/*
* $RCSfile: PNMCodec.java,v $
*
* Copyright (c) 2005 Sun Microsystems, Inc. All rights reserved.
*
* Use is subject to license terms.
*
* $Revision: 1.1 $
* $Date: 2005/02/11 04:55:38 $
* $State: Exp $
*/
package com.sun.media.jai.codecimpl;
import java.awt.image.DataBuffer;
import java.awt.image.RenderedImage;
import java.awt.image.SampleModel;
import java.io.BufferedInputStream;
import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;
import com.sun.media.jai.codec.ForwardSeekableStream;
import com.sun.media.jai.codec.ImageCodec;
import com.sun.media.jai.codec.ImageDecoder;
import com.sun.media.jai.codec.ImageDecodeParam;
import com.sun.media.jai.codec.ImageEncoder;
import com.sun.media.jai.codec.ImageEncodeParam;
import com.sun.media.jai.codec.PNMEncodeParam;
import com.sun.media.jai.codec.SeekableStream;
/**
* A subclass of <code>ImageCodec</code> that handles the
* PNM family of formats (PBM, PGM, PPM).
*
* <p> The PBM format encodes a single-banded, 1-bit image. The PGM
* format encodes a single-banded image of any bit depth between 1 and
* 32. The PPM format encodes three-banded images of any bit depth
* between 1 and 32. All formats have an ASCII and a raw
* representation.
*
* @since EA2
*/
public final class PNMCodec extends ImageCodec {
/** Constructs an instance of <code>PNMCodec</code>. */
public PNMCodec() {}
/** Returns the name of the format handled by this codec. */
public String getFormatName() {
return "pnm";
}
public Class getEncodeParamClass() {
return com.sun.media.jai.codec.PNMEncodeParam.class;
}
public Class getDecodeParamClass() {
return Object.class;
}
public boolean canEncodeImage(RenderedImage im,
ImageEncodeParam param) {
SampleModel sampleModel = im.getSampleModel();
int dataType = sampleModel.getTransferType();
if ((dataType == DataBuffer.TYPE_FLOAT) ||
(dataType == DataBuffer.TYPE_DOUBLE)) {
return false;
}
int numBands = sampleModel.getNumBands();
if (numBands != 1 && numBands != 3) {
return false;
}
return true;
}
/**
* Instantiates a <code>PNMImageEncoder</code> to write to the
* given <code>OutputStream</code>.
*
* @param dst the <code>OutputStream</code> to write to.
* @param param an instance of <code>PNMEncodeParam</code> used to
* control the encoding process, or <code>null</code>. A
* <code>ClassCastException</code> will be thrown if
* <code>param</code> is non-null but not an instance of
* <code>PNMEncodeParam</code>.
*/
protected ImageEncoder createImageEncoder(OutputStream dst,
ImageEncodeParam param) {
PNMEncodeParam p = null;
if (param != null) {
p = (PNMEncodeParam)param; // May throw a ClassCast exception
}
return new PNMImageEncoder(dst, p);
}
/**
* Instantiates a <code>PNMImageDecoder</code> to read from the
* given <code>InputStream</code>.
*
* <p> By overriding this method, <code>PNMCodec</code> is able to
* ensure that a <code>ForwardSeekableStream</code> is used to
* wrap the source <code>InputStream</code> instead of the a
* general (and more expensive) subclass of
* <code>SeekableStream</code>. Since the PNM decoder does not
* require the ability to seek backwards in its input, this allows
* for greater efficiency.
*
* @param src the <code>InputStream</code> to read from.
* @param param an instance of <code>ImageDecodeParam</code> used to
* control the decoding process, or <code>null</code>.
* This parameter is ignored by this class.
*/
protected ImageDecoder createImageDecoder(InputStream src,
ImageDecodeParam param) {
// Add buffering for efficiency
if (!(src instanceof BufferedInputStream)) {
src = new BufferedInputStream(src);
}
return new PNMImageDecoder(new ForwardSeekableStream(src), null);
}
/**
* Instantiates a <code>PNMImageDecoder</code> to read from the
* given <code>SeekableStream</code>.
*
* @param src the <code>SeekableStream</code> to read from.
* @param param an instance of <code>ImageDecodeParam</code> used to
* control the decoding process, or <code>null</code>.
* This parameter is ignored by this class.
*/
protected ImageDecoder createImageDecoder(SeekableStream src,
ImageDecodeParam param) {
return new PNMImageDecoder(src, null);
}
/**
* Returns the number of bytes from the beginning of the data required
* to recognize it as being in PNM format.
*/
public int getNumHeaderBytes() {
return 2;
}
/**
* Returns <code>true</code> if the header bytes indicate PNM format.
*
* @param header an array of bytes containing the initial bytes of the
* input data. */
public boolean isFormatRecognized(byte[] header) {
return ((header[0] == 'P') &&
(header[1] >= '1') &&
(header[1] <= '6'));
}
}