I used a neural net to do this sort of thing. My gesture was made with a class called Tracer:
Code:

//Line drawing class
class Tracer{
  Vec2 [] vectors;
  Tracer(){
  }
  Tracer(int len){
    vectors = new Vec2[len];
  }
  void initVectors(Vec2 [] input){
    //if the path is too short, double its length and interpolate vectors
    while(input.length < vectors.length){
	Vec2 [] temp = copyVec2(input);
	input = new Vec2[(temp.length*2)-1];
	for(int i = 0; i < temp.length-1; i++){
	  input[i*2] = temp[i];
	  input[i*2+1] = temp[i].midPoint(temp[i+1]);
	}
	input[input.length-1] = temp[temp.length-1];
    }
    //take points along the input as our path
    if (input.length > vectors.length){
	float step = (float)input.length/vectors.length;
	float j = 0.0;
	for(int i = 0; i < vectors.length; i++){
	  vectors[i] = input[(int)j];
	  j += step;
	}
    }
  }
  void draw(){
    if(tracer.vectors[0] != null){
	beginShape(LINE_STRIP);
	for(int i = 0; i < vectors.length; i++)
	  vertex(vectors[i].x,vectors[i].y);
	endShape();
    }
  }
}
 

I just took a line of points and then calculated the angle at each point. Then I compared that list of angles to the one I had stored. Thus, big square or small square, the angles in the points that go into making it are roughly the same as the square I drew in memory.

The neural net basically allows you to identify sloppy answers, but I'm sure you could bypass it (don't learn neural nets unless you really have to) by just taking the nearest rough answer (look up fuzzy logic).

The neural net gesture recognition is here.

The line was always taken as one long snap shot. I let the user drag the mouse to generate the line and on mouse release I capture. If it's too short then I walk along the points filling in enough points to make the length. Too long then I jump along the path missing surplus points. But that's all there in the code above anyway.

How do you mean a different point? Since the line is an array of a class called Vec2 (x, y), I guess you would just pick a member out from the array and change it's x,y value.

That's more confusing than stupid. I assume you mean from points.

Code:

// Function from Vec2 class in Gesture sketch
float arcTan2(Vec2 other){
  float dx = other.x - this.x;
  float dy = other.y - this.y;
  return atan2(dy,dx);
}

// Method for getting an array of angles from an array of Vec2s in gesture sketch
float [] atan2Vec2(Vec2 [] vectors){
    float [] atan2Return = new float[vectors.length-1];
    for(int i = 1; i < vectors.length; i++)
	atan2Return[i-1] = vectors[i-1].arcTan2(vectors[i]);
    return atan2Return;
}
 

or

Code:

float [] myAngles = {TWO_PI, HALF_PI, 3.6, 0.1};