/**
* Copyright @ 2012 Quan Nguyen
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.sismics.tess4j;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.Properties;
import javax.imageio.IIOImage;
import com.sun.jna.Pointer;
/**
* An object layer on top of
* TessAPI, provides character recognition support for common image
* formats, and multi-page TIFF images beyond the uncompressed, binary TIFF
* format supported by Tesseract OCR engine. The extended capabilities are
* provided by the
* Java Advanced Imaging Image I/O Tools.
Support for
* PDF documents is available through
* Ghost4J, a
* JNA wrapper for
* GPL Ghostscript, which should be installed and included in
* system path.
Any program that uses the library will need to
* ensure that the required libraries (the
* .jar files for
* jna,
* jai-imageio, and
* ghost4j) are in its compile and run-time
* classpath.
*/
public class Tesseract {
private static Tesseract instance;
private final static Rectangle EMPTY_RECTANGLE = new Rectangle();
private String language = "eng";
private String datapath = null;
private int psm = TessAPI.TessPageSegMode.PSM_AUTO;
private boolean hocr;
private int pageNum;
private int ocrEngineMode = TessAPI.TessOcrEngineMode.OEM_DEFAULT;
private Properties prop = new Properties();
public final static String htmlBeginTag =
"\n"
+ "\n\n\n"
+ "\n\n"
+ "\n\n";
public final static String htmlEndTag = "\n\n";
/**
* Private constructor.
*/
private Tesseract() {
System.setProperty("jna.encoding", "UTF8");
}
/**
* Gets an instance of the class library.
*
* @return instance
*/
public static synchronized Tesseract getInstance() {
if (instance == null) {
instance = new Tesseract();
}
return instance;
}
/**
* Sets tessdata path.
*
* @param datapath the tessdata path to set
*/
public void setDatapath(String datapath) {
this.datapath = datapath;
}
/**
* Sets language for OCR.
*
* @param language the language code, which follows ISO 639-3 standard.
*/
public void setLanguage(String language) {
this.language = language;
}
/**
* Sets OCR engine mode.
*
* @param ocrEngineMode the OcrEngineMode to set
*/
public void setOcrEngineMode(int ocrEngineMode) {
this.ocrEngineMode = ocrEngineMode;
}
/**
* Sets page segmentation mode.
*
* @param mode the page segmentation mode to set
*/
public void setPageSegMode(int mode) {
this.psm = mode;
}
/**
* Enables hocr output.
*
* @param hocr to enable or disable hocr output
*/
public void setHocr(boolean hocr) {
this.hocr = hocr;
prop.setProperty("tessedit_create_hocr", hocr ? "1" : "0");
}
/**
* Set the value of Tesseract's internal parameter.
*
* @param key variable name, e.g.,
* tessedit_create_hocr,
* tessedit_char_whitelist, etc.
* @param value value for corresponding variable, e.g., "1", "0",
* "0123456789", etc.
*/
public void setTessVariable(String key, String value) {
prop.setProperty(key, value);
}
/**
* Performs OCR operation.
*
* @param bi a buffered image
* @return the recognized text
* @throws TesseractException
*/
public String doOCR(BufferedImage bi) throws TesseractException {
return doOCR(bi, null);
}
/**
* Performs OCR operation.
*
* @param bi a buffered image
* @param rect the bounding rectangle defines the region of the image to be
* recognized. A rectangle of zero dimension or
* null indicates the whole image.
* @return the recognized text
* @throws TesseractException
*/
public String doOCR(BufferedImage bi, Rectangle rect) throws TesseractException {
IIOImage oimage = new IIOImage(bi, null, null);
List imageList = new ArrayList();
imageList.add(oimage);
return doOCR(imageList, rect);
}
/**
* Performs OCR operation.
*
* @param imageList a list of
* IIOImage objects
* @param rect the bounding rectangle defines the region of the image to be
* recognized. A rectangle of zero dimension or
* null indicates the whole image.
* @return the recognized text
* @throws TesseractException
*/
public String doOCR(List imageList, Rectangle rect) throws TesseractException {
StringBuilder sb = new StringBuilder();
pageNum = 0;
for (IIOImage oimage : imageList) {
pageNum++;
try {
ByteBuffer buf = ImageIOHelper.getImageByteBuffer(oimage);
RenderedImage ri = oimage.getRenderedImage();
String pageText = doOCR(ri.getWidth(), ri.getHeight(), buf, rect, ri.getColorModel().getPixelSize());
sb.append(pageText);
} catch (IOException ioe) {
//skip the problematic image
System.err.println(ioe.getMessage());
}
}
if (hocr) {
sb.insert(0, htmlBeginTag).append(htmlEndTag);
}
return sb.toString();
}
/**
* Performs OCR operation. Use
* SetImage, (optionally)
* SetRectangle, and one or more of the
* Get*Text functions.
*
* @param xsize width of image
* @param ysize height of image
* @param buf pixel data
* @param rect the bounding rectangle defines the region of the image to be
* recognized. A rectangle of zero dimension or
* null indicates the whole image.
* @param bpp bits per pixel, represents the bit depth of the image, with 1
* for binary bitmap, 8 for gray, and 24 for color RGB.
* @return the recognized text
* @throws TesseractException
*/
public String doOCR(int xsize, int ysize, ByteBuffer buf, Rectangle rect, int bpp) throws TesseractException {
TessAPI api = TessAPI.INSTANCE;
TessAPI.TessBaseAPI handle = api.TessBaseAPICreate();
api.TessBaseAPIInit2(handle, datapath, language, ocrEngineMode);
api.TessBaseAPISetPageSegMode(handle, psm);
Enumeration em = prop.propertyNames();
while (em.hasMoreElements()) {
String key = (String) em.nextElement();
api.TessBaseAPISetVariable(handle, key, prop.getProperty(key));
}
int bytespp = bpp / 8;
int bytespl = (int) Math.ceil(xsize * bpp / 8.0);
api.TessBaseAPISetImage(handle, buf, xsize, ysize, bytespp, bytespl);
if (rect != null && !rect.equals(EMPTY_RECTANGLE)) {
api.TessBaseAPISetRectangle(handle, rect.x, rect.y, rect.width, rect.height);
}
Pointer utf8Text = hocr ? api.TessBaseAPIGetHOCRText(handle, pageNum - 1) : api.TessBaseAPIGetUTF8Text(handle);
String str = utf8Text.getString(0);
api.TessDeleteText(utf8Text);
api.TessBaseAPIDelete(handle);
return str;
}
}