On Dec 30, 5:09 am, Daniel Drozdzewski <[email protected]> wrote: > > On Dec 29, 1:18 am, Paul <[email protected]> wrote: > >> Hi all. I am writing an app that will convert touchscreen user inputs > >> (such as the user 'handwriting' on the screen) into vectors that can > >> then be saved and recalled later. I need to get the vectors into a > >> format I can store locally, either as a file or in an SQLite > >> database. Just wondering if anyone had any pointers as to how to get > >> started... my initial thought was to listen for MotionEvents and when > >> an ACTION_DOWN is detected, record the coordinates and use this as the > >> vector's start point, and then record intermediate coordinates as the > >> ACTION_MOVE is triggered (used to help define the shape of this Path > >> they are creating), ending the stroke vector on ACTION_UP... but this > >> results in many many intermediate points per vector (30 or 40) and > >> with several hundred vectors (a full page of handwritten text on a > >> tablet for example) this solution gets quickly out of hand as each > >> page will potentially require tens of thousands of points... > > >> Any suggestions on a better way to represent and store user-inputed > >> vectors/paths? Or maybe another approach completely? > > >> Thanks for any help! > > >> Paul > > Paul, > > You could blindingly start filtering any intermediate vectors, but you > would miss some important points, where the writing drastically > changes its direction. > As you see, the problem you have is detecting where the continuous > line changes its direction by much and intermediate points could be > filtered. > > You would need calculating the angles between adjacent vectors and > when the angle gets bigger than some threshold value, the point > between said vectors becomes very important. > > Hope this helps you somehow. > > -- > Daniel Drozdzewski
I was thinking about this issue too... how do I recognize when a path backs onto itself, makes sharp turns, etc as is normal in handwriting? As I mentioned in another reply, I have looked at the SVG Path standard: http://www.w3schools.com/svg/svg_path.asp Looks like a possibility in terms of efficiently storing the shape of the stroke, but to use it I need to somehow take a set of coordinate points that Android spits out from MotionEvent and 'recognize' when it is a curve, arc, etc... maybe I extend my StrokeGestureDetector I mentioned to handle the heavy lifting of this recognitions, so that it simply reports back when the stroke is curved, etc? The issue remains how I determine when a set of x,y coords forms a curve, a sharp curve (such as when printing an M for example), etc. Off the top of my head, maybe in my gesture detector, when in a stroke, store the last 3 MotionEvent points, generate a 'line' from point 1 to 2, and point 2 to 3 and determine the angle at this vertex to help recognize direction changes? Again, the HOW is where I am stuck at this point... once I have the points described, recreating looks straight- forward simple using the built-in Path class. Any ideas on how to programatically test for the direction changes, curves, etc? Paul -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
