A portion of my app involves the user drawing images that will be later strung together in a PDF. The user is free to use the entire screen to draw. Once the user is done drawing, I’d like to trim off all of the white space before adding the image to a PDF. This is where I am having problems. I’ve thought of two different methods to determine the location of trimmable white space and both seem clumsy.
My first thought was having the motion event of the stylus record if the event has gone outside of the box so far. If it has, I would expand the box to accommodate this. Unfortunately I could see polling every time there is a motion event being bad for performance. I can’t just look at up and down events because the user could draw something like the letter V.
Then I thought I could look at all the pixels (using getPixel()) and see where the highest, lowest, rightmost and leftmost black pixels are. Again this seems like a really inefficient way to find the box. I’m sure I could skip some pixels to improve performance, but I can’t skip too many.
Is there a standard way of doing what I want to do? I haven’t been able to find anything.
If the user is drawing, aren’t you already handling the onTouchEvent callback in order to capture the drawing events? If so, it shouldn’t be a big deal to keep a minX, maxX, minY and maxY and check each recorded drawing event against these values.