Class Alto

Namespace

Egami.Ocr

Assembly

Egami.dll

Reads and writes ALTO (Analyzed Layout and Text Object), the XML format of library digitization that ABBYY, Tesseract and Transkribus write: pages (Page), lines (TextLine) and words (String) with their positions, WC confidence and LANG.

public static class Alto

Inheritance

object

Alto

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Examples

// ALTO from ABBYY, Tesseract or a library's digitization: positions in 1/10 mm or 1/1200 inch become pixels at Dpi.
IReadOnlyList<OcrResult> pages = Alto.Parse(File.ReadAllText("page.xml"), new OcrReadOptions { Dpi = 300 });
Console.WriteLine($"{pages[0].ImageSize}: {pages[0].Text}");

// Turn it into hOCR, or write ALTO 4 in pixels.
using FileStream hocr = File.Create("page.hocr");
Hocr.Write(hocr, pages);
using FileStream alto = File.Create("page-v4.xml");
Alto.Write(alto, pages);

Remarks

The reader takes ALTO 1 to 4 by element names, in any namespace. Positions in 1/10 mm or 1/1200 inch become pixels at Dpi. A HYP hyphen joins the word before it. No DTD or schema is ever fetched. The writer writes ALTO 4 in pixels.

Methods

Parse(string, OcrReadOptions?)

Reads every page of ALTO text.

public static IReadOnlyList<OcrResult> Parse(string alto, OcrReadOptions? options = null)

Parameters

alto string

The ALTO document.

options OcrReadOptions

The limits and the resolution for physical units, or null for Default.

Returns

IReadOnlyList<OcrResult>

One result per Page, in document order.

Examples

// ALTO from ABBYY, Tesseract or a library's digitization: positions in 1/10 mm or 1/1200 inch become pixels at Dpi.
IReadOnlyList<OcrResult> pages = Alto.Parse(File.ReadAllText("page.xml"), new OcrReadOptions { Dpi = 300 });
Console.WriteLine($"{pages[0].ImageSize}: {pages[0].Text}");

// Turn it into hOCR, or write ALTO 4 in pixels.
using FileStream hocr = File.Create("page.hocr");
Hocr.Write(hocr, pages);
using FileStream alto = File.Create("page-v4.xml");
Alto.Write(alto, pages);

Exceptions

ArgumentNullException

alto is null.

CorruptDataException

The text is not well-formed XML, or has no alto root element.

LimitExceededException

The text breaks a limit of options.

Read(Stream, OcrReadOptions?)

Reads every page of an ALTO file.

public static IReadOnlyList<OcrResult> Read(Stream stream, OcrReadOptions? options = null)

Parameters

stream Stream

The file, from its current position. It is left open.

options OcrReadOptions

The limits and the resolution for physical units, or null for Default.

Returns

IReadOnlyList<OcrResult>

One result per Page, in file order.

Examples

// ALTO from ABBYY, Tesseract or a library's digitization: positions in 1/10 mm or 1/1200 inch become pixels at Dpi.
IReadOnlyList<OcrResult> pages = Alto.Parse(File.ReadAllText("page.xml"), new OcrReadOptions { Dpi = 300 });
Console.WriteLine($"{pages[0].ImageSize}: {pages[0].Text}");

// Turn it into hOCR, or write ALTO 4 in pixels.
using FileStream hocr = File.Create("page.hocr");
Hocr.Write(hocr, pages);
using FileStream alto = File.Create("page-v4.xml");
Alto.Write(alto, pages);

Exceptions

ArgumentNullException

stream is null.

CorruptDataException

The file is not well-formed XML, or has no alto root element.

LimitExceededException

The file breaks a limit of options.

Write(Stream, IEnumerable<OcrResult>)

Writes pages as an ALTO 4 document in UTF-8, in pixels, one Page per result.

public static void Write(Stream stream, IEnumerable<OcrResult> pages)

Parameters

stream Stream

Where to write, from its current position. It is left open.

pages IEnumerable<OcrResult>

The pages.

Examples

// ALTO from ABBYY, Tesseract or a library's digitization: positions in 1/10 mm or 1/1200 inch become pixels at Dpi.
IReadOnlyList<OcrResult> pages = Alto.Parse(File.ReadAllText("page.xml"), new OcrReadOptions { Dpi = 300 });
Console.WriteLine($"{pages[0].ImageSize}: {pages[0].Text}");

// Turn it into hOCR, or write ALTO 4 in pixels.
using FileStream hocr = File.Create("page.hocr");
Hocr.Write(hocr, pages);
using FileStream alto = File.Create("page-v4.xml");
Alto.Write(alto, pages);

Exceptions

ArgumentNullException

stream or pages is null.