renderer.h

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// File:        renderer.h
// Description: Rendering interface to inject into TessBaseAPI
//
// (C) Copyright 2011, 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_API_RENDERER_H_
#define TESSERACT_API_RENDERER_H_

// To avoid collision with other typenames include the ABSOLUTE MINIMUM
// complexity of includes here. Use forward declarations wherever possible
// and hide includes of complex types in baseapi.cpp.
#include <string>  // for std::string
#include "genericvector.h"
#include "platform.h"

struct Pix;

namespace tesseract {

class TessBaseAPI;

class TESS_API TessResultRenderer {
 public:
  virtual ~TessResultRenderer();

  // Takes ownership of pointer so must be new'd instance.
  // Renderers aren't ordered, but appends the sequences of next parameter
  // and existing next(). The renderers should be unique across both lists.
  void insert(TessResultRenderer* next);

  // Returns the next renderer or nullptr.
  TessResultRenderer* next() {
    return next_;
  }

  bool BeginDocument(const char* title);

  bool AddImage(TessBaseAPI* api);

  bool EndDocument();

  const char* file_extension() const {
    return file_extension_;
  }
  const char* title() const {
    return title_.c_str();
  }

  // Is everything fine? Otherwise something went wrong.
  bool happy() {
    return happy_;
  }

  int imagenum() const {
    return imagenum_;
  }

 protected:
  TessResultRenderer(const char* outputbase, const char* extension);

  // Hook for specialized handling in BeginDocument()
  virtual bool BeginDocumentHandler();

  // This must be overridden to render the OCR'd results
  virtual bool AddImageHandler(TessBaseAPI* api) = 0;

  // Hook for specialized handling in EndDocument()
  virtual bool EndDocumentHandler();

  // Renderers can call this to append '\0' terminated strings into
  // the output string returned by GetOutput.
  // This method will grow the output buffer if needed.
  void AppendString(const char* s);

  // Renderers can call this to append binary byte sequences into
  // the output string returned by GetOutput. Note that s is not necessarily
  // '\0' terminated (and can contain '\0' within it).
  // This method will grow the output buffer if needed.
  void AppendData(const char* s, int len);

 private:
  const char* file_extension_;  // standard extension for generated output
  STRING title_;                // title of document being renderered
  int imagenum_;                // index of last image added

  FILE* fout_;                // output file pointer
  TessResultRenderer* next_;  // Can link multiple renderers together
  bool happy_;                // I get grumpy when the disk fills up, etc.
};

class TESS_API TessTextRenderer : public TessResultRenderer {
 public:
  explicit TessTextRenderer(const char* outputbase);

 protected:
  bool AddImageHandler(TessBaseAPI* api) override;
};

class TESS_API TessHOcrRenderer : public TessResultRenderer {
 public:
  explicit TessHOcrRenderer(const char* outputbase, bool font_info);
  explicit TessHOcrRenderer(const char* outputbase);

 protected:
  bool BeginDocumentHandler() override;
  bool AddImageHandler(TessBaseAPI* api) override;
  bool EndDocumentHandler() override;

 private:
  bool font_info_;  // whether to print font information
};

class TESS_API TessAltoRenderer : public TessResultRenderer {
 public:
  explicit TessAltoRenderer(const char* outputbase);

 protected:
  bool BeginDocumentHandler() override;
  bool AddImageHandler(TessBaseAPI* api) override;
  bool EndDocumentHandler() override;
};

class TESS_API TessTsvRenderer : public TessResultRenderer {
 public:
  explicit TessTsvRenderer(const char* outputbase, bool font_info);
  explicit TessTsvRenderer(const char* outputbase);

 protected:
  bool BeginDocumentHandler() override;
  bool AddImageHandler(TessBaseAPI* api) override;
  bool EndDocumentHandler() override;

 private:
  bool font_info_;  // whether to print font information
};

class TESS_API TessPDFRenderer : public TessResultRenderer {
 public:
  // datadir is the location of the TESSDATA. We need it because
  // we load a custom PDF font from this location.
  TessPDFRenderer(const char* outputbase, const char* datadir,
                  bool textonly = false);

 protected:
  bool BeginDocumentHandler() override;
  bool AddImageHandler(TessBaseAPI* api) override;
  bool EndDocumentHandler() override;

 private:
  // We don't want to have every image in memory at once,
  // so we store some metadata as we go along producing
  // PDFs one page at a time. At the end, that metadata is
  // used to make everything that isn't easily handled in a
  // streaming fashion.
  long int obj_;                     // counter for PDF objects
  GenericVector<long int> offsets_;  // offset of every PDF object in bytes
  GenericVector<long int> pages_;    // object number for every /Page object
  std::string datadir_;              // where to find the custom font
  bool textonly_;                    // skip images if set
  // Bookkeeping only. DIY = Do It Yourself.
  void AppendPDFObjectDIY(size_t objectsize);
  // Bookkeeping + emit data.
  void AppendPDFObject(const char* data);
  // Create the /Contents object for an entire page.
  char* GetPDFTextObjects(TessBaseAPI* api, double width, double height);
  // Turn an image into a PDF object. Only transcode if we have to.
  static bool imageToPDFObj(Pix* pix, const char* filename, long int objnum,
                            char** pdf_object, long int* pdf_object_size,
                            int jpg_quality);
};

class TESS_API TessUnlvRenderer : public TessResultRenderer {
 public:
  explicit TessUnlvRenderer(const char* outputbase);

 protected:
  bool AddImageHandler(TessBaseAPI* api) override;
};

class TESS_API TessLSTMBoxRenderer : public TessResultRenderer {
 public:
  explicit TessLSTMBoxRenderer(const char* outputbase);

 protected:
  bool AddImageHandler(TessBaseAPI* api) override;
};

class TESS_API TessBoxTextRenderer : public TessResultRenderer {
 public:
  explicit TessBoxTextRenderer(const char* outputbase);

 protected:
  bool AddImageHandler(TessBaseAPI* api) override;
};

class TESS_API TessWordStrBoxRenderer : public TessResultRenderer {
 public:
  explicit TessWordStrBoxRenderer(const char* outputbase);

 protected:
  bool AddImageHandler(TessBaseAPI* api) override;
};

#ifndef DISABLED_LEGACY_ENGINE

class TESS_API TessOsdRenderer : public TessResultRenderer {
 public:
  explicit TessOsdRenderer(const char* outputbase);

 protected:
  bool AddImageHandler(TessBaseAPI* api) override;
};

#endif  // ndef DISABLED_LEGACY_ENGINE

}  // namespace tesseract.

#endif  // TESSERACT_API_RENDERER_H_