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Canvas Drawing Features

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The basic process of JS drawing is as follows:

    1. JS through the ID to find the canvas element, the following code:
      var c=document.getElementById(‘myCanvas‘)
    2. Create a context object with the following code:
      var cxt=c.getContext(‘2d‘)
      2d is the only function parameter that might support 3D drawings in the future, and all the drawing work is done on the context object.

Canvas drawing-related objects

    1. Cxt.beginpath () Start drawing path
    2. Cxt.closepath () End drawing path
    3. Cxt.stroke () a real drawing
    4. Cxt.strokestyle= ' #fff ', set border color
    5. cxt.linewidth=2, setting the border size
    6. cxt.fillstyle= ' Red ' to set the content fill area color
    7. Cxt.arc (X,y,radius,startangle,endangle,true/false), draw a circular path with parameters of center coordinates (x, y), start and end angles, clockwise/counterclockwise
    8. Cxt.strokerect (X,y,width,height), drawing a rectangular path
    9. Cxt.fillrect (X,y,width,height), drawing a rectangular shape
    10. Cxt.createradialgradient (xstart,ystart,radiusstart,xend,yend,radiusend), Radial gradient range settings
    11. Cxt.createlineargradient (xstart,ystart,xend,yend), linear gradient range settings

HTML code:

<body>    <p>        <span onclick="Btn1_click ();" onmouseover="this.style.cursor= ' pointer ';" >Solid Circle</span>        <span onclick="Btn2_click ();" onmouseover="this.style.cursor= ' pointer ';" >Border Circle</span>        <span onclick="Btn3_click ();" onmouseover="this.style.cursor= ' pointer ';" >Connecting Circle</span>        <span onclick="Btn4_click ();" onmouseover="this.style.cursor= ' pointer ';" >Gradient Circle</span>    </P>    <canvas id="MyCanvas" width= "400px" height=" 400px "></Canvas></body>

JS Code:

<script type="Text/javascript">     function $(ID) {        returndocument.getElementById (ID); } function btn1_click(){        varcvs=$ (' MyCanvas ');varCxt=cvs.getcontext (' 2d '); Cxt.clearrect (0,0, -, -);        Cxt.beginpath (); Cxt.arc ( -, -, -,0,Math. pi*2,true);        Cxt.closepath (); cxt.fillstyle=' #eee ';    Cxt.fill (); } function btn2_click(){        varcvs=$ (' MyCanvas ');varCxt=cvs.getcontext (' 2d '); Cxt.clearrect (0,0, -, -);        Cxt.beginpath (); Cxt.arc ( -, -, -,0,Math. pi*2,true);        Cxt.closepath (); cxt.strokestyle=' #666 '; Cxt.linewidth=2;    Cxt.stroke (); } function btn3_click(){        varcvs=$ (' MyCanvas ');varCxt=cvs.getcontext (' 2d '); Cxt.clearrect (0,0, -, -);        Cxt.beginpath (); Cxt.arc ( -, -, -,0,Math. pi*2,true);        Cxt.closepath (); cxt.strokestyle=' #666 '; Cxt.linewidth=2; cxt.fillstyle=' #eee ';        Cxt.fill ();        Cxt.stroke ();        Cxt.beginpath (); Cxt.arc ( the, -, -,0,Math. pi*2,true);        Cxt.closepath (); cxt.strokestyle=' #666 '; Cxt.linewidth=2;    Cxt.stroke (); } function btn4_click(){        varcvs=$ (' MyCanvas ');varCxt=cvs.getcontext (' 2d '); Cxt.clearrect (0,0, -, -);        Cxt.beginpath (); Cxt.arc ( -, -, -,0,Math. pi*2,true);        Cxt.closepath (); cxt.strokestyle=' #666 '; Cxt.linewidth=2;varGnt=cxt.createradialgradient ( -, -,0, -, -, -); Gnt.addcolorstop (0,' #f00 '); Gnt.addcolorstop (0.3,' #0f0 '); Gnt.addcolorstop (1,' #00f ');        Cxt.fillstyle=gnt;    Cxt.fill (); }</script>

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Canvas Drawing Features

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