* For more information about the operation of the built-in JPEG plug-ins,
* see the JPEG
* metadata format specification and usage notes.
*
* @version 0.5
*/
public class JPEGQTable {
/** Table */
private int[] table;
/** The number of coefficients in a quantization table. */
private static final byte QTABLESIZE = 64;
/**
* 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();
static {
int [] lumVals = {
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
};
K1Luminance.table = lumVals;
}
/**
* 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 =
K1Luminance.getScaledInstance(0.5f, true);
/**
* 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();
static {
int [] chromVals = {
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
};
K2Chrominance.table = chromVals;
}
/**
* 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.
*
* @see #K2Chrominance
*/
public static final JPEGQTable K2Div2Chrominance =
K2Chrominance.getScaledInstance(0.5f, true);
/**
* Constructs an empty quantization table. This is used to create
* the standard tables.
*/
private JPEGQTable() {}
/**
* 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.
*
* @param table the quantization table, as an int
* array.
*
* @exception IllegalArgumentException if table is
* null or table.length is not equal to
* 64.
*/
public JPEGQTable(int[] table) {
if (table == null) {
throw new IllegalArgumentException("table == null!");
}
if (table.length != QTABLESIZE) {
throw new IllegalArgumentException
("Quantization table is the wrong size.");
}
this.table = (int[])table.clone();
}
/**
* Returns a copy of the current quantization table as an array of
* ints in natural (not zig-zag) order.
*
* @return A copy of the current quantization table.
*/
public int[] getTable() {
return (int[])table.clone();
}
/**
* 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.
* @param scaleFactor the multiplicative factor for the table.
* @param forceBaseline if 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[] ret = new int[QTABLESIZE];
for (int i = 0; i < QTABLESIZE; i++) {
float scaledValue = (float)Math.round(table[i]*scaleFactor);
int holder;
// limit to valid range
if (scaledValue <= 1.0F) {
holder = 1;
} else if (scaledValue >= max) {
holder = max;
} else {
holder = (int)scaledValue;
}
ret[i] = holder;
}
return new JPEGQTable(ret);
}
public String toString() {
StringBuffer sb = new StringBuffer();
sb.append("JPEGQTable:\n");
for (int i = 0; i< 8; i++) {
sb.append('\t');
for (int j = 0; j < 8; j++) {
sb.append(table[i]).append(" ");
}
sb.append('\n');
}
return sb.toString();
}
}