com.gemalto.jp2

Class JP2Encoder

java.lang.Object

com.gemalto.jp2.JP2Encoder

public class JP2Encoder
extends java.lang.Object

JPEG-2000 bitmap encoder. Output properties:

• file format: JP2 (standard JPEG-2000 file format) or J2K (JPEG-2000 codestream)
• colorspace: RGB or RGBA (depending on the hasAlpha() value of the input bitmap)
• precision: 8 bits per channel
• image quality: can be set by visual quality or compression ratio; or lossless

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	JP2Encoder.OutputFormat

Field Summary

Fields

Modifier and Type	Field and Description
static int	FORMAT_J2K JPEG 2000 codestream format
static int	FORMAT_JP2 The standard JPEG-2000 file format

Constructor Summary

Constructors

Constructor and Description
JP2Encoder(android.graphics.Bitmap bmp) Creates a new instance of the JPEG-2000 encoder.

Method Summary

Modifier and Type	Method and Description
byte[]	encode() Encode to JPEG-2000, return the result as a byte array.
int	encode(java.io.OutputStream out) Encode to JPEG-2000, write the result into an OutputStream.
boolean	encode(java.lang.String fileName) Encode to JPEG-2000, store the result into a file.
JP2Encoder	setCompressionRatio(float... compressionRatios) Set compression ratio.
JP2Encoder	setNumResolutions(int numResolutions) Set the number of resolutions.
JP2Encoder	setOutputFormat(int outputFormat) Sets the output file format.
JP2Encoder	setVisualQuality(float... qualityValues) Set image quality.

Methods inherited from class java.lang.Object

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

Field Detail

FORMAT_J2K

public static final int FORMAT_J2K

JPEG 2000 codestream format

See Also:

Constant Field Values

FORMAT_JP2

public static final int FORMAT_JP2

The standard JPEG-2000 file format

See Also:

Constant Field Values

Constructor Detail

JP2Encoder

public JP2Encoder(android.graphics.Bitmap bmp)

Creates a new instance of the JPEG-2000 encoder.

Parameters:

bmp - the bitmap to encode

Method Detail

setNumResolutions

public JP2Encoder setNumResolutions(int numResolutions)

Set the number of resolutions. It corresponds to the number of DWT decompositions +1. Minimum number of resolutions is 1. Maximum is floor(log2(min_image_dimension)) + 1.

Some software might be able to take advantage of this and decode only smaller resolution when appropriate. (This library is one such software. See JP2Decoder.setSkipResolutions(int)).

Default value: 6 if the image dimensions are at least 32x32. Otherwise the maximum supported number of resolutions.

Parameters:

numResolutions - number of resolutions

Returns:

this JP2Encoder instance

setCompressionRatio

public JP2Encoder setCompressionRatio(float... compressionRatios)

Set compression ratio. The value is a factor of compression, thus 20 means 20 times compressed (measured against the raw, uncompressed image size). 1 indicates lossless compression

This option produces a predictable image size, but the visual image quality will depend on how "compressible" the original image is. If you want to get predictable visual quality (but unpredictable size), use setVisualQuality(float...).

You can set multiple compression ratios - this will produce an image with multiple quality layers. Some software might be able to take advantage of this and decode only lesser quality layer when appropriate. (This library is one such software. See JP2Decoder.setLayersToDecode(int).)

Default value: a single lossless quality layer.

Note: setCompressionRatio(float...) and setVisualQuality(float...) cannot be used together.

Parameters:

compressionRatios - compression ratios

Returns:

this JP2Encoder instance

setVisualQuality

public JP2Encoder setVisualQuality(float... qualityValues)

Set image quality. The value is a PSNR, measured in dB. Higher PSNR means higher quality. A special value 0 indicates lossless quality.

As for reasonable values: 20 is extremely aggressive compression, 60-70 is close to lossless. For "normal" compression you might want to aim at 30-50, depending on your needs.

This option produces predictable visual image quality, but the file size will depend on how "compressible" the original image is. If you want to get predictable size (but unpredictable visual quality), use setCompressionRatio(float...).

You can set multiple quality values - this will produce an image with multiple quality layers. Some software might be able to take advantage of this and decode only lesser quality layer when appropriate. (This library is one such software. See JP2Decoder.setLayersToDecode(int).)

Default value: a single lossless quality layer.

Note: setVisualQuality(float...) and setCompressionRatio(float...) cannot be used together.

Parameters:

qualityValues - quality layer PSNR values

Returns:

this JP2Encoder instance

setOutputFormat

public JP2Encoder setOutputFormat(int outputFormat)

Sets the output file format. The default value is FORMAT_JP2.

Parameters:

outputFormat - FORMAT_J2K or FORMAT_JP2

Returns:

this JP2Encoder instance

encode

public byte[] encode()

Encode to JPEG-2000, return the result as a byte array.

Returns:

the JPEG-2000 encoded data

encode

public boolean encode(java.lang.String fileName)

Encode to JPEG-2000, store the result into a file.

Parameters:

fileName - the name of the output file

Returns:

true if the image was successfully converted and stored; false otherwise

encode

public int encode(java.io.OutputStream out)
           throws java.io.IOException

Encode to JPEG-2000, write the result into an OutputStream.

Parameters:

out - the stream into which the result will be written

Returns:

the number of bytes written; 0 in case of a conversion error

Throws:

java.io.IOException - if there's an error writing the result into the output stream