Mega Code Archive
Performs a jpeg compression of an image
<![CDATA[
// Copyright (C) 1998, James R. Weeks and BioElectroMech.
// Visit BioElectroMech at www.obrador.com. Email James@obrador.com.
// This software is based in part on the work of the Independent JPEG Group.
// See license.txt for details about the allowed used of this software.
// See IJGreadme.txt for details about the Independent JPEG Group's license.
import java.awt.AWTException;
import java.awt.Frame;
import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.Toolkit;
import java.awt.image.PixelGrabber;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Vector;
public class Jpeg {
/** ************ Main Method *************** */
/*****************************************************************************
* Jpeg("Imagefile", Quality, "OutFileName") According to JAVA virtual
* machine, the files which can be read are jpeg, tiff and gif files
****************************************************************************/
public static void StandardUsage() {
System.out.println("JpegEncoder for Java(tm) Version 0.9");
System.out.println("");
System.out
.println("Program usage: java Jpeg \"InputImage\".\"ext\" Quality [\"OutputFile\"[.jpg]]");
System.out.println("");
System.out
.println("Where \"InputImage\" is the name of an existing image in the current directory.");
System.out
.println(" (\"InputImage may specify a directory, too.) \"ext\" must be .tif, .gif,");
System.out.println(" or .jpg.");
System.out
.println("Quality is an integer (0 to 100) that specifies how similar the compressed");
System.out
.println(" image is to \"InputImage.\" 100 is almost exactly like \"InputImage\" and 0 is");
System.out.println(" most dissimilar. In most cases, 70 - 80 gives very good results.");
System.out
.println("\"OutputFile\" is an optional argument. If \"OutputFile\" isn't specified, then");
System.out
.println(" the input file name is adopted. This program will NOT write over an existing");
System.out
.println(" file. If a directory is specified for the input image, then \"OutputFile\"");
System.out
.println(" will be written in that directory. The extension \".jpg\" may automatically be");
System.out.println(" added.");
System.out.println("");
System.out
.println("Copyright 1998 BioElectroMech and James R. Weeks. Portions copyright IJG and");
System.out.println(" Florian Raemy, LCAV. See license.txt for details.");
System.out.println("Visit BioElectroMech at www.obrador.com. Email James@obrador.com.");
System.exit(0);
}
public static void main(String args[]) {
Image image = null;
FileOutputStream dataOut = null;
File file, outFile;
JpegEncoder jpg;
String string = "";
int i, Quality = 80;
// Check to see if the input file name has one of the extensions:
// .tif, .gif, .jpg
// If not, print the standard use info.
if (args.length < 2)
StandardUsage();
if (!args[0].endsWith(".jpg") && !args[0].endsWith(".tif") && !args[0].endsWith(".gif"))
StandardUsage();
// First check to see if there is an OutputFile argument. If there isn't
// then name the file "InputFile".jpg
// Second check to see if the .jpg extension is on the OutputFile argument.
// If there isn't one, add it.
// Need to check for the existence of the output file. If it exists already,
// rename the file with a # after the file name, then the .jpg extension.
if (args.length < 3) {
string = args[0].substring(0, args[0].lastIndexOf(".")) + ".jpg";
} else {
string = args[2];
if (string.endsWith(".tif") || string.endsWith(".gif"))
string = string.substring(0, string.lastIndexOf("."));
if (!string.endsWith(".jpg"))
string = string.concat(".jpg");
}
outFile = new File(string);
i = 1;
while (outFile.exists()) {
outFile = new File(string.substring(0, string.lastIndexOf(".")) + (i++) + ".jpg");
if (i > 100)
System.exit(0);
}
file = new File(args[0]);
if (file.exists()) {
try {
dataOut = new FileOutputStream(outFile);
} catch (IOException e) {
}
try {
Quality = Integer.parseInt(args[1]);
} catch (NumberFormatException e) {
StandardUsage();
}
image = Toolkit.getDefaultToolkit().getImage(args[0]);
jpg = new JpegEncoder(image, Quality, dataOut);
jpg.Compress();
try {
dataOut.close();
} catch (IOException e) {
}
} else {
System.out.println("I couldn't find " + args[0] + ". Is it in another directory?");
}
System.exit(0);
}
}
// Version 1.0a
// Copyright (C) 1998, James R. Weeks and BioElectroMech.
// Visit BioElectroMech at www.obrador.com. Email James@obrador.com.
// See license.txt for details about the allowed used of this software.
// This software is based in part on the work of the Independent JPEG Group.
// See IJGreadme.txt for details about the Independent JPEG Group's license.
// This encoder is inspired by the Java Jpeg encoder by Florian Raemy,
// studwww.eurecom.fr/~raemy.
// It borrows a great deal of code and structure from the Independent
// Jpeg Group's Jpeg 6a library, Copyright Thomas G. Lane.
// See license.txt for details.
/*
* JpegEncoder - The JPEG main program which performs a jpeg compression of an
* image.
*/
class JpegEncoder extends Frame {
Thread runner;
BufferedOutputStream outStream;
Image image;
JpegInfo JpegObj;
Huffman Huf;
DCT dct;
int imageHeight, imageWidth;
int Quality;
int code;
public static int[] jpegNaturalOrder = { 0, 1, 8, 16, 9, 2, 3, 10, 17, 24, 32, 25, 18, 11, 4, 5,
12, 19, 26, 33, 40, 48, 41, 34, 27, 20, 13, 6, 7, 14, 21, 28, 35, 42, 49, 56, 57, 50, 43, 36,
29, 22, 15, 23, 30, 37, 44, 51, 58, 59, 52, 45, 38, 31, 39, 46, 53, 60, 61, 54, 47, 55, 62,
63, };
public JpegEncoder(Image image, int quality, OutputStream out) {
MediaTracker tracker = new MediaTracker(this);
tracker.addImage(image, 0);
try {
tracker.waitForID(0);
} catch (InterruptedException e) {
// Got to do something?
}
/*
* Quality of the image. 0 to 100 and from bad image quality, high
* compression to good image quality low compression
*/
Quality = quality;
/*
* Getting picture information It takes the Width, Height and RGB scans of
* the image.
*/
JpegObj = new JpegInfo(image);
imageHeight = JpegObj.imageHeight;
imageWidth = JpegObj.imageWidth;
outStream = new BufferedOutputStream(out);
dct = new DCT(Quality);
Huf = new Huffman(imageWidth, imageHeight);
}
public void setQuality(int quality) {
dct = new DCT(quality);
}
public int getQuality() {
return Quality;
}
public void Compress() {
WriteHeaders(outStream);
WriteCompressedData(outStream);
WriteEOI(outStream);
try {
outStream.flush();
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
}
}
public void WriteCompressedData(BufferedOutputStream outStream) {
int i, j, r, c, a, b;
int comp, xpos, ypos, xblockoffset, yblockoffset;
float inputArray[][];
float dctArray1[][] = new float[8][8];
double dctArray2[][] = new double[8][8];
int dctArray3[] = new int[8 * 8];
/*
* This method controls the compression of the image. Starting at the upper
* left of the image, it compresses 8x8 blocks of data until the entire
* image has been compressed.
*/
int lastDCvalue[] = new int[JpegObj.NumberOfComponents];
// int zeroArray[] = new int[64]; // initialized to hold all zeros
// int Width = 0, Height = 0;
// int nothing = 0, not;
int MinBlockWidth, MinBlockHeight;
// This initial setting of MinBlockWidth and MinBlockHeight is done to
// ensure they start with values larger than will actually be the case.
MinBlockWidth = ((imageWidth % 8 != 0) ? (int) (Math.floor(imageWidth / 8.0) + 1) * 8
: imageWidth);
MinBlockHeight = ((imageHeight % 8 != 0) ? (int) (Math.floor(imageHeight / 8.0) + 1) * 8
: imageHeight);
for (comp = 0; comp < JpegObj.NumberOfComponents; comp++) {
MinBlockWidth = Math.min(MinBlockWidth, JpegObj.BlockWidth[comp]);
MinBlockHeight = Math.min(MinBlockHeight, JpegObj.BlockHeight[comp]);
}
xpos = 0;
for (r = 0; r < MinBlockHeight; r++) {
for (c = 0; c < MinBlockWidth; c++) {
xpos = c * 8;
ypos = r * 8;
for (comp = 0; comp < JpegObj.NumberOfComponents; comp++) {
// Width = JpegObj.BlockWidth[comp];
// Height = JpegObj.BlockHeight[comp];
inputArray = (float[][]) JpegObj.Components[comp];
for (i = 0; i < JpegObj.VsampFactor[comp]; i++) {
for (j = 0; j < JpegObj.HsampFactor[comp]; j++) {
xblockoffset = j * 8;
yblockoffset = i * 8;
for (a = 0; a < 8; a++) {
for (b = 0; b < 8; b++) {
// I believe this is where the dirty line at the bottom of
// the image is coming from.
// I need to do a check here to make sure I'm not reading past
// image data.
// This seems to not be a big issue right now. (04/04/98)
dctArray1[a][b] = inputArray[ypos + yblockoffset + a][xpos + xblockoffset + b];
}
}
// The following code commented out because on some images this
// technique
// results in poor right and bottom borders.
// if ((!JpegObj.lastColumnIsDummy[comp] || c < Width - 1) &&
// (!JpegObj.lastRowIsDummy[comp] || r < Height - 1)) {
dctArray2 = dct.forwardDCT(dctArray1);
dctArray3 = dct.quantizeBlock(dctArray2, JpegObj.QtableNumber[comp]);
// }
// else {
// zeroArray[0] = dctArray3[0];
// zeroArray[0] = lastDCvalue[comp];
// dctArray3 = zeroArray;
// }
Huf.HuffmanBlockEncoder(outStream, dctArray3, lastDCvalue[comp],
JpegObj.DCtableNumber[comp], JpegObj.ACtableNumber[comp]);
lastDCvalue[comp] = dctArray3[0];
}
}
}
}
}
Huf.flushBuffer(outStream);
}
public void WriteEOI(BufferedOutputStream out) {
byte[] EOI = { (byte) 0xFF, (byte) 0xD9 };
WriteMarker(EOI, out);
}
public void WriteHeaders(BufferedOutputStream out) {
int i, j, index, offset, length;
int tempArray[];
// the SOI marker
byte[] SOI = { (byte) 0xFF, (byte) 0xD8 };
WriteMarker(SOI, out);
// The order of the following headers is quiet inconsequential.
// the JFIF header
byte JFIF[] = new byte[18];
JFIF[0] = (byte) 0xff;
JFIF[1] = (byte) 0xe0;
JFIF[2] = (byte) 0x00;
JFIF[3] = (byte) 0x10;
JFIF[4] = (byte) 0x4a;
JFIF[5] = (byte) 0x46;
JFIF[6] = (byte) 0x49;
JFIF[7] = (byte) 0x46;
JFIF[8] = (byte) 0x00;
JFIF[9] = (byte) 0x01;
JFIF[10] = (byte) 0x00;
JFIF[11] = (byte) 0x00;
JFIF[12] = (byte) 0x00;
JFIF[13] = (byte) 0x01;
JFIF[14] = (byte) 0x00;
JFIF[15] = (byte) 0x01;
JFIF[16] = (byte) 0x00;
JFIF[17] = (byte) 0x00;
WriteArray(JFIF, out);
// Comment Header
String comment = "";
comment = JpegObj.getComment();
length = comment.length();
byte COM[] = new byte[length + 4];
COM[0] = (byte) 0xFF;
COM[1] = (byte) 0xFE;
COM[2] = (byte) ((length >> 8) & 0xFF);
COM[3] = (byte) (length & 0xFF);
java.lang.System.arraycopy(JpegObj.Comment.getBytes(), 0, COM, 4, JpegObj.Comment.length());
WriteArray(COM, out);
// The DQT header
// 0 is the luminance index and 1 is the chrominance index
byte DQT[] = new byte[134];
DQT[0] = (byte) 0xFF;
DQT[1] = (byte) 0xDB;
DQT[2] = (byte) 0x00;
DQT[3] = (byte) 0x84;
offset = 4;
for (i = 0; i < 2; i++) {
DQT[offset++] = (byte) ((0 << 4) + i);
tempArray = (int[]) dct.quantum[i];
for (j = 0; j < 64; j++) {
DQT[offset++] = (byte) tempArray[jpegNaturalOrder[j]];
}
}
WriteArray(DQT, out);
// Start of Frame Header
byte SOF[] = new byte[19];
SOF[0] = (byte) 0xFF;
SOF[1] = (byte) 0xC0;
SOF[2] = (byte) 0x00;
SOF[3] = (byte) 17;
SOF[4] = (byte) JpegObj.Precision;
SOF[5] = (byte) ((JpegObj.imageHeight >> 8) & 0xFF);
SOF[6] = (byte) ((JpegObj.imageHeight) & 0xFF);
SOF[7] = (byte) ((JpegObj.imageWidth >> 8) & 0xFF);
SOF[8] = (byte) ((JpegObj.imageWidth) & 0xFF);
SOF[9] = (byte) JpegObj.NumberOfComponents;
index = 10;
for (i = 0; i < SOF[9]; i++) {
SOF[index++] = (byte) JpegObj.CompID[i];
SOF[index++] = (byte) ((JpegObj.HsampFactor[i] << 4) + JpegObj.VsampFactor[i]);
SOF[index++] = (byte) JpegObj.QtableNumber[i];
}
WriteArray(SOF, out);
// The DHT Header
byte DHT1[], DHT2[], DHT3[], DHT4[];
int bytes, temp, oldindex, intermediateindex;
length = 2;
index = 4;
oldindex = 4;
DHT1 = new byte[17];
DHT4 = new byte[4];
DHT4[0] = (byte) 0xFF;
DHT4[1] = (byte) 0xC4;
for (i = 0; i < 4; i++) {
bytes = 0;
DHT1[index++ - oldindex] = (byte) ((int[]) Huf.bits.elementAt(i))[0];
for (j = 1; j < 17; j++) {
temp = ((int[]) Huf.bits.elementAt(i))[j];
DHT1[index++ - oldindex] = (byte) temp;
bytes += temp;
}
intermediateindex = index;
DHT2 = new byte[bytes];
for (j = 0; j < bytes; j++) {
DHT2[index++ - intermediateindex] = (byte) ((int[]) Huf.val.elementAt(i))[j];
}
DHT3 = new byte[index];
java.lang.System.arraycopy(DHT4, 0, DHT3, 0, oldindex);
java.lang.System.arraycopy(DHT1, 0, DHT3, oldindex, 17);
java.lang.System.arraycopy(DHT2, 0, DHT3, oldindex + 17, bytes);
DHT4 = DHT3;
oldindex = index;
}
DHT4[2] = (byte) (((index - 2) >> 8) & 0xFF);
DHT4[3] = (byte) ((index - 2) & 0xFF);
WriteArray(DHT4, out);
// Start of Scan Header
byte SOS[] = new byte[14];
SOS[0] = (byte) 0xFF;
SOS[1] = (byte) 0xDA;
SOS[2] = (byte) 0x00;
SOS[3] = (byte) 12;
SOS[4] = (byte) JpegObj.NumberOfComponents;
index = 5;
for (i = 0; i < SOS[4]; i++) {
SOS[index++] = (byte) JpegObj.CompID[i];
SOS[index++] = (byte) ((JpegObj.DCtableNumber[i] << 4) + JpegObj.ACtableNumber[i]);
}
SOS[index++] = (byte) JpegObj.Ss;
SOS[index++] = (byte) JpegObj.Se;
SOS[index++] = (byte) ((JpegObj.Ah << 4) + JpegObj.Al);
WriteArray(SOS, out);
}
void WriteMarker(byte[] data, BufferedOutputStream out) {
try {
out.write(data, 0, 2);
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
}
}
void WriteArray(byte[] data, BufferedOutputStream out) {
int length;
try {
length = ((data[2] & 0xFF) << 8) + (data[3] & 0xFF) + 2;
out.write(data, 0, length);
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
}
}
}
// This class incorporates quality scaling as implemented in the JPEG-6a
// library.
/*
* DCT - A Java implementation of the Discreet Cosine Transform
*/
class DCT {
/**
* DCT Block Size - default 8
*/
public int N = 8;
/**
* Image Quality (0-100) - default 80 (good image / good compression)
*/
public int QUALITY = 80;
public Object quantum[] = new Object[2];
public Object Divisors[] = new Object[2];
/**
* Quantitization Matrix for luminace.
*/
public int quantum_luminance[] = new int[N * N];
public double DivisorsLuminance[] = new double[N * N];
/**
* Quantitization Matrix for chrominance.
*/
public int quantum_chrominance[] = new int[N * N];
public double DivisorsChrominance[] = new double[N * N];
/**
* Constructs a new DCT object. Initializes the cosine transform matrix these
* are used when computing the DCT and it's inverse. This also initializes the
* run length counters and the ZigZag sequence. Note that the image quality
* can be worse than 25 however the image will be extemely pixelated, usually
* to a block size of N.
*
* @param QUALITY
* The quality of the image (0 worst - 100 best)
*
*/
public DCT(int QUALITY) {
initMatrix(QUALITY);
}
/*
* This method sets up the quantization matrix for luminance and chrominance
* using the Quality parameter.
*/
private void initMatrix(int quality) {
double[] AANscaleFactor = { 1.0, 1.387039845, 1.306562965, 1.175875602, 1.0, 0.785694958,
0.541196100, 0.275899379 };
int i;
int j;
int index;
int Quality;
int temp;
// converting quality setting to that specified in the jpeg_quality_scaling
// method in the IJG Jpeg-6a C libraries
Quality = quality;
if (Quality <= 0)
Quality = 1;
if (Quality > 100)
Quality = 100;
if (Quality < 50)
Quality = 5000 / Quality;
else
Quality = 200 - Quality * 2;
// Creating the luminance matrix
quantum_luminance[0] = 16;
quantum_luminance[1] = 11;
quantum_luminance[2] = 10;
quantum_luminance[3] = 16;
quantum_luminance[4] = 24;
quantum_luminance[5] = 40;
quantum_luminance[6] = 51;
quantum_luminance[7] = 61;
quantum_luminance[8] = 12;
quantum_luminance[9] = 12;
quantum_luminance[10] = 14;
quantum_luminance[11] = 19;
quantum_luminance[12] = 26;
quantum_luminance[13] = 58;
quantum_luminance[14] = 60;
quantum_luminance[15] = 55;
quantum_luminance[16] = 14;
quantum_luminance[17] = 13;
quantum_luminance[18] = 16;
quantum_luminance[19] = 24;
quantum_luminance[20] = 40;
quantum_luminance[21] = 57;
quantum_luminance[22] = 69;
quantum_luminance[23] = 56;
quantum_luminance[24] = 14;
quantum_luminance[25] = 17;
quantum_luminance[26] = 22;
quantum_luminance[27] = 29;
quantum_luminance[28] = 51;
quantum_luminance[29] = 87;
quantum_luminance[30] = 80;
quantum_luminance[31] = 62;
quantum_luminance[32] = 18;
quantum_luminance[33] = 22;
quantum_luminance[34] = 37;
quantum_luminance[35] = 56;
quantum_luminance[36] = 68;
quantum_luminance[37] = 109;
quantum_luminance[38] = 103;
quantum_luminance[39] = 77;
quantum_luminance[40] = 24;
quantum_luminance[41] = 35;
quantum_luminance[42] = 55;
quantum_luminance[43] = 64;
quantum_luminance[44] = 81;
quantum_luminance[45] = 104;
quantum_luminance[46] = 113;
quantum_luminance[47] = 92;
quantum_luminance[48] = 49;
quantum_luminance[49] = 64;
quantum_luminance[50] = 78;
quantum_luminance[51] = 87;
quantum_luminance[52] = 103;
quantum_luminance[53] = 121;
quantum_luminance[54] = 120;
quantum_luminance[55] = 101;
quantum_luminance[56] = 72;
quantum_luminance[57] = 92;
quantum_luminance[58] = 95;
quantum_luminance[59] = 98;
quantum_luminance[60] = 112;
quantum_luminance[61] = 100;
quantum_luminance[62] = 103;
quantum_luminance[63] = 99;
for (j = 0; j < 64; j++) {
temp = (quantum_luminance[j] * Quality + 50) / 100;
if (temp <= 0)
temp = 1;
if (temp > 255)
temp = 255;
quantum_luminance[j] = temp;
}
index = 0;
for (i = 0; i < 8; i++) {
for (j = 0; j < 8; j++) {
// The divisors for the LL&M method (the slow integer method used in
// jpeg 6a library). This method is currently (04/04/98) incompletely
// implemented.
// DivisorsLuminance[index] = ((double) quantum_luminance[index]) << 3;
// The divisors for the AAN method (the float method used in jpeg 6a
// library.
DivisorsLuminance[index] = (1.0 / (quantum_luminance[index] * AANscaleFactor[i]
* AANscaleFactor[j] * 8.0));
index++;
}
}
// Creating the chrominance matrix
quantum_chrominance[0] = 17;
quantum_chrominance[1] = 18;
quantum_chrominance[2] = 24;
quantum_chrominance[3] = 47;
quantum_chrominance[4] = 99;
quantum_chrominance[5] = 99;
quantum_chrominance[6] = 99;
quantum_chrominance[7] = 99;
quantum_chrominance[8] = 18;
quantum_chrominance[9] = 21;
quantum_chrominance[10] = 26;
quantum_chrominance[11] = 66;
quantum_chrominance[12] = 99;
quantum_chrominance[13] = 99;
quantum_chrominance[14] = 99;
quantum_chrominance[15] = 99;
quantum_chrominance[16] = 24;
quantum_chrominance[17] = 26;
quantum_chrominance[18] = 56;
quantum_chrominance[19] = 99;
quantum_chrominance[20] = 99;
quantum_chrominance[21] = 99;
quantum_chrominance[22] = 99;
quantum_chrominance[23] = 99;
quantum_chrominance[24] = 47;
quantum_chrominance[25] = 66;
quantum_chrominance[26] = 99;
quantum_chrominance[27] = 99;
quantum_chrominance[28] = 99;
quantum_chrominance[29] = 99;
quantum_chrominance[30] = 99;
quantum_chrominance[31] = 99;
quantum_chrominance[32] = 99;
quantum_chrominance[33] = 99;
quantum_chrominance[34] = 99;
quantum_chrominance[35] = 99;
quantum_chrominance[36] = 99;
quantum_chrominance[37] = 99;
quantum_chrominance[38] = 99;
quantum_chrominance[39] = 99;
quantum_chrominance[40] = 99;
quantum_chrominance[41] = 99;
quantum_chrominance[42] = 99;
quantum_chrominance[43] = 99;
quantum_chrominance[44] = 99;
quantum_chrominance[45] = 99;
quantum_chrominance[46] = 99;
quantum_chrominance[47] = 99;
quantum_chrominance[48] = 99;
quantum_chrominance[49] = 99;
quantum_chrominance[50] = 99;
quantum_chrominance[51] = 99;
quantum_chrominance[52] = 99;
quantum_chrominance[53] = 99;
quantum_chrominance[54] = 99;
quantum_chrominance[55] = 99;
quantum_chrominance[56] = 99;
quantum_chrominance[57] = 99;
quantum_chrominance[58] = 99;
quantum_chrominance[59] = 99;
quantum_chrominance[60] = 99;
quantum_chrominance[61] = 99;
quantum_chrominance[62] = 99;
quantum_chrominance[63] = 99;
for (j = 0; j < 64; j++) {
temp = (quantum_chrominance[j] * Quality + 50) / 100;
if (temp <= 0)
temp = 1;
if (temp >= 255)
temp = 255;
quantum_chrominance[j] = temp;
}
index = 0;
for (i = 0; i < 8; i++) {
for (j = 0; j < 8; j++) {
// The divisors for the LL&M method (the slow integer method used in
// jpeg 6a library). This method is currently (04/04/98) incompletely
// implemented.
// DivisorsChrominance[index] = ((double) quantum_chrominance[index]) <<
// 3;
// The divisors for the AAN method (the float method used in jpeg 6a
// library.
DivisorsChrominance[index] = 1.0 / (quantum_chrominance[index] * AANscaleFactor[i]
* AANscaleFactor[j] * 8.0);
index++;
}
}
// quantum and Divisors are objects used to hold the appropriate matices
quantum[0] = quantum_luminance;
Divisors[0] = DivisorsLuminance;
quantum[1] = quantum_chrominance;
Divisors[1] = DivisorsChrominance;
}
/*
* This method preforms forward DCT on a block of image data using the literal
* method specified for a 2-D Discrete Cosine Transform. It is included as a
* curiosity and can give you an idea of the difference in the compression
* result (the resulting image quality) by comparing its output to the output
* of the AAN method below. It is ridiculously inefficient.
*/
// For now the final output is unusable. The associated quantization step
// needs some tweaking. If you get this part working, please let me know.
public double[][] forwardDCTExtreme(float input[][]) {
double output[][] = new double[N][N];
int v, u, x, y;
for (v = 0; v < 8; v++) {
for (u = 0; u < 8; u++) {
for (x = 0; x < 8; x++) {
for (y = 0; y < 8; y++) {
output[v][u] += input[x][y]
* Math.cos(((double) (2 * x + 1) * (double) u * Math.PI) / 16)
* Math.cos(((double) (2 * y + 1) * (double) v * Math.PI) / 16);
}
}
output[v][u] *= (0.25) * ((u == 0) ? (1.0 / Math.sqrt(2)) : (double) 1.0)
* ((v == 0) ? (1.0 / Math.sqrt(2)) : (double) 1.0);
}
}
return output;
}
/*
* This method preforms a DCT on a block of image data using the AAN method as
* implemented in the IJG Jpeg-6a library.
*/
public double[][] forwardDCT(float input[][]) {
double output[][] = new double[N][N];
double tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
double tmp10, tmp11, tmp12, tmp13;
double z1, z2, z3, z4, z5, z11, z13;
int i;
int j;
// Subtracts 128 from the input values
for (i = 0; i < 8; i++) {
for (j = 0; j < 8; j++) {
output[i][j] = (input[i][j] - 128.0);
// input[i][j] -= 128;
}
}
for (i = 0; i < 8; i++) {
tmp0 = output[i][0] + output[i][7];
tmp7 = output[i][0] - output[i][7];
tmp1 = output[i][1] + output[i][6];
tmp6 = output[i][1] - output[i][6];
tmp2 = output[i][2] + output[i][5];
tmp5 = output[i][2] - output[i][5];
tmp3 = output[i][3] + output[i][4];
tmp4 = output[i][3] - output[i][4];
tmp10 = tmp0 + tmp3;
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;
output[i][0] = tmp10 + tmp11;
output[i][4] = tmp10 - tmp11;
z1 = (tmp12 + tmp13) * 0.707106781;
output[i][2] = tmp13 + z1;
output[i][6] = tmp13 - z1;
tmp10 = tmp4 + tmp5;
tmp11 = tmp5 + tmp6;
tmp12 = tmp6 + tmp7;
z5 = (tmp10 - tmp12) * 0.382683433;
z2 = 0.541196100 * tmp10 + z5;
z4 = 1.306562965 * tmp12 + z5;
z3 = tmp11 * 0.707106781;
z11 = tmp7 + z3;
z13 = tmp7 - z3;
output[i][5] = z13 + z2;
output[i][3] = z13 - z2;
output[i][1] = z11 + z4;
output[i][7] = z11 - z4;
}
for (i = 0; i < 8; i++) {
tmp0 = output[0][i] + output[7][i];
tmp7 = output[0][i] - output[7][i];
tmp1 = output[1][i] + output[6][i];
tmp6 = output[1][i] - output[6][i];
tmp2 = output[2][i] + output[5][i];
tmp5 = output[2][i] - output[5][i];
tmp3 = output[3][i] + output[4][i];
tmp4 = output[3][i] - output[4][i];
tmp10 = tmp0 + tmp3;
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;
output[0][i] = tmp10 + tmp11;
output[4][i] = tmp10 - tmp11;
z1 = (tmp12 + tmp13) * 0.707106781;
output[2][i] = tmp13 + z1;
output[6][i] = tmp13 - z1;
tmp10 = tmp4 + tmp5;
tmp11 = tmp5 + tmp6;
tmp12 = tmp6 + tmp7;
z5 = (tmp10 - tmp12) * 0.382683433;
z2 = 0.541196100 * tmp10 + z5;
z4 = 1.306562965 * tmp12 + z5;
z3 = tmp11 * 0.707106781;
z11 = tmp7 + z3;
z13 = tmp7 - z3;
output[5][i] = z13 + z2;
output[3][i] = z13 - z2;
output[1][i] = z11 + z4;
output[7][i] = z11 - z4;
}
return output;
}
/*
* This method quantitizes data and rounds it to the nearest integer.
*/
public int[] quantizeBlock(double inputData[][], int code) {
int outputData[] = new int[N * N];
int i, j;
int index;
index = 0;
for (i = 0; i < 8; i++) {
for (j = 0; j < 8; j++) {
// The second line results in significantly better compression.
outputData[index] = (int) (Math.round(inputData[i][j]
* (((double[]) (Divisors[code]))[index])));
// outputData[index] = (int)(((inputData[i][j] * (((double[])
// (Divisors[code]))[index])) + 16384.5) -16384);
index++;
}
}
return outputData;
}
/*
* This is the method for quantizing a block DCT'ed with forwardDCTExtreme
* This method quantitizes data and rounds it to the nearest integer.
*/
public int[] quantizeBlockExtreme(double inputData[][], int code) {
int outputData[] = new int[N * N];
int i, j;
int index;
index = 0;
for (i = 0; i < 8; i++) {
for (j = 0; j < 8; j++) {
outputData[index] = (int) (Math.round(inputData[i][j] / (((int[]) (quantum[code]))[index])));
index++;
}
}
return outputData;
}
}
// This class was modified by James R. Weeks on 3/27/98.
// It now incorporates Huffman table derivation as in the C jpeg library
// from the IJG, Jpeg-6a.
class Huffman {
int bufferPutBits, bufferPutBuffer;
public int ImageHeight;
public int ImageWidth;
public int DC_matrix0[][];
public int AC_matrix0[][];
public int DC_matrix1[][];
public int AC_matrix1[][];
public Object DC_matrix[];
public Object AC_matrix[];
public int code;
public int NumOfDCTables;
public int NumOfACTables;
public int[] bitsDCluminance = { 0x00, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0 };
public int[] valDCluminance = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
public int[] bitsDCchrominance = { 0x01, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
public int[] valDCchrominance = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
public int[] bitsACluminance = { 0x10, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d };
public int[] valACluminance = { 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12, 0x21, 0x31, 0x41,
0x06, 0x13, 0x51, 0x61, 0x07, 0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08, 0x23, 0x42,
0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0, 0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16, 0x17,
0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77,
0x78, 0x79, 0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95,
0x96, 0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2,
0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 0xc8,
0xc9, 0xca, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2, 0xe3, 0xe4,
0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9,
0xfa };
public int[] bitsACchrominance = { 0x11, 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77 };
public int[] valACchrominance = { 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21, 0x31, 0x06,
0x12, 0x41, 0x51, 0x07, 0x61, 0x71, 0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91, 0xa1,
0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0, 0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34,
0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37,
0x38, 0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x53, 0x54, 0x55, 0x56,
0x57, 0x58, 0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x73, 0x74, 0x75,
0x76, 0x77, 0x78, 0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x92,
0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 0xa8,
0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5,
0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe2,
0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
0xf9, 0xfa };
public Vector bits;
public Vector val;
/*
* jpegNaturalOrder[i] is the natural-order position of the i'th element of
* zigzag order.
*/
public static int[] jpegNaturalOrder = { 0, 1, 8, 16, 9, 2, 3, 10, 17, 24, 32, 25, 18, 11, 4, 5,
12, 19, 26, 33, 40, 48, 41, 34, 27, 20, 13, 6, 7, 14, 21, 28, 35, 42, 49, 56, 57, 50, 43, 36,
29, 22, 15, 23, 30, 37, 44, 51, 58, 59, 52, 45, 38, 31, 39, 46, 53, 60, 61, 54, 47, 55, 62,
63, };
/*
* The Huffman class constructor
*/
public Huffman(int Width, int Height) {
bits = new Vector();
bits.addElement(bitsDCluminance);
bits.addElement(bitsACluminance);
bits.addElement(bitsDCchrominance);
bits.addElement(bitsACchrominance);
val = new Vector();
val.addElement(valDCluminance);
val.addElement(valACluminance);
val.addElement(valDCchrominance);
val.addElement(valACchrominance);
initHuf();
ImageWidth = Width;
ImageHeight = Height;
}
/**
* HuffmanBlockEncoder run length encodes and Huffman encodes the quantized
* data.
*
* @param outStream
* @param zigzag
* @param prec
* @param DCcode
* @param ACcode
*/
public void HuffmanBlockEncoder(BufferedOutputStream outStream, int zigzag[], int prec,
int DCcode, int ACcode) {
int temp, temp2, nbits, k, r, i;
NumOfDCTables = 2;
NumOfACTables = 2;
// The DC portion
temp = temp2 = zigzag[0] - prec;
if (temp < 0) {
temp = -temp;
temp2--;
}
nbits = 0;
while (temp != 0) {
nbits++;
temp >>= 1;
}
// if (nbits > 11) nbits = 11;
bufferIt(outStream, ((int[][]) DC_matrix[DCcode])[nbits][0],
((int[][]) DC_matrix[DCcode])[nbits][1]);
// The arguments in bufferIt are code and size.
if (nbits != 0) {
bufferIt(outStream, temp2, nbits);
}
// The AC portion
r = 0;
for (k = 1; k < 64; k++) {
if ((temp = zigzag[jpegNaturalOrder[k]]) == 0) {
r++;
} else {
while (r > 15) {
bufferIt(outStream, ((int[][]) AC_matrix[ACcode])[0xF0][0],
((int[][]) AC_matrix[ACcode])[0xF0][1]);
r -= 16;
}
temp2 = temp;
if (temp < 0) {
temp = -temp;
temp2--;
}
nbits = 1;
while ((temp >>= 1) != 0) {
nbits++;
}
i = (r << 4) + nbits;
bufferIt(outStream, ((int[][]) AC_matrix[ACcode])[i][0],
((int[][]) AC_matrix[ACcode])[i][1]);
bufferIt(outStream, temp2, nbits);
r = 0;
}
}
if (r > 0) {
bufferIt(outStream, ((int[][]) AC_matrix[ACcode])[0][0], ((int[][]) AC_matrix[ACcode])[0][1]);
}
}
// Uses an integer long (32 bits) buffer to store the Huffman encoded bits
// and sends them to outStream by the byte.
void bufferIt(BufferedOutputStream outStream, int code, int size) {
int PutBuffer = code;
int PutBits = bufferPutBits;
PutBuffer &= (1 << size) - 1;
PutBits += size;
PutBuffer <<= 24 - PutBits;
PutBuffer |= bufferPutBuffer;
while (PutBits >= 8) {
int c = ((PutBuffer >> 16) & 0xFF);
try {
outStream.write(c);
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
}
if (c == 0xFF) {
try {
outStream.write(0);
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
}
}
PutBuffer <<= 8;
PutBits -= 8;
}
bufferPutBuffer = PutBuffer;
bufferPutBits = PutBits;
}
void flushBuffer(BufferedOutputStream outStream) {
int PutBuffer = bufferPutBuffer;
int PutBits = bufferPutBits;
while (PutBits >= 8) {
int c = ((PutBuffer >> 16) & 0xFF);
try {
outStream.write(c);
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
}
if (c == 0xFF) {
try {
outStream.write(0);
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
}
}
PutBuffer <<= 8;
PutBits -= 8;
}
if (PutBits > 0) {
int c = ((PutBuffer >> 16) & 0xFF);
try {
outStream.write(c);
} catch (IOException e) {
System.out.println("IO Error: " + e.getMessage());
}
}
}
/*
* Initialisation of the Huffman codes for Luminance and Chrominance. This
* code results in the same tables created in the IJG Jpeg-6a library.
*/
public void initHuf() {
DC_matrix0 = new int[12][2];
DC_matrix1 = new int[12][2];
AC_matrix0 = new int[255][2];
AC_matrix1 = new int[255][2];
DC_matrix = new Object[2];
AC_matrix = new Object[2];
int p, l, i, lastp, si, code;
int[] huffsize = new int[257];
int[] huffcode = new int[257];
/*
* init of the DC values for the chrominance [][0] is the code [][1] is the
* number of bit
*/
p = 0;
for (l = 1; l <= 16; l++) {
for (i = 1; i <= bitsDCchrominance[l]; i++) {
huffsize[p++] = l;
}
}
huffsize[p] = 0;
lastp = p;
code = 0;
si = huffsize[0];
p = 0;
while (huffsize[p] != 0) {
while (huffsize[p] == si) {
huffcode[p++] = code;
code++;
}
code <<= 1;
si++;
}
for (p = 0; p < lastp; p++) {
DC_matrix1[valDCchrominance[p]][0] = huffcode[p];
DC_matrix1[valDCchrominance[p]][1] = huffsize[p];
}
/*
* Init of the AC hufmann code for the chrominance matrix [][][0] is the
* code & matrix[][][1] is the number of bit needed
*/
p = 0;
for (l = 1; l <= 16; l++) {
for (i = 1; i <= bitsACchrominance[l]; i++) {
huffsize[p++] = l;
}
}
huffsize[p] = 0;
lastp = p;
code = 0;
si = huffsize[0];
p = 0;
while (huffsize[p] != 0) {
while (huffsize[p] == si) {
huffcode[p++] = code;
code++;
}
code <<= 1;
si++;
}
for (p = 0; p < lastp; p++) {
AC_matrix1[valACchrominance[p]][0] = huffcode[p];
AC_matrix1[valACchrominance[p]][1] = huffsize[p];
}
/*
* init of the DC values for the luminance [][0] is the code [][1] is the
* number of bit
*/
p = 0;
for (l = 1; l <= 16; l++) {
for (i = 1; i <= bitsDCluminance[l]; i++) {
huffsize[p++] = l;
}
}
huffsize[p] = 0;
lastp = p;
code = 0;
si = huffsize[0];
p = 0;
while (huffsize[p] != 0) {
while (huffsize[p] == si) {
huffcode[p++] = code;
code++;
}
code <<= 1;
si++;
}
for (p = 0; p < lastp; p++) {
DC_matrix0[valDCluminance[p]][0] = huffcode[p];
DC_matrix0[valDCluminance[p]][1] = huffsize[p];
}
/*
* Init of the AC hufmann code for luminance matrix [][][0] is the code &
* matrix[][][1] is the number of bit
*/
p = 0;
for (l = 1; l <= 16; l++) {
for (i = 1; i <= bitsACluminance[l]; i++) {
huffsize[p++] = l;
}
}
huffsize[p] = 0;
lastp = p;
code = 0;
si = huffsize[0];
p = 0;
while (huffsize[p] != 0) {
while (huffsize[p] == si) {
huffcode[p++] = code;
code++;
}
code <<= 1;
si++;
}
for (int q = 0; q < lastp; q++) {
AC_matrix0[valACluminance[q]][0] = huffcode[q];
AC_matrix0[valACluminance[q]][1] = huffsize[q];
}
DC_matrix[0] = DC_matrix0;
DC_matrix[1] = DC_matrix1;
AC_matrix[0] = AC_matrix0;
AC_matrix[1] = AC_matrix1;
}
}
/*
* JpegInfo - Given an image, sets default information about it and divides it
* into its constituant components, downsizing those that need to be.
*/
class JpegInfo {
String Comment;
public Image imageobj;
public int imageHeight;
public int imageWidth;
public int BlockWidth[];
public int BlockHeight[];
// the following are set as the default
public int Precision = 8;
public int NumberOfComponents = 3;
public Object Components[];
public int[] CompID = { 1, 2, 3 };
public int[] HsampFactor = { 1, 1, 1 };
public int[] VsampFactor = { 1, 1, 1 };
public int[] QtableNumber = { 0, 1, 1 };
public int[] DCtableNumber = { 0, 1, 1 };
public int[] ACtableNumber = { 0, 1, 1 };
public boolean[] lastColumnIsDummy = { false, false, false };
public boolean[] lastRowIsDummy = { false, false, false };
public int Ss = 0;
public int Se = 63;
public int Ah = 0;
public int Al = 0;
public int compWidth[], compHeight[];
public int MaxHsampFactor;
public int MaxVsampFactor;
public JpegInfo(Image image) {
Components = new Object[NumberOfComponents];
compWidth = new int[NumberOfComponents];
compHeight = new int[NumberOfComponents];
BlockWidth = new int[NumberOfComponents];
BlockHeight = new int[NumberOfComponents];
imageobj = image;
imageWidth = image.getWidth(null);
imageHeight = image.getHeight(null);
Comment = "JPEG Encoder Copyright 1998, James R. Weeks and BioElectroMech. ";
getYCCArray();
}
public void setComment(String comment) {
Comment.concat(comment);
}
public String getComment() {
return Comment;
}
/*
* This method creates and fills three arrays, Y, Cb, and Cr using the input
* image.
*/
private void getYCCArray() {
int values[] = new int[imageWidth * imageHeight];
int r, g, b, y, x;
// In order to minimize the chance that grabPixels will throw an exception
// it may be necessary to grab some pixels every few scanlines and process
// those before going for more. The time expense may be prohibitive.
// However, for a situation where memory overhead is a concern, this may be
// the only choice.
PixelGrabber grabber = new PixelGrabber(imageobj.getSource(), 0, 0, imageWidth, imageHeight,
values, 0, imageWidth);
MaxHsampFactor = 1;
MaxVsampFactor = 1;
for (y = 0; y < NumberOfComponents; y++) {
MaxHsampFactor = Math.max(MaxHsampFactor, HsampFactor[y]);
MaxVsampFactor = Math.max(MaxVsampFactor, VsampFactor[y]);
}
for (y = 0; y < NumberOfComponents; y++) {
compWidth[y] = (((imageWidth % 8 != 0) ? ((int) Math.ceil(imageWidth / 8.0)) * 8 : imageWidth) / MaxHsampFactor)
* HsampFactor[y];
if (compWidth[y] != ((imageWidth / MaxHsampFactor) * HsampFactor[y])) {
lastColumnIsDummy[y] = true;
}
// results in a multiple of 8 for compWidth
// this will make the rest of the program fail for the unlikely
// event that someone tries to compress an 16 x 16 pixel image
// which would of course be worse than pointless
BlockWidth[y] = (int) Math.ceil(compWidth[y] / 8.0);
compHeight[y] = (((imageHeight % 8 != 0) ? ((int) Math.ceil(imageHeight / 8.0)) * 8
: imageHeight) / MaxVsampFactor)
* VsampFactor[y];
if (compHeight[y] != ((imageHeight / MaxVsampFactor) * VsampFactor[y])) {
lastRowIsDummy[y] = true;
}
BlockHeight[y] = (int) Math.ceil(compHeight[y] / 8.0);
}
try {
if (grabber.grabPixels() != true) {
try {
throw new AWTException("Grabber returned false: " + grabber.status());
} catch (Exception e) {
}
}
} catch (InterruptedException e) {
}
float Y[][] = new float[compHeight[0]][compWidth[0]];
float Cr1[][] = new float[compHeight[0]][compWidth[0]];
float Cb1[][] = new float[compHeight[0]][compWidth[0]];
// float Cb2[][] = new float[compHeight[1]][compWidth[1]];
// float Cr2[][] = new float[compHeight[2]][compWidth[2]];
int index = 0;
for (y = 0; y < imageHeight; ++y) {
for (x = 0; x < imageWidth; ++x) {
r = ((values[index] >> 16) & 0xff);
g = ((values[index] >> 8) & 0xff);
b = (values[index] & 0xff);
// The following three lines are a more correct color conversion but
// the current conversion technique is sufficient and results in a
// higher
// compression rate.
// Y[y][x] = 16 + (float)(0.8588*(0.299 * (float)r + 0.587 * (float)g +
// 0.114 * (float)b ));
// Cb1[y][x] = 128 + (float)(0.8784*(-0.16874 * (float)r - 0.33126 *
// (float)g + 0.5 * (float)b));
// Cr1[y][x] = 128 + (float)(0.8784*(0.5 * (float)r - 0.41869 * (float)g
// - 0.08131 * (float)b));
Y[y][x] = (float) ((0.299 * r + 0.587 * g + 0.114 * b));
Cb1[y][x] = 128 + (float) ((-0.16874 * r - 0.33126 * g + 0.5 * b));
Cr1[y][x] = 128 + (float) ((0.5 * r - 0.41869 * g - 0.08131 * b));
index++;
}
}
// Need a way to set the H and V sample factors before allowing
// downsampling.
// For now (04/04/98) downsampling must be hard coded.
// Until a better downsampler is implemented, this will not be done.
// Downsampling is currently supported. The downsampling method here
// is a simple box filter.
Components[0] = Y;
// Cb2 = DownSample(Cb1, 1);
Components[1] = Cb1;
// Cr2 = DownSample(Cr1, 2);
Components[2] = Cr1;
}
float[][] DownSample(float[][] C, int comp) {
int inrow, incol;
int outrow, outcol;
float output[][];
int bias;
inrow = 0;
incol = 0;
output = new float[compHeight[comp]][compWidth[comp]];
for (outrow = 0; outrow < compHeight[comp]; outrow++) {
bias = 1;
for (outcol = 0; outcol < compWidth[comp]; outcol++) {
output[outrow][outcol] = (C[inrow][incol++] + C[inrow++][incol--] + C[inrow][incol++]
+ C[inrow--][incol++] + bias)
/ (float) 4.0;
bias ^= 3;
}
inrow += 2;
incol = 0;
}
return output;
}
}
]]>