de.matthiasmann.twl.utils

Class PNGDecoder

java.lang.Object

de.matthiasmann.twl.utils.PNGDecoder

public class PNGDecoder
extends Object

A PNGDecoder. The slick PNG decoder is based on this class :)

Author:

Matthias Mann

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PNGDecoder.Format

Constructor Summary

Constructors

Constructor and Description
PNGDecoder(InputStream input)

Method Summary

Methods

Modifier and Type	Method and Description
PNGDecoder.Format	decideTextureFormat(PNGDecoder.Format fmt) Computes the implemented format conversion for the desired format.
void	decode(ByteBuffer buffer, int stride, PNGDecoder.Format fmt) Decodes the image into the specified buffer.
void	decodeFlipped(ByteBuffer buffer, int stride, PNGDecoder.Format fmt) Decodes the image into the specified buffer.
int	getHeight()
int	getWidth()
boolean	hasAlpha() Checks if the image has transparency information either from an alpha channel or from a tRNS chunk.
boolean	hasAlphaChannel() Checks if the image has a real alpha channel.
boolean	isRGB()
void	overwriteTRNS(byte r, byte g, byte b) Overwrites the tRNS chunk entry to make a selected color transparent.

Methods inherited from class java.lang.Object

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

Constructor Detail

PNGDecoder

public PNGDecoder(InputStream input)
           throws IOException

Throws:

IOException

Method Detail

getHeight

public int getHeight()

getWidth

public int getWidth()

hasAlphaChannel

public boolean hasAlphaChannel()

Checks if the image has a real alpha channel. This method does not check for the presence of a tRNS chunk.

Returns:

true if the image has an alpha channel

See Also:

hasAlpha()

hasAlpha

public boolean hasAlpha()

Checks if the image has transparency information either from an alpha channel or from a tRNS chunk.

Returns:

true if the image has transparency

See Also:

hasAlphaChannel(), overwriteTRNS(byte, byte, byte)

isRGB

public boolean isRGB()

overwriteTRNS

public void overwriteTRNS(byte r,
                 byte g,
                 byte b)

Overwrites the tRNS chunk entry to make a selected color transparent.

This can only be invoked when the image has no alpha channel.

Calling this method causes hasAlpha() to return true.

Parameters:

r - the red component of the color to make transparent

g - the green component of the color to make transparent

b - the blue component of the color to make transparent

Throws:

UnsupportedOperationException - if the tRNS chunk data can't be set

See Also:

hasAlphaChannel()

decideTextureFormat

public PNGDecoder.Format decideTextureFormat(PNGDecoder.Format fmt)

Computes the implemented format conversion for the desired format.

Parameters:

fmt - the desired format

Returns:

format which best matches the desired format

Throws:

UnsupportedOperationException - if this PNG file can't be decoded

decode

public void decode(ByteBuffer buffer,
          int stride,
          PNGDecoder.Format fmt)
            throws IOException

Decodes the image into the specified buffer. The first line is placed at the current position. After decode the buffer position is at the end of the last line.

Parameters:

buffer - the buffer

stride - the stride in bytes from start of a line to start of the next line, can be negative.

fmt - the target format into which the image should be decoded.

Throws:

IOException - if a read or data error occurred

IllegalArgumentException - if the start position of a line falls outside the buffer

UnsupportedOperationException - if the image can't be decoded into the desired format

decodeFlipped

public void decodeFlipped(ByteBuffer buffer,
                 int stride,
                 PNGDecoder.Format fmt)
                   throws IOException

Decodes the image into the specified buffer. The last line is placed at the current position. After decode the buffer position is at the end of the first line.

Parameters:

buffer - the buffer

stride - the stride in bytes from start of a line to start of the next line, must be positive.

fmt - the target format into which the image should be decoded.

Throws:

IOException - if a read or data error occurred

IllegalArgumentException - if the start position of a line falls outside the buffer

UnsupportedOperationException - if the image can't be decoded into the desired format