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https://github.com/tesseract-ocr/tesseract.git
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228 lines
8.1 KiB
C++
228 lines
8.1 KiB
C++
///////////////////////////////////////////////////////////////////////
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// File: renderer.h
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// Description: Rendering interface to inject into TessBaseAPI
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//
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// (C) Copyright 2011, Google Inc.
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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///////////////////////////////////////////////////////////////////////
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#ifndef TESSERACT_API_RENDERER_H__
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#define TESSERACT_API_RENDERER_H__
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// To avoid collision with other typenames include the ABSOLUTE MINIMUM
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// complexity of includes here. Use forward declarations wherever possible
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// and hide includes of complex types in baseapi.cpp.
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#include "genericvector.h"
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#include "platform.h"
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#include "publictypes.h"
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namespace tesseract {
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class TessBaseAPI;
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/**
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* Interface for rendering tesseract results into a document, such as text,
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* HOCR or pdf. This class is abstract. Specific classes handle individual
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* formats. This interface is then used to inject the renderer class into
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* tesseract when processing images.
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*
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* For simplicity implementing this with tesesract version 3.01,
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* the renderer contains document state that is cleared from document
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* to document just as the TessBaseAPI is. This way the base API can just
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* delegate its rendering functionality to injected renderers, and the
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* renderers can manage the associated state needed for the specific formats
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* in addition to the heuristics for producing it.
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*/
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class TESS_API TessResultRenderer {
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public:
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virtual ~TessResultRenderer();
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// Takes ownership of pointer so must be new'd instance.
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// Renderers aren't ordered, but appends the sequences of next parameter
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// and existing next(). The renderers should be unique across both lists.
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void insert(TessResultRenderer* next);
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// Returns the next renderer or NULL.
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TessResultRenderer* next() { return next_; }
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/**
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* Starts a new document with the given title.
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* This clears the contents of the output data.
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*/
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bool BeginDocument(const char* title);
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/**
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* Adds the recognized text from the source image to the current document.
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* Invalid if BeginDocument not yet called.
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*
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* Note that this API is a bit weird but is designed to fit into the
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* current TessBaseAPI implementation where the api has lots of state
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* information that we might want to add in.
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*/
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bool AddImage(TessBaseAPI* api);
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/**
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* Finishes the document and finalizes the output data
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* Invalid if BeginDocument not yet called.
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*/
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bool EndDocument();
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const char* file_extension() const { return file_extension_; }
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const char* title() const { return title_; }
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/**
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* Returns the index of the last image given to AddImage
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* (i.e. images are incremented whether the image succeeded or not)
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*
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* This is always defined. It means either the number of the
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* current image, the last image ended, or in the completed document
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* depending on when in the document lifecycle you are looking at it.
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* Will return -1 if a document was never started.
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*/
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int imagenum() const { return imagenum_; }
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protected:
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/**
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* Called by concrete classes.
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*
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* outputbase is the name of the output file excluding
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* extension. For example, "/path/to/chocolate-chip-cookie-recipe"
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*
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* extension indicates the file extension to be used for output
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* files. For example "pdf" will produce a .pdf file, and "hocr"
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* will produce .hocr files.
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*/
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TessResultRenderer(const char *outputbase,
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const char* extension);
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// Hook for specialized handling in BeginDocument()
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virtual bool BeginDocumentHandler();
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// This must be overriden to render the OCR'd results
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virtual bool AddImageHandler(TessBaseAPI* api) = 0;
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// Hook for specialized handling in EndDocument()
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virtual bool EndDocumentHandler();
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// Renderers can call this to append '\0' terminated strings into
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// the output string returned by GetOutput.
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// This method will grow the output buffer if needed.
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void AppendString(const char* s);
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// Renderers can call this to append binary byte sequences into
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// the output string returned by GetOutput. Note that s is not necessarily
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// '\0' terminated (and can contain '\0' within it).
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// This method will grow the output buffer if needed.
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void AppendData(const char* s, int len);
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private:
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const char* file_extension_; // standard extension for generated output
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const char* title_; // title of document being renderered
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int imagenum_; // index of last image added
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FILE* fout_; // output file pointer
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TessResultRenderer* next_; // Can link multiple renderers together
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bool happy_; // I get grumpy when the disk fills up, etc.
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};
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/**
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* Renders tesseract output into a plain UTF-8 text string
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*/
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class TESS_API TessTextRenderer : public TessResultRenderer {
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public:
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explicit TessTextRenderer(const char *outputbase);
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protected:
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virtual bool AddImageHandler(TessBaseAPI* api);
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};
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/**
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* Renders tesseract output into an hocr text string
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*/
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class TESS_API TessHOcrRenderer : public TessResultRenderer {
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public:
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explicit TessHOcrRenderer(const char *outputbase, bool font_info);
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explicit TessHOcrRenderer(const char *outputbase);
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protected:
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virtual bool BeginDocumentHandler();
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virtual bool AddImageHandler(TessBaseAPI* api);
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virtual bool EndDocumentHandler();
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private:
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bool font_info_; // whether to print font information
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};
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/**
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* Renders tesseract output into searchable PDF
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*/
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class TESS_API TessPDFRenderer : public TessResultRenderer {
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public:
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// datadir is the location of the TESSDATA. We need it because
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// we load a custom PDF font from this location.
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TessPDFRenderer(const char *outputbase, const char *datadir);
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protected:
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virtual bool BeginDocumentHandler();
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virtual bool AddImageHandler(TessBaseAPI* api);
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virtual bool EndDocumentHandler();
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private:
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// We don't want to have every image in memory at once,
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// so we store some metadata as we go along producing
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// PDFs one page at a time. At the end that metadata is
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// used to make everything that isn't easily handled in a
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// streaming fashion.
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long int obj_; // counter for PDF objects
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GenericVector<long int> offsets_; // offset of every PDF object in bytes
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GenericVector<long int> pages_; // object number for every /Page object
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const char *datadir_; // where to find the custom font
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// Bookkeeping only. DIY = Do It Yourself.
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void AppendPDFObjectDIY(size_t objectsize);
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// Bookkeeping + emit data.
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void AppendPDFObject(const char *data);
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// Create the /Contents object for an entire page.
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static char* GetPDFTextObjects(TessBaseAPI* api,
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double width, double height);
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// Turn an image into a PDF object. Only transcode if we have to.
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static bool imageToPDFObj(tesseract::TessBaseAPI *api, Pix *pix,
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char *filename, long int objnum, char **pdf_object,
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long int *pdf_object_size);
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};
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/**
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* Renders tesseract output into a plain UTF-8 text string
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*/
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class TESS_API TessUnlvRenderer : public TessResultRenderer {
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public:
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explicit TessUnlvRenderer(const char *outputbase);
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protected:
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virtual bool AddImageHandler(TessBaseAPI* api);
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};
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/**
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* Renders tesseract output into a plain UTF-8 text string
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*/
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class TESS_API TessBoxTextRenderer : public TessResultRenderer {
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public:
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explicit TessBoxTextRenderer(const char *outputbase);
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protected:
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virtual bool AddImageHandler(TessBaseAPI* api);
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};
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} // namespace tesseract.
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#endif // TESSERACT_API_RENDERER_H__
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