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Add PAGE XML renderer / export (#4214)
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Add PAGE XML export and documentation.
To generate PAGE XML output just add 'page' to the tesseract command.

The output is outputname + '.page.xml' to avoid conflicts with ALTO export.

The output can be customized with the flags:
tessedit_create_page_polygon and tessedit_create_page_wordlevel.

Co-authored-by: Stefan Weil <[email protected]>
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JKamlah and stweil committed Apr 19, 2024
1 parent bae520e commit 577e8a8
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Showing 13 changed files with 1,220 additions and 2 deletions.
2 changes: 2 additions & 0 deletions CMakeLists.txt
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Expand Up @@ -740,6 +740,7 @@ set(TESSERACT_SRC
src/api/capi.cpp
src/api/renderer.cpp
src/api/altorenderer.cpp
src/api/pagerenderer.cpp
src/api/hocrrenderer.cpp
src/api/lstmboxrenderer.cpp
src/api/pdfrenderer.cpp
Expand All @@ -764,6 +765,7 @@ set(TESSERACT_CONFIGS
tessdata/configs/lstmbox
tessdata/configs/lstmdebug
tessdata/configs/makebox
tessdata/configs/page
tessdata/configs/pdf
tessdata/configs/quiet
tessdata/configs/rebox
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1 change: 1 addition & 0 deletions Makefile.am
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Expand Up @@ -113,6 +113,7 @@ libtesseract_la_LDFLAGS += -version-info $(GENERIC_LIBRARY_VERSION)

libtesseract_la_SOURCES = src/api/baseapi.cpp
libtesseract_la_SOURCES += src/api/altorenderer.cpp
libtesseract_la_SOURCES += src/api/pagerenderer.cpp
libtesseract_la_SOURCES += src/api/capi.cpp
libtesseract_la_SOURCES += src/api/hocrrenderer.cpp
libtesseract_la_SOURCES += src/api/lstmboxrenderer.cpp
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2 changes: 1 addition & 1 deletion README.md
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Expand Up @@ -36,7 +36,7 @@ Tesseract has **unicode (UTF-8) support**, and can **recognize [more than 100 la

Tesseract supports **[various image formats](https://tesseract-ocr.github.io/tessdoc/InputFormats)** including PNG, JPEG and TIFF.

Tesseract supports **various output formats**: plain text, hOCR (HTML), PDF, invisible-text-only PDF, TSV and ALTO.
Tesseract supports **various output formats**: plain text, hOCR (HTML), PDF, invisible-text-only PDF, TSV, ALTO and PAGE.

You should note that in many cases, in order to get better OCR results, you'll need to **[improve the quality](https://tesseract-ocr.github.io/tessdoc/ImproveQuality.html) of the image** you are giving Tesseract.

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4 changes: 4 additions & 0 deletions doc/tesseract.1.asc
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Expand Up @@ -104,6 +104,10 @@ OPTIONS

* *alto* -- Output in ALTO format ('OUTPUTBASE'`.xml`).
* *hocr* -- Output in hOCR format ('OUTPUTBASE'`.hocr`).
* *page* -- Output in PAGE format ('OUTPUTBASE'`.page.xml`).
The output can be customized with the flags:
page_xml_polygon -- Create polygons instead of bounding boxes (default: true)
page_xml_level -- Create the PAGE file on 0=linelevel or 1=wordlevel (default: 0)
* *pdf* -- Output PDF ('OUTPUTBASE'`.pdf`).
* *tsv* -- Output TSV ('OUTPUTBASE'`.tsv`).
* *txt* -- Output plain text ('OUTPUTBASE'`.txt`).
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12 changes: 12 additions & 0 deletions include/tesseract/baseapi.h
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Expand Up @@ -550,6 +550,18 @@ class TESS_API TessBaseAPI {
*/
char *GetAltoText(int page_number);

/**
* Make an XML-formatted string with PAGE markup from the internal
* data structures.
*/
char *GetPAGEText(ETEXT_DESC *monitor, int page_number);

/**
* Make an XML-formatted string with PAGE markup from the internal
* data structures.
*/
char *GetPAGEText(int page_number);

/**
* Make a TSV-formatted string from the internal data structures.
* page_number is 0-based but will appear in the output as 1-based.
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17 changes: 17 additions & 0 deletions include/tesseract/renderer.h
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Expand Up @@ -198,6 +198,23 @@ class TESS_API TessAltoRenderer : public TessResultRenderer {
bool begin_document;
};

/**
* Renders Tesseract output into a PAGE XML text string
*/
class TESS_API TessPAGERenderer : public TessResultRenderer {
public:
explicit TessPAGERenderer(const char *outputbase);

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

private:
bool begin_document;
};


/**
* Renders Tesseract output into a TSV string
*/
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8 changes: 8 additions & 0 deletions src/api/capi.cpp
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Expand Up @@ -68,6 +68,10 @@ TessResultRenderer *TessAltoRendererCreate(const char *outputbase) {
return new tesseract::TessAltoRenderer(outputbase);
}

TessResultRenderer *TessPAGERendererCreate(const char *outputbase) {
return new tesseract::TessPAGERenderer(outputbase);
}

TessResultRenderer *TessTsvRendererCreate(const char *outputbase) {
return new tesseract::TessTsvRenderer(outputbase);
}
Expand Down Expand Up @@ -420,6 +424,10 @@ char *TessBaseAPIGetAltoText(TessBaseAPI *handle, int page_number) {
return handle->GetAltoText(page_number);
}

char *TessBaseAPIGetPAGEText(TessBaseAPI *handle, int page_number) {
return handle->GetPAGEText(page_number);
}

char *TessBaseAPIGetTsvText(TessBaseAPI *handle, int page_number) {
return handle->GetTSVText(page_number);
}
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2 comments on commit 577e8a8

@nguyenq
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Does capi.h need update as well?

@stweil
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@stweil stweil commented on 577e8a8 Apr 24, 2024

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Yes, that's still missing. Thank you for your hint.

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