 <p>An interface for recording graphical operations.</p>
<p><a href="dart-ui/Canvas-class.html">Canvas</a> objects are used in creating <a href="dart-ui/Picture-class.html">Picture</a> objects, which can
themselves be used with a <a href="dart-ui/SceneBuilder-class.html">SceneBuilder</a> to build a <a href="dart-ui/Scene-class.html">Scene</a>. In
normal usage, however, this is all handled by the framework.</p>
<p>A canvas has a current transformation matrix which is applied to all
operations. Initially, the