special/identify_ocr
Classify the pages in a document based on the page content.
Download Java Code Show Output Show Input (FontReporter_ocr.pdf)
/*
* Classify the pages in a document according to the following criteria:
*
* - No text and raster: The page contains neither text nor raster images, i.e.
* it is empty or contains only vector graphics
* - Image only (raw scan): The page contains at least one image, but not any
* text
* - Searchable image (also called image+hidden text): The page contains at
* least one image plus text with textrendering=TET.TR_INVISIBLE. No other
* text is present on the page.
* - Visible text: The page contains text, and all text uses
* textrendering different from TET.TR_INVISIBLE (=3)
* - Mixed: all other cases, i.e. mixed textrendering modes
*
* Required software: TET 5
*
* Required data: PDF document
*
*/
package com.pdflib.cookbook.tet.special;
import com.pdflib.TET;
import com.pdflib.TETException;
class identify_ocr {
/*
* Global option list. The program expects the "resource" directory parallel to
* the "java" directory.
*/
private static final String GLOBAL_OPTLIST = "searchpath={../resource/cmap " + "../resource/glyphlist ../input}";
/*
* Document specific option list.
*/
private static final String DOC_OPTLIST = "";
/*
* Page-specific option list.
*/
private static final String PAGE_OPTLIST = "granularity=glyph";
/*
* The name of the input file
*/
private String filename;
/*
* Process a page in the document, and print out the classification of the page.
*
* @param tet TET object
* @param doc TET document handle
* @param pageno Page to process
*
* @throws TETException An error occurred in the TET API
*/
private static void process_page(TET tet, final int doc, int pageno) throws TETException {
final int page = tet.open_page(doc, pageno, PAGE_OPTLIST);
if (page == -1) {
System.err.println("Error " + tet.get_errnum() + " in " + tet.get_apiname() + "(): " + tet.get_errmsg());
} else {
// Is invisible text present?
boolean hasInvisibleText = false;
// Is normal text present?
boolean hasNormalText = false;
/* Retrieve all text fragments for the page */
for (String text = tet.get_text(page); text != null; text = tet.get_text(page)) {
/* loop over all characters */
while (tet.get_char_info(page) != -1) {
if (tet.textrendering == TET.TR_INVISIBLE) {
hasInvisibleText = true;
} else {
hasNormalText = true;
}
}
}
/* Check whether there's at least one raster image on the page */
boolean hasImage = false;
if (tet.get_errnum() == 0) {
hasImage = tet.get_image_info(page) == 1;
}
if (tet.get_errnum() == 0) {
boolean hasText = hasInvisibleText || hasNormalText;
System.out.print("Page " + pageno + ": ");
if (hasText) {
if (hasImage && hasInvisibleText && !hasNormalText) {
System.out.print("Searchable image");
} else if (hasNormalText && !hasInvisibleText) {
System.out.print("Visible text");
} else {
System.out.print("Mixed");
}
} else {
// no text at all
if (hasImage) {
System.out.print("Image only");
} else {
System.out.print("No text or raster graphics");
}
}
System.out.println();
} else {
System.err
.println("Error " + tet.get_errnum() + " in " + tet.get_apiname() + "(): " + tet.get_errmsg());
}
tet.close_page(page);
}
}
private void execute() {
TET tet = null;
int pageno = 0;
try {
tet = new TET();
tet.set_option(GLOBAL_OPTLIST);
final int doc = tet.open_document(filename, DOC_OPTLIST);
if (doc == -1) {
System.err
.println("Error " + tet.get_errnum() + " in " + tet.get_apiname() + "(): " + tet.get_errmsg());
return;
}
System.out.println("Page classification for document \"" + filename + "\"");
/*
* Loop over pages in the document
*/
final int n_pages = (int) tet.pcos_get_number(doc, "length:pages");
for (pageno = 1; pageno <= n_pages; ++pageno) {
process_page(tet, doc, pageno);
}
tet.close_document(doc);
} catch (TETException e) {
if (pageno == 0) {
System.err
.println("Error " + e.get_errnum() + " in " + e.get_apiname() + "(): " + e.get_errmsg() + "\n");
} else {
System.err.println("Error " + e.get_errnum() + " in " + e.get_apiname() + "() on page " + pageno + ": "
+ e.get_errmsg() + "\n");
}
System.exit(1);
} finally {
tet.delete();
}
}
/*
* @param filename the name of the file for which the template will be generated
*/
private identify_ocr(String filename) {
this.filename = filename;
}
public static void main(String[] args) {
if (args.length != 1) {
System.out.println("usage: identify_ocr <infilename>");
return;
}
identify_ocr t = new identify_ocr(args[0]);
t.execute();
}
}