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    <p>I’m guessing the source image for your smaller circle is the same as the big circle--just unrotated.</p> <p>If that’s the case, you need to <strong>find your un-rotated mouseclick position.</strong></p> <p>Then you can clip your smaller circle around the unrotated mouseclick and rotate it into place.</p> <p>Given:</p> <ul> <li>Your original center of rotation is cx/cy,</li> <li>Your angle of rotation is radAngle (in radians)</li> <li>Your rotated mousclick point is rx/ry.</li> </ul> <p>You can calculate your un-rotated mouseclick position ( preRX / preRY ) like this:</p> <pre><code>// the bigger circle's rotation point var cx=150; var cy=150; // the rotation angle in radians var radAngle=Math.PI/6; // 30 degrees, for example // the rotated mouseclick point var rx=225; var ry=245; // the radius of the smaller circle var smallRadius=50; // calculate the unrotated mouseclick point var dx= rx-cx; var dy= ry-cy; var preRX= cx+ dx*Math.cos(-radAngle) - dy*Math.sin(-radAngle); var preRY= cy+ dy*Math.cos(-radAngle) + dx*Math.sin(-radAngle); </code></pre> <p>Then you make a clipping path using your smaller circle</p> <pre><code>// create a clipping path for the small circle ctx.arc(preRX,preRY,smallRadius,0,Math.PI*2,false); ctx.closePath(); ctx.clip(); </code></pre> <p>And finally translate + rotate and draw the clipped image into position</p> <pre><code>// rotate the small circle into position ctx.translate(cx,cy); ctx.rotate(radAngle); ctx.globalAlpha=1.0; ctx.drawImage(img,-img.width/2,-img.height/2); </code></pre> <p>Here is code and a Fiddle: <a href="http://jsfiddle.net/m1erickson/YAt5r/" rel="nofollow">http://jsfiddle.net/m1erickson/YAt5r/</a></p> <pre><code>&lt;!doctype html&gt; &lt;html&gt; &lt;head&gt; &lt;link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /&gt; &lt;!-- reset css --&gt; &lt;script type="text/javascript" src="http://code.jquery.com/jquery.min.js"&gt;&lt;/script&gt; &lt;style&gt; body{ background-color: ivory; } canvas{border:1px solid red;} &lt;/style&gt; &lt;script&gt; $(function(){ var canvas = document.getElementById('canvas'); var ctx=canvas.getContext("2d"); var img=new Image(); img.onload=function(){ draw(); } img.src="https://dl.dropboxusercontent.com/u/139992952/stackoverflow/house-icon.png"; function draw(){ // the bigger circle's rotation point var cx=150; var cy=150; // the rotation angle in radians var radAngle=Math.PI/6; // 30 degrees // the rotated mouseclick point var rx=225; var ry=245; // the radius of the smaller circle var smallRadius=50; // calculate the unrotated mouseclick point var dx= rx-cx; var dy= ry-cy; var preRX= cx+ dx*Math.cos(-radAngle) - dy*Math.sin(-radAngle); var preRY= cy+ dy*Math.cos(-radAngle) + dx*Math.sin(-radAngle); // test // rotate the original image and draw it ctx.save(); ctx.translate(cx,cy); ctx.rotate(radAngle); ctx.globalAlpha=.25; ctx.drawImage(img,-img.width/2,-img.height/2); ctx.restore(); // clip the smaller image, rotate it and draw it ctx.save(); ctx.beginPath(); // create a clipping path for the small circle ctx.arc(preRX,preRY,smallRadius,0,Math.PI*2,false); ctx.closePath(); ctx.clip(); // rotate the small circle into position ctx.translate(cx,cy); ctx.rotate(radAngle); ctx.globalAlpha=1.0; ctx.drawImage(img,-img.width/2,-img.height/2); // stroke the circle ctx.arc(preRX,preRY,smallRadius,0,Math.PI*2,false); ctx.stroke(); ctx.restore(); } }); // end $(function(){}); &lt;/script&gt; &lt;/head&gt; &lt;body&gt; &lt;p&gt;Original image is 25% opacity&lt;/p&gt; &lt;p&gt;Clipped overlay image is 100% opacity&lt;/p&gt; &lt;canvas id="canvas" width=350 height=350&gt;&lt;/canvas&gt; &lt;/body&gt; &lt;/html&gt; </code></pre>
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