<p>I would think you will need to generate probabilities for what text character the input is. If the highest probability text character is below some threshold, classify the stroke as drawing.</p>

<p>This is a possible useful paper: <a href="http://arxiv.org/pdf/1304.0421v1.pdf" rel="nofollow">http://arxiv.org/pdf/1304.0421v1.pdf</a> (if only for its reference list).  Also the first hit on this google scholar search looks relevant: <a href="http://scholar.google.com/scholar?q=classification+stroke+input+text+or+drawing" rel="nofollow">http://scholar.google.com/scholar?q=classification+stroke+input+text+or+drawing</a></p>
Classifying stroke input as text or drawing
<p>I'm interested in taking user stroke input (i.e. drawing with an iPad) and classifying it as either text or a drawing (or, I suppose, just non-text), in whatever capacity is reasonably feasible. I'm not expecting a pre-built library for this, I'm just having a hard time finding any papers or algorithmic resources about this.</p>

<p>I don't need to detect what the text is that they're drawing, just whether it's likely text or not.</p>