CCITTFaxFilter.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.pdfbox.filter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PushbackInputStream;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.io.IOUtils;
/**
* Decodes image data that has been encoded using either Group 3 or Group 4
* CCITT facsimile (fax) encoding, and encodes image data to Group 4.
*
* @author Ben Litchfield
* @author Marcel Kammer
* @author Paul King
*/
final class CCITTFaxFilter extends Filter
{
@Override
public DecodeResult decode(InputStream encoded, OutputStream decoded,
COSDictionary parameters, int index) throws IOException
{
// get decode parameters
COSDictionary decodeParms = getDecodeParams(parameters, index);
// parse dimensions
int cols = decodeParms.getInt(COSName.COLUMNS, 1728);
int rows = decodeParms.getInt(COSName.ROWS, 0);
int height = parameters.getInt(COSName.HEIGHT, COSName.H, 0);
if (rows > 0 && height > 0)
{
// PDFBOX-771, PDFBOX-3727: rows in DecodeParms sometimes contains an incorrect value
rows = height;
}
else
{
// at least one of the values has to have a valid value
rows = Math.max(rows, height);
}
// decompress data
int k = decodeParms.getInt(COSName.K, 0);
boolean encodedByteAlign = decodeParms.getBoolean(COSName.ENCODED_BYTE_ALIGN, false);
int arraySize = (cols + 7) / 8 * rows;
// TODO possible options??
byte[] decompressed = new byte[arraySize];
CCITTFaxDecoderStream s;
int type;
long tiffOptions = 0;
if (k == 0)
{
type = TIFFExtension.COMPRESSION_CCITT_T4; // Group 3 1D
byte[] streamData = new byte[20];
int bytesRead = encoded.read(streamData);
PushbackInputStream pushbackInputStream = new PushbackInputStream(encoded, streamData.length);
pushbackInputStream.unread(streamData, 0, bytesRead);
encoded = pushbackInputStream;
if (streamData[0] != 0 || (streamData[1] >> 4 != 1 && streamData[1] != 1))
{
// leading EOL (0b000000000001) not found, search further and try RLE if not
// found
type = TIFFExtension.COMPRESSION_CCITT_MODIFIED_HUFFMAN_RLE;
short b = (short) (((streamData[0] << 8) + (streamData[1] & 0xff)) >> 4);
for (int i = 12; i < bytesRead * 8; i++)
{
b = (short) ((b << 1) + ((streamData[(i / 8)] >> (7 - (i % 8))) & 0x01));
if ((b & 0xFFF) == 1)
{
type = TIFFExtension.COMPRESSION_CCITT_T4;
break;
}
}
}
}
else if (k > 0)
{
// Group 3 2D
type = TIFFExtension.COMPRESSION_CCITT_T4;
tiffOptions = TIFFExtension.GROUP3OPT_2DENCODING;
}
else
{
// Group 4
type = TIFFExtension.COMPRESSION_CCITT_T6;
}
s = new CCITTFaxDecoderStream(encoded, cols, type, tiffOptions, encodedByteAlign);
readFromDecoderStream(s, decompressed);
// invert bitmap
boolean blackIsOne = decodeParms.getBoolean(COSName.BLACK_IS_1, false);
if (!blackIsOne)
{
// Inverting the bitmap
// Note the previous approach with starting from an IndexColorModel didn't work
// reliably. In some cases the image wouldn't be painted for some reason.
// So a safe but slower approach was taken.
invertBitmap(decompressed);
}
decoded.write(decompressed);
return new DecodeResult(parameters);
}
void readFromDecoderStream(CCITTFaxDecoderStream decoderStream, byte[] result)
throws IOException
{
int pos = 0;
int read;
while ((read = decoderStream.read(result, pos, result.length - pos)) > -1)
{
pos += read;
if (pos >= result.length)
{
break;
}
}
}
private void invertBitmap(byte[] bufferData)
{
for (int i = 0, c = bufferData.length; i < c; i++)
{
bufferData[i] = (byte) (~bufferData[i] & 0xFF);
}
}
@Override
protected void encode(InputStream input, OutputStream encoded, COSDictionary parameters)
throws IOException
{
int cols = parameters.getInt(COSName.COLUMNS);
int rows = parameters.getInt(COSName.ROWS);
CCITTFaxEncoderStream ccittFaxEncoderStream =
new CCITTFaxEncoderStream(encoded, cols, rows, TIFFExtension.FILL_LEFT_TO_RIGHT);
IOUtils.copy(input, ccittFaxEncoderStream);
}
}