java.lang.Object
javax.imageio.plugins.jpeg.JPEGQTable
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 TypeFieldDescriptionstatic final JPEGQTable
The sample luminance quantization table given in the JPEG specification, table K.1, with all elements divided by 2.static final JPEGQTable
The sample luminance quantization table given in the JPEG specification, table K.1.static final JPEGQTable
The sample chrominance quantization table given in the JPEG specification, table K.2.static final JPEGQTable
The sample chrominance quantization table given in the JPEG specification, table K.1, with all elements divided by 2. -
Constructor Summary
ConstructorDescriptionJPEGQTable
(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 TypeMethodDescriptiongetScaledInstance
(float scaleFactor, boolean forceBaseline) Returns a new quantization table where the values are multiplied byscaleFactor
and then clamped to the range 1..32767 (or to 1..255 ifforceBaseline
is true).int[]
getTable()
Returns a copy of the current quantization table as an array ofint
s in natural (not zig-zag) order.toString()
Returns aString
representing this quantization table.
-
Field Details
-
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
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:
-
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
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:
-
-
Constructor Details
-
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 Details
-
getTable
public int[] getTable()Returns a copy of the current quantization table as an array ofint
s in natural (not zig-zag) order.- Returns:
- A copy of the current quantization table.
-
getScaledInstance
Returns a new quantization table where the values are multiplied byscaleFactor
and then clamped to the range 1..32767 (or to 1..255 ifforceBaseline
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
Returns aString
representing this quantization table.
-