identify_ocr
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=3 (invisible). No other text is present on the page.
Visible text: The page contains text, and all text uses textrendering!=3
Mixed: all other cases, i.e. mixed textrendering modes
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import com.pdflib.TET;
import com.pdflib.TETException;
/**
* Classify the pages in a document according to the following criteria:
* <p>
* - No text and raster: The page contains neither text nor raster images, i.e.
* it is empty or contains only vector graphics<br>
* - Image only (raw scan): The page contains at least one image, but not any
* text<br>
* - Searchable image (also called image+hidden text): The page contains at
* least one image plus text with textrendering=3 (invisible). No other text is
* present on the page.<br>
* - Visible text: The page contains text, and all text uses textrendering!=3<br>
* - Mixed: all other cases, i.e. mixed textrendering modes<br>
* <p>
* Required software: TET 3
* <p>
* Required data: PDF document
*
* @version $Id: identify_ocr.java,v 1.2 2008/11/21 07:37:42 stm Exp $
*/
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;
/**
* Invisible text rendering mode.
*/
private static final int INVISIBLE_TEXT_RENDERING = 3;
/**
* 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 == INVISIBLE_TEXT_RENDERING) {
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");
}
}
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();
}
}