us.zuercher.gpx2map.image.netpbm
Class PpmImage

java.lang.Object
  us.zuercher.gpx2map.image.netpbm.AbstractNetpbmImage
      us.zuercher.gpx2map.image.netpbm.PpmImage

All Implemented Interfaces:

Image, NetpbmImage

public class PpmImage
extends AbstractNetpbmImage

PpmImage is a read-only representation of a PPM image. It supports reading both 1- and 2-byte pixel color values, but only the binary PPM format. Images are converted to "maxval 255" as part of loading.

Author:

Stephan Zuercher

Field Summary

private static int	DEPTH PPM depth is always 3.
static String	NETPBM_PPM_MAGIC_NUMBER Magic number for a Netpbm PPM image.
private int[][]	rasterLine Pixelized raster line.
private byte[]	rasterLineData Buffer space for a single raster-line of the image.

Fields inherited from class us.zuercher.gpx2map.image.netpbm.AbstractNetpbmImage

header, height, input, width

Constructor Summary

PpmImage(InputStream input)
Constructs a new PpmImage from the given InputStream.

Method Summary

int	getDepth() PPM images are always depth 3.
int[][]	getNextRasterLine() Reads the next raster from the PPM file.
boolean	hasAlphaChannel() PPM images do not contain alpha-channel information.
protected void	readHeader() Reads the image's header block.

Methods inherited from class us.zuercher.gpx2map.image.netpbm.AbstractNetpbmImage

adjustToMaxVal255, close, getHeader, getHeight, getMaxVal, getOriginalBytesPerPixelPerColor, getRaster, getWidth, readWord, setOriginalMaxVal, skipWS

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

NETPBM_PPM_MAGIC_NUMBER

public static final String NETPBM_PPM_MAGIC_NUMBER

Magic number for a Netpbm PPM image.

See Also:

Constant Field Values

DEPTH

private static final int DEPTH

PPM depth is always 3.

See Also:

Constant Field Values

rasterLineData

private byte[] rasterLineData

Buffer space for a single raster-line of the image. This is the image width multiplied by DEPTH, multiplied by the number of bytes per pixel color (1 or 2).

rasterLine

private int[][] rasterLine

Pixelized raster line. Size is int[width][DEPTH].

Constructor Detail

PpmImage

PpmImage(InputStream input)

Constructs a new PpmImage from the given InputStream.

Parameters:

input - the input stream

Method Detail

hasAlphaChannel

public boolean hasAlphaChannel()

PPM images do not contain alpha-channel information.

Returns:

always returns false.

getDepth

public int getDepth()

PPM images are always depth 3.

Returns:

raster depth

getNextRasterLine

public int[][] getNextRasterLine()
                          throws IOException

Reads the next raster from the PPM file. Note that the array returned by this method is re-used for each subsequent call to this method. If you need to keep a copy of the raster beyond the next call to this method, make a copy of it.

Returns:

next raster or null if EOF

Throws:

IOException - on file error

readHeader

protected void readHeader()
                   throws IOException

Reads the image's header block.

Specified by:

readHeader in class AbstractNetpbmImage

Throws:

IOException - if the image head cannot be read or is invalid