com.gemalto.jp2

Class JP2Decoder

java.lang.Object

com.gemalto.jp2.JP2Decoder

public class JP2Decoder
extends java.lang.Object

JPEG-2000 bitmap decoder. The supported data formats are: JP2 (standard JPEG-2000 file format) and J2K (JPEG-2000 codestream). Only RGB(A) and grayscale(A) colorspaces are supported.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	JP2Decoder.Header

Constructor Summary

Constructors

Constructor and Description
JP2Decoder(byte[] data) Decode a JPEG-2000 image from a byte array.
JP2Decoder(java.io.InputStream is) Decode a JPEG-2000 image from a stream.
JP2Decoder(java.lang.String fileName) Decode a JPEG-2000 image file.

Method Summary

Modifier and Type	Method and Description
android.graphics.Bitmap	decode()
JP2Decoder	disableBitmapPremultiplication() This allows you to turn off alpha pre-multiplication in the output bitmap.
static boolean	isJPEG2000(byte[] data) Returns true if the byte array starts with values typical for a JPEG-2000 header.
JP2Decoder.Header	readHeader() Decodes the file header information and returns it in a JP2Decoder.Header object.
JP2Decoder	setLayersToDecode(int layersToDecode) Set the maximum number of quality layers to decode.
JP2Decoder	setSkipResolutions(int skipResolutions) Set the number of highest resolution levels to be discarded.

Methods inherited from class java.lang.Object

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

Constructor Detail

JP2Decoder

public JP2Decoder(byte[] data)

Decode a JPEG-2000 image from a byte array.

Parameters:

data - the JPEG-2000 image

JP2Decoder

public JP2Decoder(java.lang.String fileName)

Decode a JPEG-2000 image file.

Parameters:

fileName - the name of the JPEG-2000 file

JP2Decoder

public JP2Decoder(java.io.InputStream is)

Decode a JPEG-2000 image from a stream.

Parameters:

is - the stream containing the JPEG-2000 image
Note: the whole content of the stream will be read. The end of image data is not detected.

Method Detail

setSkipResolutions

public JP2Decoder setSkipResolutions(int skipResolutions)

Set the number of highest resolution levels to be discarded. The image resolution is effectively divided by 2 to the power of the number of discarded levels. The reduce factor is limited by the number of stored resolutions in the file. The number of existing resolutions can be detected using the readHeader() method.

At least one (the lowest) resolution is always decoded, no matter how high a number you set here.

Default value: 0 (the image is decoded up to the highest resolution)

Parameters:

skipResolutions - the number of resolutions to skip

Returns:

this instance of JP2Decoder

setLayersToDecode

public JP2Decoder setLayersToDecode(int layersToDecode)

Set the maximum number of quality layers to decode. If there are less quality layers than the specified number, all the quality layers are decoded. The available number of quality layers can be detected using the readHeader() method. Special value 0 indicates all layers.

Default value: 0 (all layers are decoded)

Parameters:

layersToDecode - number of quality layers to decode

Returns:

this instance of JP2Decoder

disableBitmapPremultiplication

public JP2Decoder disableBitmapPremultiplication()

This allows you to turn off alpha pre-multiplication in the output bitmap. Normally Android bitmaps with alpha channel have their RGB component pre-multiplied by the normalized alpha channel. This improves performance when displaying the bitmap, but it leads to loss of precision. This is no problem when you only want to display the bitmap, but it can be a problem when you want to further process the bitmap's raw data.

Since API 19 you can turn this pre-multiplication off. The loss of precision doesn't occur then, but the system wont't be able to draw the output bitmap. On API < 19 this setting is ignored.

In most cases you should not use this.

Returns:

this instance of JP2Decoder

See Also:

Bitmap.setPremultiplied(boolean), BitmapFactory.Options#inPremultiplied

isJPEG2000

public static boolean isJPEG2000(byte[] data)

Returns true if the byte array starts with values typical for a JPEG-2000 header.

Parameters:

data - the byte array to check

Returns:

true if the beginning looks like a JPEG-2000 header; false otherwise

decode

public android.graphics.Bitmap decode()

Returns:

the decoded image; null in case of an error

readHeader

public JP2Decoder.Header readHeader()

Decodes the file header information and returns it in a JP2Decoder.Header object.

Returns:

file header information