四步写出一个简单的手游手写识别算法

04月

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井号键编译

　　如何写一个简单的手写识别算法，可以精准快速的识别出自定义的简单图形：

　　把所有的笔画定义了个8个方向，然后将B的笔画可以分解成一个字符串。然后当人在触摸屏上画出一个符号时，也将它分解成8个方向的字符串，最后比较两个字符串的距离就能判断出和不同符号的近似度。

　　实现起来也很简单，第一步去噪，因为不同触摸屏的采样频率不同。

　　实现代码：

void GestureAlgorithm::addPoint(int x, int y){int d_x, d_y;
d_x = x-positions.back().x;d_y = y-positions.back().y;
if( d_x*d_x + d_y*d_y >= MIN_MOVEMENT){updateStatistic(x, y);recognizeGesture();}}
void GestureAlgorithm::updateStatistic(int x, int y){positions.push_back(Point(x, y));point_num = positions.size();if(point_num >1){// For Point Recognizationdist_sum += positions.begin()->dist(x,y);dist_average =dist_sum/(point_num - 1);
// For Line Recognization// Need a patch for the V0 calculation.Point v0 = Point(positions[1].x - positions[0].x, positions[0].y );Point v1 = Point(x - positions[0].x, y -positions[0].y);if(normalize(v0) normalize( v1)){float theta = acos(dot(v0, v1));theta_sum += theta;theta_sqsum += sq(theta);theta_average = theta_sum / (float)(point_num - 1);theta_factor = sqrt((float)(point_num - 1)*theta_sqsum - sq(theta_sum))/(point_num-1);}}mainDirections = detectDirection(positions);
//Statistic Updatepos_x_sum += x;pos_y_sum += y;pos_xx_sum += sq(x);pos_xy_sum += x * y;
midPoint = Point(pos_x_sum/point_num, pos_y_sum/point_num);curGestureRender->render_bbox->addPoint(x, y);}

　　实现代码：

PosList GestureAlgorithm::limitDirections(const PosList positions)
- {
  - PosList res;
    - int lastx, lasty;
      - bool firstTime = true;
        
        for( PosList::const_iterator ii = positions.begin(); ii != positions.end(); ++ii )
        {
        if( firstTime )
        {
        lastx = ii->x;
        lasty = ii->y;
        
        firstTime = false;
        }
        else
        {
        int dx, dy;
        
        dx = ii->x – lastx;
        dy = ii->y – lasty;
        
        if( dy > 0 )
        {
        if( dx > dy -dx > dy )
        dy = 0;
        else
        dx = 0;
        }
        else
        {
        if( dx > -dy -dx > -dy )
        dy = 0;
        else
        dx = 0;
        }
        res.push_back( Point( dx, dy ) );
        lastx = ii->x;
        lasty = ii->y;
        }
        }
        
        return res;
        }

　　实现代码：

Position Num:141
- X=113 Y= 0
  - X= 0 Y= -15
    - X=0 Y= 179
      - X= 13 Y= 0
        X=-110 Y= 0
        X= 0 Y= 6
        X=0 Y= -101
        X= 3 Y= 0
        Directions Number: 8
        Directions Length:540
        UP Number: 3 Down Number: 2 Left: 1 right 2
        Position Num:142

　　实现代码：

PosList GestureAlgorithm::removeShortestNoise(const PosList positions)
- {
  - PosList res;
    - int shortestSoFar;
      - PosList::const_iterator shortest;
        bool firstTime = true;
        
        for( PosList::const_iterator ii = positions.begin(); ii != positions.end(); ++ii )
        {
        if( firstTime )
        {
        shortestSoFar = ii->x*ii->x + ii->y*ii->y;
        shortest = ii;
        
        firstTime = false;
        }
        else
        {
        if( (ii->x*ii->x + ii->y*ii->y) < shortestSoFar ) { shortestSoFar = ii->x*ii->x + ii->y*ii->y;
        shortest = ii;
        }
        }
        }
        
        for( PosList::const_iterator ii = positions.begin(); ii != positions.end(); ++ii )
        {
        if( ii != shortest)
        res.push_back( *ii );
        }
        
        return res;
        }
        
        PosList GestureAlgorithm::detectDirection(const PosList positions)
        {
        PosList directions = simplify(limitDirections(positions));
        double minLength = calcLength(directions) *minMatch;
        
        while(directions.size() > 0 calcLength(removeShortestNoise(directions)) > minLength)
        {
        directions = simplify(removeShortestNoise(directions));
        }
        
        upNum = 0; downNum = 0; leftNum = 0; rightNum =0;
        for(int i = 0; i< directions.size(); i++) { if(directions[i].y >= 0 directions[i].x ==0)
        upNum++;
        else if(directions[i].y < 0 directions[i].x ==0) downNum++; else if(directions[i].x >= 0 directions[i].y ==0 )
        leftNum++;
        else if(directions[i].x < 0 directions[i].y ==0 )
        rightNum++;
        }
        return directions;
        }

复制代码
　　这个算法的厉害之处是可以实时识别，画到一半也能判断出来。

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