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/*
* $Id$
* Copyright (C) 2001 The Apache Software Foundation. All rights reserved.
* For details on use and redistribution please refer to the
* LICENSE file included with these sources.
*/
package org.apache.fop.image.analyser;
// Java
import java.io.BufferedInputStream;
import java.io.IOException;
import org.apache.fop.image.FopImage;
import org.apache.fop.fo.FOUserAgent;
/**
* ImageReader object for JPEG image type.
* @author Pankaj Narula
* @version 1.0
*/
public class JPEGReader implements ImageReader {
/**
* Only SOFn and APPn markers are defined as SOFn is needed for the height and
* width search. APPn is also defined because if the JPEG contains thumbnails
* the dimensions of the thumnail would also be after the SOFn marker enclosed
* inside the APPn marker. And we don't want to confuse those dimensions with
* the image dimensions.
*/
static protected final int MARK = 0xff; // Beginneing of a Marker
static protected final int NULL = 0x00; // Special case for 0xff00
static protected final int SOF1 = 0xc0; // Baseline DCT
static protected final int SOF2 = 0xc1; // Extended Sequential DCT
static protected final int SOF3 = 0xc2; // Progrssive DCT only PDF 1.3
static protected final int SOFA = 0xca; // Progressice DCT only PDF 1.3
static protected final int APP0 = 0xe0; // Application marker, JFIF
static protected final int APPF = 0xef; // Application marker
static protected final int SOS = 0xda; // Start of Scan
static protected final int SOI = 0xd8; // start of Image
static protected final int JPG_SIG_LENGTH = 2;
public FopImage.ImageInfo verifySignature(String uri, BufferedInputStream fis,
FOUserAgent ua) throws IOException {
byte[] header = getDefaultHeader(fis);
boolean supported = ((header[0] == (byte) 0xff) &&
(header[1] == (byte) 0xd8));
if (supported) {
FopImage.ImageInfo info = getDimension(fis);
info.mimeType = getMimeType();
return info;
} else {
return null;
}
}
public String getMimeType() {
return "image/jpeg";
}
protected byte[] getDefaultHeader(BufferedInputStream imageStream) throws IOException {
byte[] header = new byte[JPG_SIG_LENGTH];
try {
imageStream.mark(JPG_SIG_LENGTH + 1);
imageStream.read(header);
imageStream.reset();
} catch (IOException ex) {
try {
imageStream.reset();
} catch (IOException exbis) {}
throw ex;
}
return header;
}
protected FopImage.ImageInfo getDimension(BufferedInputStream imageStream) throws IOException {
FopImage.ImageInfo info = new FopImage.ImageInfo();
try {
int marker = NULL;
long length, skipped;
outer:
while (imageStream.available() > 0) {
while ((marker = imageStream.read()) != MARK) {
;
}
do {
marker = imageStream.read();
} while (marker == MARK)
;
switch (marker) {
case SOI:
break;
case NULL:
break;
case SOF1:
case SOF2:
case SOF3: // SOF3 and SOFA are only supported by PDF 1.3
case SOFA:
this.skip(imageStream, 3);
info.height = this.read2bytes(imageStream);
info.width = this.read2bytes(imageStream);
break outer;
default:
length = this.read2bytes(imageStream);
skipped = this.skip(imageStream, length - 2);
if (skipped != length - 2)
throw new IOException("Skipping Error");
}
}
} catch (IOException ioe) {
try {
imageStream.reset();
} catch (IOException exbis) {}
throw ioe;
}
return info;
}
protected int read2bytes(BufferedInputStream imageStream) throws IOException {
int byte1 = imageStream.read();
int byte2 = imageStream.read();
return (int)((byte1 << 8) | byte2);
}
protected long skip(BufferedInputStream imageStream, long n) throws IOException {
long discarded = 0;
while (discarded != n) {
imageStream.read();
discarded++;
}
return discarded; // scope for exception
}
}
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