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));

  }

}