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 specification, as well as the default tables conventionally used for visually lossless encoding.
For more information about the operation of the standard JPEG plug-in, see the JPEG metadata format specification and usage notes
Field Summary
Modifier and Type | Field | Description |
---|---|---|
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.1, with all elements divided by 2. |
Constructor Summary
Constructor | Description |
---|---|
JPEGQTable(int[] table) | Constructs a quantization table from the argument, which must contain 64 elements in natural order (not zig-zag order). |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
JPEGQTable | getScaledInstance(float scaleFactor,
boolean forceBaseline) | Returns a new quantization table where the values are multiplied by |
int[] | getTable() | Returns a copy of the current quantization table as an array of |
String | toString() | Returns a |
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Field Detail
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.
- See Also:
K1Div2Luminance
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.
- See Also:
K1Luminance
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.
- See Also:
K2Div2Chrominance
K2Div2Chrominance
public static final JPEGQTable K2Div2Chrominance
The sample chrominance 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 chrominance table used if the default tables and quality settings are used.
- See Also:
K2Chrominance
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 input array.
- Parameters:
-
table
- the quantization table, as anint
array. - Throws:
-
IllegalArgumentException
- iftable
isnull
ortable.length
is not equal to 64.
Method Detail
getTable
public int[] getTable()
Returns a copy of the current quantization table as an array of int
s in natural (not zig-zag) order.
- Returns:
- A copy of the current quantization table.
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 scaleFactor
less 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
- multiplication factor for the table. -
forceBaseline
- iftrue
, the values will be clamped to the range 1..255 - Returns:
- a new quantization table that is a linear multiple of the current table.
toString
public String toString()
Returns a String
representing this quantization table.