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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;
/**
* Interface for rendering tesseract results into a document, such as text,
* HOCR or pdf. This class is abstract. Specific classes handle individual
* formats. This interface is then used to inject the renderer class into
* tesseract when processing images.
*
* For simplicity implementing this with tesesract version 3.01,
* the renderer contains document state that is cleared from document
* to document just as the TessBaseAPI is. This way the base API can just
* delegate its rendering functionality to injected renderers, and the
* renderers can manage the associated state needed for the specific formats
* in addition to the heuristics for producing it.
*/
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_;
}
/**
* Starts a new document with the given title.
* This clears the contents of the output data.
* Title should use UTF-8 encoding.
*/
bool BeginDocument(const char* title);
/**
* Adds the recognized text from the source image to the current document.
* Invalid if BeginDocument not yet called.
*
* Note that this API is a bit weird but is designed to fit into the
* current TessBaseAPI implementation where the api has lots of state
* information that we might want to add in.
*/
bool AddImage(TessBaseAPI* api);
/**
* Finishes the document and finalizes the output data
* Invalid if BeginDocument not yet called.
*/
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_;
}
/**
* Returns the index of the last image given to AddImage
* (i.e. images are incremented whether the image succeeded or not)
*
* This is always defined. It means either the number of the
* current image, the last image ended, or in the completed document
* depending on when in the document lifecycle you are looking at it.
* Will return -1 if a document was never started.
*/
int imagenum() const {
return imagenum_;
}
protected:
/**
* Called by concrete classes.
*
* outputbase is the name of the output file excluding
* extension. For example, "/path/to/chocolate-chip-cookie-recipe"
*
* extension indicates the file extension to be used for output
* files. For example "pdf" will produce a .pdf file, and "hocr"
* will produce .hocr files.
*/
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.
};
/**
* Renders tesseract output into a plain UTF-8 text string
*/
class TESS_API TessTextRenderer : public TessResultRenderer {
public:
explicit TessTextRenderer(const char* outputbase);
protected:
bool AddImageHandler(TessBaseAPI* api) override;
};
/**
* Renders tesseract output into an hocr text string
*/
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
};
/**
* Renders tesseract output into an alto text string
*/
class TESS_API TessAltoRenderer : public TessResultRenderer {
public:
explicit TessAltoRenderer(const char* outputbase);
protected:
bool BeginDocumentHandler() override;
bool AddImageHandler(TessBaseAPI* api) override;
bool EndDocumentHandler() override;
};
/**
* Renders Tesseract output into a TSV string
*/
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
};
/**
* Renders tesseract output into searchable PDF
*/
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);
};
/**
* Renders tesseract output into a plain UTF-8 text string
*/
class TESS_API TessUnlvRenderer : public TessResultRenderer {
public:
explicit TessUnlvRenderer(const char* outputbase);
protected:
bool AddImageHandler(TessBaseAPI* api) override;
};
/**
* Renders tesseract output into a plain UTF-8 text string for LSTMBox
*/
class TESS_API TessLSTMBoxRenderer : public TessResultRenderer {
public:
explicit TessLSTMBoxRenderer(const char* outputbase);
protected:
bool AddImageHandler(TessBaseAPI* api) override;
};
/**
* Renders tesseract output into a plain UTF-8 text string
*/
class TESS_API TessBoxTextRenderer : public TessResultRenderer {
public:
explicit TessBoxTextRenderer(const char* outputbase);
protected:
bool AddImageHandler(TessBaseAPI* api) override;
};
/**
* Renders tesseract output into a plain UTF-8 text string in WordStr format
*/
class TESS_API TessWordStrBoxRenderer : public TessResultRenderer {
public:
explicit TessWordStrBoxRenderer(const char* outputbase);
protected:
bool AddImageHandler(TessBaseAPI* api) override;
};
#ifndef DISABLED_LEGACY_ENGINE
/**
* Renders tesseract output into an osd text string
*/
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_
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