js图片旋转

  <script type="text/javascript" language="javascript">

    function rotate(id, angle, whence) {

      var p = document.getElementById(id);

      if (!whence) {

        p.angle = ((p.angle == undefined ? 0 : p.angle) + angle) % 360;

      }

      else {

        p.angle = angle;

      }

      if (p.angle >= 0) {

        var rotation = Math.PI * p.angle / 180;

      }

      else {

        var rotation = Math.PI * (360 + p.angle) / 180;

      }

      var costheta = Math.cos(rotation);

      var sintheta = Math.sin(rotation);

      if (document.all && !window.opera) {

        var canvas = document.createElement(‘img‘);

        canvas.src = p.src;

        canvas.height = p.height;

        canvas.width = p.width;

        canvas.style.filter = "progid:DXImageTransform.Microsoft.Matrix(M11=" + costheta + ",M12=" + (-sintheta) + ",M21=" + sintheta + ",M22=" + costheta + ",SizingMethod=‘auto expand‘)";

      }

      else {

        var canvas = document.createElement(‘canvas‘);

        if (!p.oImage) {

          canvas.oImage = new Image();

          canvas.oImage.src = p.src;

        }

        else {

          canvas.oImage = p.oImage;

        }

        //alert(canvas.width)

        canvas.style.width = canvas.width = Math.abs(costheta * canvas.oImage.width) + Math.abs(sintheta * canvas.oImage.height);

        canvas.style.height = canvas.height = Math.abs(costheta * canvas.oImage.height) + Math.abs(sintheta * canvas.oImage.width);

        var context = canvas.getContext(‘2d‘);

        context.save();

        if (rotation <= Math.PI / 2) {

          context.translate(sintheta * canvas.oImage.height, 0);

        }

        else if (rotation <= Math.PI) {

          context.translate(canvas.width, -costheta * canvas.oImage.height);

        }

        else if (rotation <= 1.5 * Math.PI) {

          context.translate(-costheta * canvas.oImage.width, canvas.height);

        }

        else {

          context.translate(0, -sintheta * canvas.oImage.width);

        }

        context.rotate(rotation);

        context.drawImage(canvas.oImage, 0, 0, canvas.oImage.width, canvas.oImage.height);

        context.restore();

      }

      canvas.id = p.id;

      canvas.angle = p.angle;

      p.parentNode.replaceChild(canvas, p);

    }

//向右旋转

    function rotateRight(id, angle) {

      rotate(id, angle == undefined ? 90 : angle);

    }

    //向左旋转

    function rotateLeft(id, angle) {

      rotate(id, angle == undefined ? -90 : -angle);

    }

  </script>

调用方法：

<div class="content">

  <div class="data">

    <a href="javascript:void(0)" style="font-weight: bold; text-decoration: none; font-size: 16px;"

      onclick="rotateRight(‘theimage‘,90);">右转</a> 
    <a href="javascript:void(0)" style="font-weight: bold; font-size: 16px; text-decoration: none;" 
      onclick="rotateLeft(‘theimage‘,90);">左转</a><br>    
      <img src="a.jpg" id="theimage" onload="resizeimg(this,this.width,this.height)" width="100%" alt="800×1422" style="cursor: pointer;" />

    </a>

    <div style="clear: both">

    </div>

  </div>

</div>

js图片旋转,布布扣,bubuko.com