--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/tesseract/src/lstm/convolve.h	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,71 @@
+///////////////////////////////////////////////////////////////////////
+// File:        convolve.h
+// Description: Convolutional layer that stacks the inputs over its rectangle
+//              and pulls in random data to fill out-of-input inputs.
+//              Output is therefore same size as its input, but deeper.
+// Author:      Ray Smith
+//
+// (C) Copyright 2014, Google Inc.
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+///////////////////////////////////////////////////////////////////////
+
+#ifndef TESSERACT_LSTM_CONVOLVE_H_
+#define TESSERACT_LSTM_CONVOLVE_H_
+
+#include "matrix.h"
+#include "network.h"
+
+namespace tesseract {
+
+// Makes each time-step deeper by stacking inputs over its rectangle. Does not
+// affect the size of its input. Achieves this by bringing in random values in
+// out-of-input areas.
+class Convolve : public Network {
+public:
+  // The area of convolution is 2*half_x + 1 by 2*half_y + 1, forcing it to
+  // always be odd, so the center is the current pixel.
+  TESS_API
+  Convolve(const std::string &name, int ni, int half_x, int half_y);
+  ~Convolve() override = default;
+
+  std::string spec() const override {
+    return "C" + std::to_string(half_y_ * 2 + 1) + "," + std::to_string(half_x_ * 2 + 1);
+  }
+
+  // Writes to the given file. Returns false in case of error.
+  bool Serialize(TFile *fp) const override;
+  // Reads from the given file. Returns false in case of error.
+  bool DeSerialize(TFile *fp) override;
+
+  // Runs forward propagation of activations on the input line.
+  // See Network for a detailed discussion of the arguments.
+  void Forward(bool debug, const NetworkIO &input, const TransposedArray *input_transpose,
+               NetworkScratch *scratch, NetworkIO *output) override;
+
+  // Runs backward propagation of errors on the deltas line.
+  // See Network for a detailed discussion of the arguments.
+  bool Backward(bool debug, const NetworkIO &fwd_deltas, NetworkScratch *scratch,
+                NetworkIO *back_deltas) override;
+
+private:
+  void DebugWeights() override {
+    tprintf("Must override Network::DebugWeights for type %d\n", type_);
+  }
+
+protected:
+  // Serialized data.
+  int32_t half_x_;
+  int32_t half_y_;
+};
+
+} // namespace tesseract.
+
+#endif // TESSERACT_LSTM_SUBSAMPLE_H_