CreateBuffer

DROP FUNCTION IF EXISTS createBuffer;
CREATE FUNCTION createBuffer(ponto POINT, distancia INT) RETURNS POLYGON

    BEGIN
    /**
     *
     * @description : Function to create a circle around a given point and a radius in meters
     * @author : Fernando Norte (fnorte at gmail dot com)
     *
     * @params : ponto POINT (geometry), distancia INT (in meters)
     * @return : Polygon (geometry)
     *
     **/
        SET @angle = 0;
        SET @buffer = ''; # point collection string
        SET @firstPoint = ''; # to close to polygon
        SET @xP = X(ponto);  # Lat of given point
        SET @yP = Y(ponto); # Long of given point
        SET @radius = (distancia / 111200); # Conversion from meters to decimal degres (number to confirm)

        REPEAT
            # Algorithm to put the points around the center
            SET @Nx = @xP + @radius * COS(@angle);
            SET @Ny = @yP + @radius * SIN(@angle);

            # Concatenate the border point X,Y to the buffer string
            SET @buffer = CONCAT(@buffer, @Nx, ' ', @Ny, ', ');

            IF @angle = 0 THEN
                # reserve the first point collected to close the polygon
                SET @firstPoint = CONCAT(@Nx, ' ', @Ny);
            END IF;
            SET @angle = @angle + (2*PI()/20); # increment angle to put 20 points around the center
        UNTIL @angle >= (2*PI()) END REPEAT;

        # create WKT for the Polygon
        SET @buffer = CONCAT('POLYGON((', @buffer, @firstPoint, '))');

        RETURN GeomFromText(@buffer);

    END