createPattern method

發行項
05/02/2017

Returns a CanvasPattern object that repeats the specified element in the specified direction.

Syntax

CanvasPattern retVal = object.createPattern(image, repetition);

Parameters

image [in]

Type: IDispatch

An image, canvas, or video element of the pattern to use.

repetition [in]

Type: number

The direction of repetition. This parameter specifies one of the following values:

repeat

The pattern repeats in both horizontal and vertical directions.

repeat-x

The pattern repeats only in the horizontal direction.

repeat-y

The pattern repeats only lin the vertical direction.

no-repeat

The pattern prints only once and does not repeat.

Standards information

HTML Canvas 2D Context, Section 5

Remarks

If the repetition parameter equals NULL or an empty string, the ICanvasRenderingContext2D::createPattern method assumes that the repetition parameter is repeat.

Examples

This example shows the same effect but uses video for the pattern. The video pattern works best when the video size is small. The width of the canvas is set to 2000 x 2000 pixels. However, you can automatically scale it to the IHTMLWindow7::innerWidth of the browser window by un-commenting two lines. If you use the IHTMLWindow7::innerWidth, when you expand your window, be sure to refresh the example. See the sample in action. The Creating a video fill pattern in canvas blog post describes the example more fully.

<!DOCTYPE html> 
<html>
  <head>
    <title>Video pattern example</title>   
    <!-- only force Internet Explorer standards mode for testing on local or intranet machine -->
    <!-- <meta http-equiv="X-UA-Compatible" content="IE=edge" /> -->
    <style>
      button {
      width:150px;
      }

    </style>
  </head>
  <body>

    <table>
      <tr>
        <td> 
          <div>
            <h1>Canvas Patterns with Video</h1>
            <h3>Make your page full screen, and click the buttons to change the view</h3>
            <button onclick="draw('repeat')">Repeat all</button>
            <button onclick="draw('repeat-x')">Repeat across</button> 
            <button onclick="draw('repeat-y')">Repeat down</button>
            <button onclick="draw('no-repeat')">No Repeat</button><br />     
            <label>Enter a video URL: <input type="text" id="videoSrc" size="80" value="http://ie.microsoft.com/testdrive/ieblog/2011/nov/pp4_blog_demo.mp4" /></label> <br />
          </div>
        </td>
        <td>  
          <video id="pix" controls autoplay width="300">
            This browser or document mode doesn't support video
          </video><br />
        </td>
      </tr>
    </table>   
    <canvas id="MyCanvas" width="2000" height="2000">This browser or document mode doesn't support canvas</canvas>
    <script >
      // Some global variables    
      var canvas = document.getElementById("MyCanvas");
      var lastDirection;
      var timerID;
      var pattern;
      var lastSrc;
      var video = document.getElementById("pix"); // Get the video object.
      //  Check for canvas, and get context
      if (canvas.getContext) {
        var ctx = canvas.getContext("2d");  // Get the context.
        //  Optionally set based on window width/height
   //     canvas.width = window.innerWidth;  // Set canvas width and height
   //     canvas.height = window.innerHeight;
        var w = canvas.width;  // Set up w and h for loop below.              
        var h = canvas.height;
      }

      function draw(direction) {
        if (ctx) {
          var src = document.getElementById("videoSrc").value;
          if (src == "") {
            return false;
          }

          if (lastSrc != src) {   // Change of video
            video.src = src;    // Assign the video src
            lastSrc = src;      // Reassign lastSrc          
            video.load();       // Load src into video control
            video.play();       // Play it
          }

          // Clear the screen every time a new direction is selected.
          if (lastDirection != direction) {  // Check if direction has changed
            window.cancelAnimationFrame(timerID);
            ctx.clearRect(0, 0, canvas.width, canvas.height);    // Clear the last image.
            lastDirection = direction;  // Reset the direction flag
          }
          draw2();
        }
      }

      function draw2() {
        if (video.paused || video.ended) {
          return false;
        } // Stop loop when video ends
        pattern = ctx.createPattern(video, lastDirection); // Get the video frame   
        ctx.fillStyle = pattern;  // Assign pattern as a fill style. 
        ctx.fillRect(0, 0, w, h); // Fill the canvas. 
        timerID = window.requestAnimationFrame(draw2);
      }
      draw("repeat");   // Start video when loaded
    </script>
  </body>
</html>

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