Letter Match Example

ShapeLogic comes with a test application for letter matching, the purpose of which is to show how to use the ShapeLogic framework on a simple well defined problem.

Currently 4 sets of rules have been defined:

  1. Recognition of straight capital letters in ShapeLogic 0.2
  2. Recognition of all capital letters starting in ShapeLogic 0.7
  3. Simplified syntax by adding a filter logic language starting in ShapeLogic 0.8
  4. Using lazy stream and filter logic language starting in ShapeLogic 1.0

The matching example is not very robust yet, and is made to match letter in sans serif typefaces, e.g. Ariel or Helvetica.

Unit tests exist for all capital letters.

Matched images can be found in this directory:

shapelogic/src/test/resources/images/smallThinLetters

How to see letter recognition in action

See the Getting Started page.

Recognition of all capital letters in ShapeLogic 1.0

Lines and points are annotated in order to match curves, circle arches or Bezier curves are not used. Lines and points can be filtered according to both position in the bounding box for a polygon, and point and line annotations.

Rules for the letter A in ShapeLogic 1.0

For a better description of logic language syntax.

rule("A", POINT_COUNT, "==", 5., letterFilter);
rule("A", HOLE_COUNT, "==", 1., letterFilter);
rule("A", T_JUNCTION_LEFT_POINT_COUNT,"==", 1., letterFilter);
rule("A", T_JUNCTION_RIGHT_POINT_COUNT,"==", 1., letterFilter);
rule("A", END_POINT_BOTTOM_POINT_COUNT, "==", 2., letterFilter);
rule("A", HORIZONTAL_LINE_COUNT, "==", 1., letterFilter);
rule("A", VERTICAL_LINE_COUNT, "==", 0., letterFilter);
rule("A", END_POINT_COUNT, "==", 2., letterFilter);
rule("A", SOFT_POINT_COUNT, "==", 0., letterFilter);

The meaning of the rules for A is:

  1. There are 5 points
  2. There is 1 hole
  3. There is 1 T junction on the left half of the bounding box
  4. There is one T junction on the right half of the bounding box
  5. The number of end points in the bottom half is 2
  6. There is one horizontal line
  7. There are 0 vertical lines
  8. The total number of end points is 2
  9. There are no soft points

Rules for the letter C in ShapeLogic 0.8

new NumericRule("C", HOLE_COUNT, polygon, VAR + HOLE_COUNT_EX, "==", 0.),
new NumericRule("C", T_JUNCTION_POINT_COUNT, polygon, filter(T_JUNCTION_POINT_COUNT_EX), "==",0.),
new NumericRule("C", END_POINT_BOTTOM_POINT_COUNT, polygon, filter(END_POINT_BOTTOM_POINT_COUNT_EX), "==", 1.),
new NumericRule("C", MULTI_LINE_COUNT, polygon, size(MULTI_LINE_COUNT_EX), "==", 1.),
new NumericRule("C", VERTICAL_LINE_COUNT, polygon, size(VERTICAL_LINE_COUNT_EX), "==", 0.),
new NumericRule("C", END_POINT_COUNT, polygon, VAR + END_POINT_COUNT_EX, "==", 2.),
new NumericRule("C", INFLECTION_POINT_COUNT, polygon, size(INFLECTION_POINT_COUNT_EX), "==", 0.),
new NumericRule("C", CURVE_ARCH_COUNT, polygon, size(CURVE_ARCH_COUNT_ANN_EX), ">",1.),
new NumericRule("C", HARD_POINT_COUNT, polygon, filter(HARD_POINT_COUNT_EX), "==", 0.),
new NumericRule("C", SOFT_POINT_COUNT, polygon, size(SOFT_POINT_COUNT_ANN_EX), ">", 0.),

The meaning of the rules for C is:

  1. There is no holes
  2. There is no T junction
  3. There is 1 end point in the bottom half of the bounding box
  4. There is 1 multi line
  5. There are no vertical lines
  6. There are 2 end points
  7. There are 0 inflections points
  8. The there are more than 1 line annotated with curved arch
  9. There are no hard corners
  10. There are more than 0 soft points

Line annotation in LineType

        /** Before a type is determined */
        UNKNOWN,
        
        /** Not completely straight */
        STRAIGHT, //only a start and an end point

        /** only on one side of a line between the start and end point */
        CURVE_ARCH,

        /** On both sides of a line between the start and end point 
         * this is the rest category for lines */
        WAVE,

        /** Means that this is an arch and that it is concave compared to 1 or both 
         * neighbor points, meaning they are on the same side of the line as the 
         * arch */
        CONCAVE_ARCH,
        
        /** This line contains an inflection point, meaning the end points have 
         * different signed direction changes */
        INFLECTION_POINT,
        
        /** For multi lines, if 2 lines are added together */
        STRAIGHT_MULTI_LINE,

Point annotation in PointType

        /** Before a type is determined */
        UNKNOWN,
        
        /** If the point has a sharp angle for now 30 degrees is set as the limit */
        HARD_CORNER,

        /** If it is not a hard point */
        SOFT_POINT,
        
        /** 3 or more lines meets, U is for unknown */
        U_JUNCTION,
        
        /** 3 lines meet 2 are collinear and the last is somewhat orthogonal */
        T_JUNCTION,

        /** 3 lines meet less than 180 degrees between all of them */
        ARROW_JUNCTION,

        /** 3 lines meet, not a T junction */
        Y_JUNCTION,
        
        /** point is an end point, 
         * maybe later there should be a distinction between end points and have 
         * nothing else close by and end points that have close neighbors */
        END_POINT,