车牌识别之字符分割

//! 找出指示城市的字符的Rect，例如苏A7003X，就是"A"的位置
int CCharsSegment::GetSpecificRect(const vector<Rect>& vecRect) {
  vector<int> xpositions;
  int maxHeight = 0;
  int maxWidth = 0;

  for (size_t i = 0; i < vecRect.size(); i++) {
    xpositions.push_back(vecRect[i].x);

    if (vecRect[i].height > maxHeight) {
      maxHeight = vecRect[i].height;
    }
    if (vecRect[i].width > maxWidth) {
      maxWidth = vecRect[i].width;
    }
  }

  int specIndex = 0;
  for (size_t i = 0; i < vecRect.size(); i++) {
    Rect mr = vecRect[i];
    int midx = mr.x + mr.width / 2;

    //如果一个字符有一定的大小，并且在整个车牌的1/7到2/7之间，则是我们要找的特殊字符
    //当前字符和下个字符的距离在一定的范围内
    if ((mr.width > maxWidth * 0.8 || mr.height > maxHeight * 0.8) &&
        (midx < int(m_theMatWidth / 7) * 2 &&
         midx > int(m_theMatWidth / 7) * 1)) {
      specIndex = i;
    }
  }

  return specIndex;
}

1   Mat tmpMat = input(Rect_<double>(w * 0.1, h * 0.1, w * 0.8, h * 0.8));
2 
3   // 判断车牌颜色以此确认threshold方法
4   Color plateType = getPlateType(tmpMat, true);

// getPlateType
//判断车牌的类型
Color getPlateType(const Mat& src, const bool adaptive_minsv) {
  float max_percent = 0;
  Color max_color = UNKNOWN;

  float blue_percent = 0;
  float yellow_percent = 0;
  float white_percent = 0;

  if (plateColorJudge(src, BLUE, adaptive_minsv, blue_percent) == true) {
    // cout << "BLUE" << endl;
    return BLUE;
  } else if (plateColorJudge(src, YELLOW, adaptive_minsv, yellow_percent) ==
             true) {
    // cout << "YELLOW" << endl;
    return YELLOW;
  } else if (plateColorJudge(src, WHITE, adaptive_minsv, white_percent) ==
             true) {
    // cout << "WHITE" << endl;
    return WHITE;
  } else {
    // cout << "OTHER" << endl;

    // 如果任意一者都不大于阈值，则取值最大者
    max_percent = blue_percent > yellow_percent ? blue_percent : yellow_percent;
    max_color = blue_percent > yellow_percent ? BLUE : YELLOW;

    max_color = max_percent > white_percent ? max_color : WHITE;
    return max_color;
  }
}

//! 这个函数做两个事情
//  1.把特殊字符Rect左边的全部Rect去掉，后面再重建中文字符的位置。
//  2.从特殊字符Rect开始，依次选择6个Rect，多余的舍去。
int CCharsSegment::RebuildRect(const vector<Rect>& vecRect,
                               vector<Rect>& outRect, int specIndex) {
  int count = 6;
  for (size_t i = specIndex; i < vecRect.size() && count; ++i, --count) {
    outRect.push_back(vecRect[i]);
  }

  return 0;
}

//去除车牌上方的钮钉
//计算每行元素的阶跃数，如果小于X认为是柳丁，将此行全部填0（涂黑）
// X的推荐值为，可根据实际调整
bool clearLiuDing(Mat& img) {
  vector<float> fJump;
  int whiteCount = 0;
  const int x = 7;
  Mat jump = Mat::zeros(1, img.rows, CV_32F);
  for (int i = 0; i < img.rows; i++) {
    int jumpCount = 0;

    for (int j = 0; j < img.cols - 1; j++) {
      if (img.at<char>(i, j) != img.at<char>(i, j + 1)) jumpCount++;

      if (img.at<uchar>(i, j) == 255) {
        whiteCount++;
      }
    }

    jump.at<float>(i) = (float)jumpCount;
  }

  int iCount = 0;
  for (int i = 0; i < img.rows; i++) {
    fJump.push_back(jump.at<float>(i));
    if (jump.at<float>(i) >= 16 && jump.at<float>(i) <= 45) {
      //车牌字符满足一定跳变条件
      iCount++;
    }
  }

  ////这样的不是车牌
  if (iCount * 1.0 / img.rows <= 0.40) {
    //满足条件的跳变的行数也要在一定的阈值内
    return false;
  }
  //不满足车牌的条件
  if (whiteCount * 1.0 / (img.rows * img.cols) < 0.15 ||
      whiteCount * 1.0 / (img.rows * img.cols) > 0.50) {
    return false;
  }

  for (int i = 0; i < img.rows; i++) {
    if (jump.at<float>(i) <= x) {
      for (int j = 0; j < img.cols; j++) {
        img.at<char>(i, j) = 0;
      }
    }
  }
  return true;
}