0,0)\u3002
\u5750\u6807\u5b9e\u4f8b<\/strong>
\u5982\u4e0b\u56fe\u6240\u793a\uff0c\u753b\u5e03\u7684 X \u548c Y \u5750\u6807\u7528\u4e8e\u5728\u753b\u5e03\u4e0a\u5bf9\u7ed8\u753b\u8fdb\u884c\u5b9a\u4f4d\u3002<\/p>\n\n\n\n

\n\n\n\n

Canvas – \u8def\u5f84<\/h2>\n\n\n\n

\u5728Canvas\u4e0a\u753b\u7ebf\uff0c\u6211\u4eec\u5c06\u4f7f\u7528\u4ee5\u4e0b\u4e24\u79cd\u65b9\u6cd5\uff1a<\/p>\n\n\n\n

  • moveTo(x,y<\/em>) \u5b9a\u4e49\u7ebf\u6761\u5f00\u59cb\u5750\u6807<\/li>
  • lineTo(x,y<\/em>) \u5b9a\u4e49\u7ebf\u6761\u7ed3\u675f\u5750\u6807<\/li><\/ul>\n\n\n\n

    \u7ed8\u5236\u7ebf\u6761\u6211\u4eec\u5fc5\u987b\u4f7f\u7528\u5230 “ink” \u7684\u65b9\u6cd5\uff0c\u5c31\u50cfstroke().<\/p>\n\n\n\n

    \u5b9e\u4f8b<\/h2>\n\n\n\n

    \u5b9a\u4e49\u5f00\u59cb\u5750\u6807(0,0), \u548c\u7ed3\u675f\u5750\u6807 (200,100). \u7136\u540e\u4f7f\u7528 stroke() \u65b9\u6cd5\u6765\u7ed8\u5236\u7ebf\u6761:<\/p>\n\n\n\n

    \"\"\/<\/figure>\n\n\n\n

    JavaScript:
    var c=document.getElementById(“myCanvas”);\u00a0
    var ctx=c.getContext(“2d”);\u00a0
    ctx.moveTo(0,0);\u00a0
    ctx.lineTo(200,100);\u00a0
    ctx.stroke(); <\/p>\n\n\n\n

    \u5728canvas\u4e2d\u7ed8\u5236\u5706\u5f62, \u6211\u4eec\u5c06\u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5:<\/p>\n\n\n\n

    • arc(x,y,r,start,stop)<\/li><\/ul>\n\n\n\n

      \u5b9e\u9645\u4e0a\u6211\u4eec\u5728\u7ed8\u5236\u5706\u5f62\u65f6\u4f7f\u7528\u4e86 “ink” \u7684\u65b9\u6cd5, \u6bd4\u5982 stroke() \u6216\u8005 fill().<\/p>\n\n\n\n

      \u5b9e\u4f8b<\/h2>\n\n\n\n

      \u4f7f\u7528 arc() \u65b9\u6cd5 \u7ed8\u5236\u4e00\u4e2a\u5706:<\/p>\n\n\n\n

      \"\"\/<\/figure>\n\n\n\n

      JavaScript:
      var c=document.getElementById(“myCanvas”);\u00a0
      var ctx=c.getContext(“2d”);\u00a0
      ctx.beginPath();\u00a0
      ctx.arc(95,50,40,0,2*Math.PI);\u00a0
      ctx.stroke(); <\/p>\n\n\n\n

      \n\n\n\n

      Canvas – \u6587\u672c<\/h2>\n\n\n\n

      \u4f7f\u7528 canvas \u7ed8\u5236\u6587\u672c\uff0c\u91cd\u8981\u7684\u5c5e\u6027\u548c\u65b9\u6cd5\u5982\u4e0b\uff1a<\/p>\n\n\n\n

      • font – \u5b9a\u4e49\u5b57\u4f53<\/li>
      • fillText(text,x,y<\/em>) – \u5728 canvas \u4e0a\u7ed8\u5236\u5b9e\u5fc3\u7684\u6587\u672c<\/li>
      • strokeText(text,x,y<\/em>) – \u5728 canvas \u4e0a\u7ed8\u5236\u7a7a\u5fc3\u7684\u6587\u672c<\/li><\/ul>\n\n\n\n

        \u4f7f\u7528 fillText():<\/p>\n\n\n\n

        \u5b9e\u4f8b<\/h2>\n\n\n\n

        \u4f7f\u7528 “Arial” \u5b57\u4f53\u5728\u753b\u5e03\u4e0a\u7ed8\u5236\u4e00\u4e2a\u9ad8 30px \u7684\u6587\u5b57\uff08\u5b9e\u5fc3\uff09\uff1a<\/p>\n\n\n\n

        \"\"\/<\/figure>\n\n\n\n

        JavaScript:
        var c=document.getElementById(“myCanvas”);\u00a0
        var ctx=c.getContext(“2d”);\u00a0
        ctx.font=”30px Arial”;\u00a0
        ctx.fillText(“Hello World”,10,50); <\/p>\n\n\n\n

        \u4f7f\u7528 strokeText(): <\/p>\n\n\n\n

        \u5b9e\u4f8b<\/h2>\n\n\n\n

        \u4f7f\u7528 “Arial” \u5b57\u4f53\u5728\u753b\u5e03\u4e0a\u7ed8\u5236\u4e00\u4e2a\u9ad8 30px \u7684\u6587\u5b57\uff08\u7a7a\u5fc3\uff09\uff1a<\/p>\n\n\n\n

        \"\"\/<\/figure>\n\n\n\n

        JavaScript:<\/p>\n\n\n\n

        var c=document.getElementById(“myCanvas”);\u00a0
        var ctx=c.getContext(“2d”);\u00a0
        ctx.font=”30px Arial”;\u00a0
        ctx.strokeText(“Hello World”,10,50);<\/p>\n\n\n\n

        \n\n\n\n

        Canvas –  \u6e10\u53d8<\/h2>\n\n\n\n

        \u6e10\u53d8\u53ef\u4ee5\u586b\u5145\u5728\u77e9\u5f62, \u5706\u5f62, \u7ebf\u6761, \u6587\u672c\u7b49\u7b49, \u5404\u79cd\u5f62\u72b6\u53ef\u4ee5\u81ea\u5df1\u5b9a\u4e49\u4e0d\u540c\u7684\u989c\u8272\u3002<\/p>\n\n\n\n

        \u4ee5\u4e0b\u6709\u4e24\u79cd\u4e0d\u540c\u7684\u65b9\u5f0f\u6765\u8bbe\u7f6eCanvas\u6e10\u53d8\uff1a<\/p>\n\n\n\n

        • createLinearGradient(x,y,x1,y1<\/em>) – \u521b\u5efa\u7ebf\u6761\u6e10\u53d8<\/li>
        • createRadialGradient(x,y,r,x1,y1,r1<\/em>) – \u521b\u5efa\u4e00\u4e2a\u5f84\u5411\/\u5706\u6e10\u53d8<\/li><\/ul>\n\n\n\n

          \u5f53\u6211\u4eec\u4f7f\u7528\u6e10\u53d8\u5bf9\u8c61\uff0c\u5fc5\u987b\u4f7f\u7528\u4e24\u79cd\u6216\u4e24\u79cd\u4ee5\u4e0a\u7684\u505c\u6b62\u989c\u8272\u3002<\/p>\n\n\n\n

          addColorStop()\u65b9\u6cd5\u6307\u5b9a\u989c\u8272\u505c\u6b62\uff0c\u53c2\u6570\u4f7f\u7528\u5750\u6807\u6765\u63cf\u8ff0\uff0c\u53ef\u4ee5\u662f0\u81f31.<\/p>\n\n\n\n

          \u4f7f\u7528\u6e10\u53d8\uff0c\u8bbe\u7f6efillStyle\u6216strokeStyle\u7684\u503c\u4e3a\u6e10\u53d8\uff0c\u7136\u540e\u7ed8\u5236\u5f62\u72b6\uff0c\u5982\u77e9\u5f62\uff0c\u6587\u672c\uff0c\u6216\u4e00\u6761\u7ebf\u3002<\/p>\n\n\n\n

          \u4f7f\u7528 createLinearGradient():<\/p>\n\n\n\n

          \u5b9e\u4f8b<\/h2>\n\n\n\n

          \u521b\u5efa\u4e00\u4e2a\u7ebf\u6027\u6e10\u53d8\u3002\u4f7f\u7528\u6e10\u53d8\u586b\u5145\u77e9\u5f62:<\/p>\n\n\n\n

          \"\"\/<\/figure>\n\n\n\n

          JavaScript:
          var c=document.getElementById(“myCanvas”);\u00a0
          var ctx=c.getContext(“2d”);\u00a0
          \/\/ Create gradient\u00a0
          var grd=ctx.createLinearGradient(0,0,200,0);\u00a0
          grd.addColorStop(0,”red”);\u00a0
          grd.addColorStop(1,”white”);\u00a0
          \/\/ Fill with gradient\u00a0
          ctx.fillStyle=grd;\u00a0
          ctx.fillRect(10,10,150,80); <\/p>\n\n\n\n

          \u4f7f\u7528 createRadialGradient(): <\/p>\n\n\n\n

          \u5b9e\u4f8b<\/h2>\n\n\n\n

          \u521b\u5efa\u4e00\u4e2a\u5f84\u5411\/\u5706\u6e10\u53d8\u3002\u4f7f\u7528\u6e10\u53d8\u586b\u5145\u77e9\u5f62\uff1a<\/p>\n\n\n\n

          \"\"\/<\/figure>\n\n\n\n

          JavaScript:
          var c=document.getElementById(“myCanvas”);\u00a0
          var ctx=c.getContext(“2d”);\u00a0
          \/\/ Create gradient\u00a0
          var grd=ctx.createRadialGradient(75,50,5,90,60,100);\u00a0
          grd.addColorStop(0,”red”);\u00a0
          grd.addColorStop(1,”white”);\u00a0
          \/\/ Fill with gradient\u00a0
          ctx.fillStyle=grd;\u00a0
          ctx.fillRect(10,10,150,80); <\/p>\n\n\n\n

          \u63d0\u793a\uff1a<\/strong>\u5f53\u4f7f\u7528<canvas>\u5143\u7d20\u521b\u5efa\u5f84\u5411\u6e10\u53d8\u7684\u65f6\u5019 context.createRadialGradient(x , y , r , x1 , y1 , r1) \u62ec\u53f7\u5185\u7684\u53c2\u6570\u6709\u5982\u4e0b\u7684\u542b\u4e49:<\/p>\n\n\n\n

          •  x\uff1a\u8868\u793a\u6e10\u53d8\u7684\u5f00\u59cb\u5706\u7684 x \u5750\u6807<\/li>
          •  y\uff1a\u8868\u793a\u6e10\u53d8\u7684\u5f00\u59cb\u5706\u7684 y \u5750\u6807<\/li>
          •  r\uff1a\u8868\u793a\u5f00\u59cb\u5706\u7684\u534a\u5f84<\/li>
          •  x1\uff1a\u8868\u793a\u6e10\u53d8\u7684\u7ed3\u675f\u5706\u7684 x \u5750\u6807<\/li>
          •  y1\uff1a\u8868\u793a\u6e10\u53d8\u7684\u7ed3\u675f\u5706\u7684 y \u5750\u6807<\/li>
          •  r1\uff1a\u8868\u793a\u7ed3\u675f\u5706\u7684\u534a\u5f84<\/li><\/ul>\n\n\n\n
            \n\n\n\n

            Canvas – \u56fe\u50cf<\/h2>\n\n\n\n

            \u628a\u4e00\u5e45\u56fe\u50cf\u653e\u7f6e\u5230\u753b\u5e03\u4e0a, \u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5:<\/p>\n\n\n\n

            • drawImage(image,x,y<\/em>)<\/li><\/ul>\n\n\n\n

              \u4f7f\u7528\u56fe\u50cf:<\/h2>\n\n\n\n
              \"The<\/figure>\n\n\n\n

              \u5b9e\u4f8b<\/h2>\n\n\n\n

              \u628a\u4e00\u5e45\u56fe\u50cf\u653e\u7f6e\u5230\u753b\u5e03\u4e0a:<\/p>\n\n\n\n

              \"\"\/<\/figure>\n\n\n\n

              JavaScript:
              var c=document.getElementById(“myCanvas”);\u00a0
              var ctx=c.getContext(“2d”);\u00a0
              var img=document.getElementById(“scream”);\u00a0
              ctx.drawImage(img,10,10); <\/p>\n","protected":false},"excerpt":{"rendered":"

              <canvas>\u5143\u7d20\u662fHTML5\u4e2d\u7684\u65b0\u5143\u7d20\uff0c\u901a\u8fc7\u4f7f\u7528\u8be5\u5143\u7d20\uff0c\u4f60\u53ef\u4ee5\u5728\u7f51\u9875\u4e2d\u7ed8\u5236\u6240\u9700\u7684\u56fe\u5f62\u3002 \u4ec0\u4e48\u662f Ca […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[],"class_list":["post-120","post","type-post","status-publish","format-standard","hentry"],"_links":{"self":[{"href":"https:\/\/www.9713job.com\/index.php?rest_route=\/wp\/v2\/posts\/120","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.9713job.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.9713job.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.9713job.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.9713job.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=120"}],"version-history":[{"count":5,"href":"https:\/\/www.9713job.com\/index.php?rest_route=\/wp\/v2\/posts\/120\/revisions"}],"predecessor-version":[{"id":125,"href":"https:\/\/www.9713job.com\/index.php?rest_route=\/wp\/v2\/posts\/120\/revisions\/125"}],"wp:attachment":[{"href":"https:\/\/www.9713job.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=120"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.9713job.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=120"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.9713job.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=120"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}