jpegencoder.java

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            System.out.println("IO Error: " + e.getMessage());
        }
    }

    void WriteArray(byte[] data, BufferedOutputStream out) {
        int i;
        int length;

        try {
            length = (((int) (data[2] & 0xFF)) << 8) + (int) (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] = (double) ((double) 1.0 / ((double) quantum_luminance[index] * AANscaleFactor[i] * AANscaleFactor[j] * (double) 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] = (double) ((double) 1.0 / ((double) quantum_chrominance[index] * AANscaleFactor[i] * AANscaleFactor[j] * (double) 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];
        double tmp0;
        double tmp1;
        double tmp2;
        double tmp3;
        double tmp4;
        double tmp5;
        double tmp6;
        double tmp7;
        double tmp10;
        double tmp11;
        double tmp12;
        double tmp13;
        double z1;
        double z2;
        double z3;
        double z4;
        double z5;
        double z11;
        double z13;
        int i;
        int j;
        int v;
        int u;
        int x;
        int 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] += (((double) input[x][y]) * Math.cos(((double) ((2 * x) +
                            1) * (double) u * Math.PI) / (double) 16) * Math.cos(((double) ((2 * y) +
                            1) * (double) v * Math.PI) / (double) 16));
                    }
                }

                output[v][u] *= ((double) (0.25) * ((u == 0)
                ? ((double) 1.0 / Math.sqrt(2)) : (double) 1.0) * ((v == 0)
                ? ((double) 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;
        double tmp1;
        double tmp2;
        double tmp3;
        double tmp4;
        double tmp5;
        double tmp6;
        double tmp7;
        double tmp10;
        double tmp11;
        double tmp12;
        double tmp13;
        double z1;
        double z2;
        double z3;
        double z4;
        double z5;
        double z11;
        double z13;