JPEGQTable (Java Platform SE 6)

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javax.imageio.plugins.jpeg
class JPEGQTable

java.lang.Object
  javax.imageio.plugins.jpeg.JPEGQTable

public class JPEGQTable
extends Object

A class encapsulating a single JPEG quantization table. The elements appear in natural order (as opposed to zig-zag order). Static variables are provided for the "standard" tables taken from Annex K of the JPEG spec, as well as the default tables conventionally used for visually lossless encoding.

For more information about the operation of the built-in JPEG plug-ins, see the JPEG metadata format specification and usage notes.

Field Summary
`static JPEGQTable`	`K1Div2Luminance` The sample luminance quantization table given in the JPEG specification, table K.1, with all elements divided by 2.
`static JPEGQTable`	`K1Luminance` The sample luminance quantization table given in the JPEG specification, table K.1.
`static JPEGQTable`	`K2Chrominance` The sample chrominance quantization table given in the JPEG specification, table K.2.
`static JPEGQTable`	`K2Div2Chrominance` The sample chrominance quantization table given in the JPEG specification, table K.2, with all elements divided by 2.

Constructor Summary
`JPEGQTable(int[] table)` Constructs a quantization table from the argument, which must contain 64 elements in natural order (not zig-zag order).

Method Summary
`JPEGQTable`	`getScaledInstance(float scaleFactor, boolean forceBaseline)` Returns a new quantization table where the values are multiplied by `scaleFactor` and then clamped to the range 1..32767 (or to 1..255 if `forceBaseline` is `true`).
`int[]`	`getTable()` Returns a copy of the current quantization table as an array of ints in natural (not zig-zag) order.
`String`	`toString()` Returns a string representation of the object.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

K1Div2Luminance

public static final JPEGQTable K1Div2Luminance

The sample luminance quantization table given in the JPEG specification, table K.1, with all elements divided by 2. According to the specification, these values produce "very good" quality output. This is the table usually used for "visually lossless" encoding, and is the default luminance table used if the default tables and quality settings are used.

K1Luminance

public static final JPEGQTable K1Luminance

The sample luminance quantization table given in the JPEG specification, table K.1. According to the specification, these values produce "good" quality output.

K2Chrominance

public static final JPEGQTable K2Chrominance

The sample chrominance quantization table given in the JPEG specification, table K.2. According to the specification, these values produce "good" quality output.

K2Div2Chrominance

public static final JPEGQTable K2Div2Chrominance

The sample chrominance quantization table given in the JPEG specification, table K.2, with all elements divided by 2. According to the specification, these values produce "very good" quality output. This is the table usually used for "visually lossless" encoding, and is the default chrominance table used if the default tables and quality settings are used.

Constructor Detail

JPEGQTable

public JPEGQTable(int[] table)

Constructs a quantization table from the argument, which must contain 64 elements in natural order (not zig-zag order). A copy is made of the the input array.

Parameters:: table - the quantization table, as an int array.

Method Detail

getScaledInstance

public JPEGQTable getScaledInstance(float scaleFactor,
                                    boolean forceBaseline)

Returns a new quantization table where the values are multiplied by scaleFactor and then clamped to the range 1..32767 (or to 1..255 if forceBaseline is true).

Values of scaleFactorless than 1 tend to improve the quality level of the table, and values greater than 1.0 degrade the quality level of the table.

Parameters:: scaleFactor - the multiplicative factor for the table.; forceBaseline - if true, the values will be clamped to the range 1..255.
Returns:: a new quantization table that is a linear multiple of the current table.

getTable

public int[] getTable()

Returns a copy of the current quantization table as an array of ints in natural (not zig-zag) order.

Returns:: A copy of the current quantization table.

toString

public String toString()

Overrides:: toString in class Object