- java.lang.Object
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- javax.imageio.plugins.jpeg.JPEGQTable
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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
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Field Summary
Fields Modifier and Type Field Description static JPEGQTableK1Div2LuminanceThe sample luminance quantization table given in the JPEG specification, table K.1, with all elements divided by 2.static JPEGQTableK1LuminanceThe sample luminance quantization table given in the JPEG specification, table K.1.static JPEGQTableK2ChrominanceThe sample chrominance quantization table given in the JPEG specification, table K.2.static JPEGQTableK2Div2ChrominanceThe sample chrominance quantization table given in the JPEG specification, table K.1, with all elements divided by 2.
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Constructor Summary
Constructors Constructor Description JPEGQTable(int[] table)Constructs a quantization table from the argument, which must contain 64 elements in natural order (not zig-zag order).
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description JPEGQTablegetScaledInstance(float scaleFactor, boolean forceBaseline)Returns a new quantization table where the values are multiplied byscaleFactorand then clamped to the range 1..32767 (or to 1..255 ifforceBaselineis true).int[]getTable()Returns a copy of the current quantization table as an array ofints in natural (not zig-zag) order.StringtoString()Returns aStringrepresenting this quantization table.
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Field Detail
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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
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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
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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
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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
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Constructor Detail
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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 anintarray.- Throws:
IllegalArgumentException- iftableisnullortable.lengthis not equal to 64.
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Method Detail
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getTable
public int[] getTable()
Returns a copy of the current quantization table as an array ofints in natural (not zig-zag) order.- Returns:
- A copy of the current quantization table.
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getScaledInstance
public JPEGQTable getScaledInstance(float scaleFactor, boolean forceBaseline)
Returns a new quantization table where the values are multiplied byscaleFactorand then clamped to the range 1..32767 (or to 1..255 ifforceBaselineis 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- 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.
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