sclass ChessOCR_SquareImagesCollector {
  new Set<S> imageMD5s;
  L<ChessOCR_PieceImage> allImages = syncList();
  
  VF2<S, Rect> onBoardFound; // image name, board rects
  
  void loadImagesFromAGIBlue {
    for (S name, fen : unpair agiBlue_chess_trainingImagesWithPositions()) {
      SS map = pairsToCIMap(agiBlue_lookupMultipleKeys(agiBlue_chessBoardRecognitionTrainingImagesSliceID(),
        name, ll("Input image", "Segmenter used", "Chess board found", "Board location")));
      if (!isYes(map.get("Chess board found"))) continue with print("Chess board not found, skipping");
      BufferedImage img = loadImage2(parseImageSnippetURL(map.get("input image")));
      Rect r = safeUnstructRect(map.get("Board location"));
      if (r == null) continue with print("No board? Skipping");
      print("Board: " + r.w + "*" + r.h);
      callF(onBoardFound, name, r);
      if (abs(r.w-r.h) > 3) continue with print("Board not square, skipping");
      BufferedImage board = clipBufferedImage(img, r);
      LS position = chess_parseFEN(fen);
      printStruct(+position);
      
      LL<BufferedImage> squareImages = map2 cloneBufferedImage(bufferedImageMNGrid(board, 8, 8));
    
      for row to 8: {
        S fenLine = position.get(row);
        L<BufferedImage> images = squareImages.get(row);
        for col to 8:
          if (imageMD5s.add(imageMD5(images.get(col))))
            allImages.add(new ChessOCR_PieceImage(
              chess_xyToSquare(col, row),
              chess_parseFENSymbol(fenLine.charAt(col)),
              images.get(col)));
      }
    }
    
    print("Have " + n2(allImages, "chess square image"));
  }
  
  LPair<S, BufferedImage> allImages() {
    ret map(cloneList(allImages), i -> pair(i.piece, i.img));
  }
}