"

From 2014.igem.org

jQuery.fn.rotate = function(angle,whence) {

   var p = this.get(0);

   // we store the angle inside the image tag for persistence
   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.round(Math.cos(rotation) * 1000) / 1000;
   var sintheta = Math.round(Math.sin(rotation) * 1000) / 1000;
   //alert(costheta+","+sintheta);

   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;
       }

       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);

}

jQuery.fn.rotateRight = function(angle) {

   this.rotate(angle==undefined?90:angle);

}

jQuery.fn.rotateLeft = function(angle) {

   this.rotate(angle==undefined?-90:-angle);

}