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*
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package javax.imageio.plugins.jpeg;
import java.util.Arrays;
/**
* 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.
* <p>
* For more information about the operation of the standard JPEG plug-in,
* see the <A HREF="../../metadata/doc-files/jpeg_metadata.html">JPEG
* metadata format specification and usage notes</A>
*/
public class JPEGQTable {
private static final int[] k1 = {
16, 11, 10, 16, 24, 40, 51, 61,
12, 12, 14, 19, 26, 58, 60, 55,
14, 13, 16, 24, 40, 57, 69, 56,
14, 17, 22, 29, 51, 87, 80, 62,
18, 22, 37, 56, 68, 109, 103, 77,
24, 35, 55, 64, 81, 104, 113, 92,
49, 64, 78, 87, 103, 121, 120, 101,
72, 92, 95, 98, 112, 100, 103, 99,
};
private static final int[] k1div2 = {
8, 6, 5, 8, 12, 20, 26, 31,
6, 6, 7, 10, 13, 29, 30, 28,
7, 7, 8, 12, 20, 29, 35, 28,
7, 9, 11, 15, 26, 44, 40, 31,
9, 11, 19, 28, 34, 55, 52, 39,
12, 18, 28, 32, 41, 52, 57, 46,
25, 32, 39, 44, 52, 61, 60, 51,
36, 46, 48, 49, 56, 50, 52, 50,
};
private static final int[] k2 = {
17, 18, 24, 47, 99, 99, 99, 99,
18, 21, 26, 66, 99, 99, 99, 99,
24, 26, 56, 99, 99, 99, 99, 99,
47, 66, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
};
private static final int[] k2div2 = {
9, 9, 12, 24, 50, 50, 50, 50,
9, 11, 13, 33, 50, 50, 50, 50,
12, 13, 28, 50, 50, 50, 50, 50,
24, 33, 50, 50, 50, 50, 50, 50,
50, 50, 50, 50, 50, 50, 50, 50,
50, 50, 50, 50, 50, 50, 50, 50,
50, 50, 50, 50, 50, 50, 50, 50,
50, 50, 50, 50, 50, 50, 50, 50,
};
/**
* The sample luminance quantization table given in the JPEG
* specification, table K.1. According to the specification,
* these values produce "good" quality output.
* @see #K1Div2Luminance
*/
public static final JPEGQTable
K1Luminance = new JPEGQTable(k1, false);
/**
* 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 #K1Luminance
*/
public static final JPEGQTable
K1Div2Luminance = new JPEGQTable(k1div2, false);
/**
* The sample chrominance quantization table given in the JPEG
* specification, table K.2. According to the specification,
* these values produce "good" quality output.
* @see #K2Div2Chrominance
*/
public static final JPEGQTable K2Chrominance =
new JPEGQTable(k2, false);
/**
* 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 #K2Chrominance
*/
public static final JPEGQTable K2Div2Chrominance =
new JPEGQTable(k2div2, false);
private int[] qTable;
private JPEGQTable(int[] table, boolean copy) {
qTable = (copy) ? Arrays.copyOf(table, table.length) : 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.
* @param table the quantization table, as an {@code int} array.
* @throws IllegalArgumentException if {@code table} is
* {@code null} or {@code table.length} is not equal to 64.
*/
public JPEGQTable(int[] table) {
if (table == null) {
throw new IllegalArgumentException("table must not be null.");
}
if (table.length != 64) {
throw new IllegalArgumentException("table.length != 64");
}
qTable = Arrays.copyOf(table, table.length);
}
/**
* Returns a copy of the current quantization table as an array
* of {@code int}s in natural (not zig-zag) order.
* @return A copy of the current quantization table.
*/
public int[] getTable() {
return Arrays.copyOf(qTable, qTable.length);
}
/**
* Returns a new quantization table where the values are multiplied
* by {@code scaleFactor} and then clamped to the range 1..32767
* (or to 1..255 if {@code forceBaseline} is true).
* <p>
* Values of {@code 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.
* @param scaleFactor multiplication factor for the table.
* @param forceBaseline if {@code true},
* the values will be clamped to the range 1..255
* @return a new quantization table that is a linear multiple
* of the current table.
*/
public JPEGQTable getScaledInstance(float scaleFactor,
boolean forceBaseline) {
int max = (forceBaseline) ? 255 : 32767;
int[] scaledTable = new int[qTable.length];
for (int i=0; i<qTable.length; i++) {
int sv = (int)((qTable[i] * scaleFactor)+0.5f);
if (sv < 1) {
sv = 1;
}
if (sv > max) {
sv = max;
}
scaledTable[i] = sv;
}
return new JPEGQTable(scaledTable);
}
/**
* Returns a {@code String} representing this quantization table.
* @return a {@code String} representing this quantization table.
*/
public String toString() {
String ls = System.getProperty("line.separator", "\n");
StringBuilder sb = new StringBuilder("JPEGQTable:"+ls);
for (int i=0; i < qTable.length; i++) {
if (i % 8 == 0) {
sb.append('\t');
}
sb.append(qTable[i]);
sb.append(((i % 8) == 7) ? ls : ' ');
}
return sb.toString();
}
}