fxt1.c

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/*
 * FXT1 codec
 * Version:  1.1
 *
 * Copyright (C) 2004  Daniel Borca   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * DANIEL BORCA BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


#include <stdlib.h>
#include <string.h>

#include "types.h"
#include "internal.h"
#include "fxt1.h"


/***************************************************************************\
 * FXT1 encoder
 *
 * The encoder was built by reversing the decoder,
 * and is vaguely based on Texus2 by 3dfx. Note that this code
 * is merely a proof of concept, since it is highly UNoptimized;
 * moreover, it is sub-optimal due to initial conditions passed
 * to Lloyd's algorithm (the interpolation modes are even worse).
\***************************************************************************/


#define MAX_COMP 4 /* ever needed maximum number of components in texel */
#define MAX_VECT 4 /* ever needed maximum number of base vectors to find */
#define N_TEXELS 32 /* number of texels in a block (always 32) */
#define LL_N_REP 50 /* number of iterations in lloyd's vq */
#define LL_RMS_D 10 /* fault tolerance (maximum delta) */
#define LL_RMS_E 255 /* fault tolerance (maximum error) */
#define ALPHA_TS 2 /* alpha threshold: (255 - ALPHA_TS) deemed opaque */
#define ISTBLACK(v) (*((dword *)(v)) == 0)
#define COPY_4UBV(DST, SRC) *((dword *)(DST)) = *((dword *)(SRC))


static int
fxt1_bestcol (float vec[][MAX_COMP], int nv,
          byte input[MAX_COMP], int nc)
{
    int i, j, best = -1;
    float err = 1e9; /* big enough */

    for (j = 0; j < nv; j++) {
    float e = 0.0F;
    for (i = 0; i < nc; i++) {
        e += (vec[j][i] - input[i]) * (vec[j][i] - input[i]);
    }
    if (e < err) {
        err = e;
        best = j;
    }
    }

    return best;
}


static int
fxt1_worst (float vec[MAX_COMP],
        byte input[N_TEXELS][MAX_COMP], int nc, int n)
{
    int i, k, worst = -1;
    float err = -1.0F; /* small enough */

    for (k = 0; k < n; k++) {
    float e = 0.0F;
    for (i = 0; i < nc; i++) {
        e += (vec[i] - input[k][i]) * (vec[i] - input[k][i]);
    }
    if (e > err) {
        err = e;
        worst = k;
    }
    }

    return worst;
}


static int
fxt1_variance (double variance[MAX_COMP],
           byte input[N_TEXELS][MAX_COMP], int nc, int n)
{
    int i, k, best = 0;
    dword sx, sx2;
    double var, maxvar = -1; /* small enough */
    double teenth = 1.0 / n;

    for (i = 0; i < nc; i++) {
    sx = sx2 = 0;
    for (k = 0; k < n; k++) {
        int t = input[k][i];
        sx += t;
        sx2 += t * t;
    }
    var = sx2 * teenth - sx * sx * teenth * teenth;
    if (maxvar < var) {
        maxvar = var;
        best = i;
    }
    if (variance) {
        variance[i] = var;
    }
    }

    return best;
}


static int
fxt1_choose (float vec[][MAX_COMP], int nv,
         byte input[N_TEXELS][MAX_COMP], int nc, int n)
{
#if 0
    /* Choose colors from a grid.
     */
    int i, j;

    for (j = 0; j < nv; j++) {
    int m = j * (n - 1) / (nv - 1);
    for (i = 0; i < nc; i++) {
        vec[j][i] = input[m][i];
    }
    }
#else
    /* Our solution here is to find the darkest and brightest colors in
     * the 8x4 tile and use those as the two representative colors.
     * There are probably better algorithms to use (histogram-based).
     */
    int i, j, k;
    int minSum = 2000; /* big enough */
    int maxSum = -1; /* small enough */
    int minCol = 0; /* phoudoin: silent compiler! */
    int maxCol = 0; /* phoudoin: silent compiler! */

    struct {
    int flag;
    dword key;
    int freq;
    int idx;
    } hist[N_TEXELS];
    int lenh = 0;

    memset(hist, 0, sizeof(hist));

    for (k = 0; k < n; k++) {
    int l;
    dword key = 0;
    int sum = 0;
    for (i = 0; i < nc; i++) {
        key <<= 8;
        key |= input[k][i];
        sum += input[k][i];
    }
    for (l = 0; l < n; l++) {
        if (!hist[l].flag) {
        /* alloc new slot */
        hist[l].flag = !0;
        hist[l].key = key;
        hist[l].freq = 1;
        hist[l].idx = k;
        lenh = l + 1;
        break;
        } else if (hist[l].key == key) {
        hist[l].freq++;
        break;
        }
    }
    if (minSum > sum) {
        minSum = sum;
        minCol = k;
    }
    if (maxSum < sum) {
        maxSum = sum;
        maxCol = k;
    }
    }

    if (lenh <= nv) {
    for (j = 0; j < lenh; j++) {
        for (i = 0; i < nc; i++) {
        vec[j][i] = (float)input[hist[j].idx][i];
        }
    }
    for (; j < nv; j++) {
        for (i = 0; i < nc; i++) {
        vec[j][i] = vec[0][i];
        }
    }
    return 0;
    }

    for (j = 0; j < nv; j++) {
    for (i = 0; i < nc; i++) {
        vec[j][i] = ((nv - 1 - j) * input[minCol][i] + j * input[maxCol][i] + (nv - 1) / 2) / (float)(nv - 1);
    }
    }
#endif

    return !0;
}


static int
fxt1_lloyd (float vec[][MAX_COMP], int nv,
        byte input[N_TEXELS][MAX_COMP], int nc, int n)
{
    /* Use the generalized lloyd's algorithm for VQ:
     *     find 4 color vectors.
     *
     *     for each sample color
     *         sort to nearest vector.
     *
     *     replace each vector with the centroid of it's matching colors.
     *
     *     repeat until RMS doesn't improve.
     *
     *     if a color vector has no samples, or becomes the same as another
     *     vector, replace it with the color which is farthest from a sample.
     *
     * vec[][MAX_COMP]           initial vectors and resulting colors
     * nv                        number of resulting colors required
     * input[N_TEXELS][MAX_COMP] input texels
     * nc                        number of components in input / vec
     * n                         number of input samples
     */

    int sum[MAX_VECT][MAX_COMP]; /* used to accumulate closest texels */
    int cnt[MAX_VECT]; /* how many times a certain vector was chosen */
    float error, lasterror = 1e9;

    int i, j, k, rep;

    /* the quantizer */
    for (rep = 0; rep < LL_N_REP; rep++) {
    /* reset sums & counters */
    for (j = 0; j < nv; j++) {
        for (i = 0; i < nc; i++) {
        sum[j][i] = 0;
        }
        cnt[j] = 0;
    }
    error = 0;

    /* scan whole block */
    for (k = 0; k < n; k++) {
#if 1
        int best = -1;
        float err = 1e9; /* big enough */
        /* determine best vector */
        for (j = 0; j < nv; j++) {
        float e = (vec[j][0] - input[k][0]) * (vec[j][0] - input[k][0]) +
              (vec[j][1] - input[k][1]) * (vec[j][1] - input[k][1]) +
              (vec[j][2] - input[k][2]) * (vec[j][2] - input[k][2]);
        if (nc == 4) {
            e += (vec[j][3] - input[k][3]) * (vec[j][3] - input[k][3]);
        }
        if (e < err) {
            err = e;
            best = j;
        }
        }
#else
        int best = fxt1_bestcol(vec, nv, input[k], nc, &err);
#endif
        /* add in closest color */
        for (i = 0; i < nc; i++) {
        sum[best][i] += input[k][i];
        }
        /* mark this vector as used */
        cnt[best]++;
        /* accumulate error */
        error += err;
    }

    /* check RMS */
    if ((error < LL_RMS_E) ||
        ((error < lasterror) && ((lasterror - error) < LL_RMS_D))) {
        return !0; /* good match */
    }
    lasterror = error;

    /* move each vector to the barycenter of its closest colors */
    for (j = 0; j < nv; j++) {
        if (cnt[j]) {
        float div = 1.0F / cnt[j];
        for (i = 0; i < nc; i++) {
            vec[j][i] = div * sum[j][i];
        }
        } else {
        /* this vec has no samples or is identical with a previous vec */
        int worst = fxt1_worst(vec[j], input, nc, n);
        for (i = 0; i < nc; i++) {
            vec[j][i] = input[worst][i];
        }
        }
    }
    }

    return 0; /* could not converge fast enough */
}


static void
fxt1_quantize_CHROMA (dword *cc,
              byte input[N_TEXELS][MAX_COMP])
{
    const int n_vect = 4; /* 4 base vectors to find */
    const int n_comp = 3; /* 3 components: R, G, B */
    float vec[MAX_VECT][MAX_COMP];
    int i, j, k;
    qword hi; /* high quadword */
    dword lohi, lolo; /* low quadword: hi dword, lo dword */

    if (fxt1_choose(vec, n_vect, input, n_comp, N_TEXELS) != 0) {
    fxt1_lloyd(vec, n_vect, input, n_comp, N_TEXELS);
    }

    Q_MOV32(hi, 4); /* cc-chroma = "010" + unused bit */
    for (j = n_vect - 1; j >= 0; j--) {
    for (i = 0; i < n_comp; i++) {
        /* add in colors */
        Q_SHL(hi, 5);
        Q_OR32(hi, (dword)(vec[j][i] / 8.0F));
    }
    }
    ((qword *)cc)[1] = hi;

    lohi = lolo = 0;
    /* right microtile */
    for (k = N_TEXELS - 1; k >= N_TEXELS / 2; k--) {
    lohi <<= 2;
    lohi |= fxt1_bestcol(vec, n_vect, input[k], n_comp);
    }
    /* left microtile */
    for (; k >= 0; k--) {
    lolo <<= 2;
    lolo |= fxt1_bestcol(vec, n_vect, input[k], n_comp);
    }
    cc[1] = lohi;
    cc[0] = lolo;
}


static void
fxt1_quantize_ALPHA0 (dword *cc,
              byte input[N_TEXELS][MAX_COMP],
              byte reord[N_TEXELS][MAX_COMP], int n)
{
    const int n_vect = 3; /* 3 base vectors to find */
    const int n_comp = 4; /* 4 components: R, G, B, A */
    float vec[MAX_VECT][MAX_COMP];
    int i, j, k;
    qword hi; /* high quadword */
    dword lohi, lolo; /* low quadword: hi dword, lo dword */

    /* the last vector indicates zero */
    for (i = 0; i < n_comp; i++) {
    vec[n_vect][i] = 0;
    }

    /* the first n texels in reord are guaranteed to be non-zero */
    if (fxt1_choose(vec, n_vect, reord, n_comp, n) != 0) {
    fxt1_lloyd(vec, n_vect, reord, n_comp, n);
    }

    Q_MOV32(hi, 6); /* alpha = "011" + lerp = 0 */
    for (j = n_vect - 1; j >= 0; j--) {
    /* add in alphas */
    Q_SHL(hi, 5);
    Q_OR32(hi, (dword)(vec[j][ACOMP] / 8.0F));
    }
    for (j = n_vect - 1; j >= 0; j--) {
    for (i = 0; i < n_comp - 1; i++) {
        /* add in colors */
        Q_SHL(hi, 5);
        Q_OR32(hi, (dword)(vec[j][i] / 8.0F));
    }
    }
    ((qword *)cc)[1] = hi;

    lohi = lolo = 0;
    /* right microtile */
    for (k = N_TEXELS - 1; k >= N_TEXELS / 2; k--) {
    lohi <<= 2;
    lohi |= fxt1_bestcol(vec, n_vect + 1, input[k], n_comp);
    }
    /* left microtile */
    for (; k >= 0; k--) {
    lolo <<= 2;
    lolo |= fxt1_bestcol(vec, n_vect + 1, input[k], n_comp);
    }
    cc[1] = lohi;
    cc[0] = lolo;
}


static void
fxt1_quantize_ALPHA1 (dword *cc,
              byte input[N_TEXELS][MAX_COMP])
{
    const int n_vect = 3; /* highest vector number in each microtile */
    const int n_comp = 4; /* 4 components: R, G, B, A */
    float vec[1 + 1 + 1][MAX_COMP]; /* 1.5 extrema for each sub-block */
    float b, iv[MAX_COMP]; /* interpolation vector */
    int i, j, k;
    qword hi; /* high quadword */
    dword lohi, lolo; /* low quadword: hi dword, lo dword */

    int minSum;
    int maxSum;
    int minColL = 0, maxColL = 0;
    int minColR = 0, maxColR = 0;
    int sumL = 0, sumR = 0;

    /* Our solution here is to find the darkest and brightest colors in
     * the 4x4 tile and use those as the two representative colors.
     * There are probably better algorithms to use (histogram-based).
     */
    minSum = 2000; /* big enough */
    maxSum = -1; /* small enough */
    for (k = 0; k < N_TEXELS / 2; k++) {
    int sum = 0;
    for (i = 0; i < n_comp; i++) {
        sum += input[k][i];
    }
    if (minSum > sum) {
        minSum = sum;
        minColL = k;
    }
    if (maxSum < sum) {
        maxSum = sum;
        maxColL = k;
    }
    sumL += sum;
    }
    minSum = 2000; /* big enough */
    maxSum = -1; /* small enough */
    for (; k < N_TEXELS; k++) {
    int sum = 0;
    for (i = 0; i < n_comp; i++) {
        sum += input[k][i];
    }
    if (minSum > sum) {
        minSum = sum;
        minColR = k;
    }
    if (maxSum < sum) {
        maxSum = sum;
        maxColR = k;
    }
    sumR += sum;
    }

    /* choose the common vector (yuck!) */
    {
    int j1, j2;
    int v1 = 0, v2 = 0;
    float err = 1e9; /* big enough */
    float tv[2 * 2][MAX_COMP]; /* 2 extrema for each sub-block */
    for (i = 0; i < n_comp; i++) {
        tv[0][i] = input[minColL][i];
        tv[1][i] = input[maxColL][i];
        tv[2][i] = input[minColR][i];
        tv[3][i] = input[maxColR][i];
    }
    for (j1 = 0; j1 < 2; j1++) {
        for (j2 = 2; j2 < 4; j2++) {
        float e = 0.0F;
        for (i = 0; i < n_comp; i++) {
            e += (tv[j1][i] - tv[j2][i]) * (tv[j1][i] - tv[j2][i]);
        }
        if (e < err) {
            err = e;
            v1 = j1;
            v2 = j2;
        }
        }
    }
    for (i = 0; i < n_comp; i++) {
        vec[0][i] = tv[1 - v1][i];
        vec[1][i] = (tv[v1][i] * sumL + tv[v2][i] * sumR) / (sumL + sumR);
        vec[2][i] = tv[5 - v2][i];
    }
    }

    /* left microtile */
    cc[0] = 0;
    if (minColL != maxColL) {
    /* compute interpolation vector */
    MAKEIVEC(n_vect, n_comp, iv, b, vec[0], vec[1]);

    /* add in texels */
    lolo = 0;
    for (k = N_TEXELS / 2 - 1; k >= 0; k--) {
        int texel;
        /* interpolate color */
        CALCCDOT(texel, n_vect, n_comp, iv, b, input[k]);
        /* add in texel */
        lolo <<= 2;
        lolo |= texel;
    }

    cc[0] = lolo;
    }

    /* right microtile */
    cc[1] = 0;
    if (minColR != maxColR) {
    /* compute interpolation vector */
    MAKEIVEC(n_vect, n_comp, iv, b, vec[2], vec[1]);

    /* add in texels */
    lohi = 0;
    for (k = N_TEXELS - 1; k >= N_TEXELS / 2; k--) {
        int texel;
        /* interpolate color */
        CALCCDOT(texel, n_vect, n_comp, iv, b, input[k]);
        /* add in texel */
        lohi <<= 2;
        lohi |= texel;
    }

    cc[1] = lohi;
    }

    Q_MOV32(hi, 7); /* alpha = "011" + lerp = 1 */
    for (j = n_vect - 1; j >= 0; j--) {
    /* add in alphas */
    Q_SHL(hi, 5);
    Q_OR32(hi, (dword)(vec[j][ACOMP] / 8.0F));
    }
    for (j = n_vect - 1; j >= 0; j--) {
    for (i = 0; i < n_comp - 1; i++) {
        /* add in colors */
        Q_SHL(hi, 5);
        Q_OR32(hi, (dword)(vec[j][i] / 8.0F));
    }
    }
    ((qword *)cc)[1] = hi;
}


static void
fxt1_quantize_HI (dword *cc,
          byte input[N_TEXELS][MAX_COMP],
          byte reord[N_TEXELS][MAX_COMP], int n)
{
    const int n_vect = 6; /* highest vector number */
    const int n_comp = 3; /* 3 components: R, G, B */
    float b = 0.0F;       /* phoudoin: silent compiler! */
    float iv[MAX_COMP];   /* interpolation vector */
    int i, k;
    dword hihi; /* high quadword: hi dword */

    int minSum = 2000; /* big enough */
    int maxSum = -1; /* small enough */
    int minCol = 0; /* phoudoin: silent compiler! */
    int maxCol = 0; /* phoudoin: silent compiler! */

    /* Our solution here is to find the darkest and brightest colors in
     * the 8x4 tile and use those as the two representative colors.
     * There are probably better algorithms to use (histogram-based).
     */
    for (k = 0; k < n; k++) {
    int sum = 0;
    for (i = 0; i < n_comp; i++) {
        sum += reord[k][i];
    }
    if (minSum > sum) {
        minSum = sum;
        minCol = k;
    }
    if (maxSum < sum) {
        maxSum = sum;
        maxCol = k;
    }
    }

    hihi = 0; /* cc-hi = "00" */
    for (i = 0; i < n_comp; i++) {
    /* add in colors */
    hihi <<= 5;
    hihi |= reord[maxCol][i] >> 3;
    }
    for (i = 0; i < n_comp; i++) {
    /* add in colors */
    hihi <<= 5;
    hihi |= reord[minCol][i] >> 3;
    }
    cc[3] = hihi;
    cc[0] = cc[1] = cc[2] = 0;

    /* compute interpolation vector */
    if (minCol != maxCol) {
    MAKEIVEC(n_vect, n_comp, iv, b, reord[minCol], reord[maxCol]);
    }

    /* add in texels */
    for (k = N_TEXELS - 1; k >= 0; k--) {
    int t = k * 3;
    dword *kk = (dword *)((byte *)cc + t / 8);
    int texel = n_vect + 1; /* transparent black */

    if (!ISTBLACK(input[k])) {
        if (minCol != maxCol) {
        /* interpolate color */
        CALCCDOT(texel, n_vect, n_comp, iv, b, input[k]);
        /* add in texel */
        kk[0] |= texel << (t & 7);
        }
    } else {
        /* add in texel */
        kk[0] |= texel << (t & 7);
    }
    }
}


static void
fxt1_quantize_MIXED1 (dword *cc,
              byte input[N_TEXELS][MAX_COMP])
{
    const int n_vect = 2; /* highest vector number in each microtile */
    const int n_comp = 3; /* 3 components: R, G, B */
    byte vec[2 * 2][MAX_COMP]; /* 2 extrema for each sub-block */
    float b, iv[MAX_COMP]; /* interpolation vector */
    int i, j, k;
    qword hi; /* high quadword */
    dword lohi, lolo; /* low quadword: hi dword, lo dword */

    int minSum;
    int maxSum;
    int minColL = 0, maxColL = -1;
    int minColR = 0, maxColR = -1;

    /* Our solution here is to find the darkest and brightest colors in
     * the 4x4 tile and use those as the two representative colors.
     * There are probably better algorithms to use (histogram-based).
     */
    minSum = 2000; /* big enough */
    maxSum = -1; /* small enough */
    for (k = 0; k < N_TEXELS / 2; k++) {
    if (!ISTBLACK(input[k])) {
        int sum = 0;
        for (i = 0; i < n_comp; i++) {
        sum += input[k][i];
        }
        if (minSum > sum) {
        minSum = sum;
        minColL = k;
        }
        if (maxSum < sum) {
        maxSum = sum;
        maxColL = k;
        }
    }
    }
    minSum = 2000; /* big enough */
    maxSum = -1; /* small enough */
    for (; k < N_TEXELS; k++) {
    if (!ISTBLACK(input[k])) {
        int sum = 0;
        for (i = 0; i < n_comp; i++) {
        sum += input[k][i];
        }
        if (minSum > sum) {
        minSum = sum;
        minColR = k;
        }
        if (maxSum < sum) {
        maxSum = sum;
        maxColR = k;
        }
    }
    }

    /* left microtile */
    if (maxColL == -1) {
    /* all transparent black */
    cc[0] = ~0UL;
    for (i = 0; i < n_comp; i++) {
        vec[0][i] = 0;
        vec[1][i] = 0;
    }
    } else {
    cc[0] = 0;
    for (i = 0; i < n_comp; i++) {
        vec[0][i] = input[minColL][i];
        vec[1][i] = input[maxColL][i];
    }
    if (minColL != maxColL) {
        /* compute interpolation vector */
        MAKEIVEC(n_vect, n_comp, iv, b, vec[0], vec[1]);

        /* add in texels */
        lolo = 0;
        for (k = N_TEXELS / 2 - 1; k >= 0; k--) {
        int texel = n_vect + 1; /* transparent black */
        if (!ISTBLACK(input[k])) {
            /* interpolate color */
            CALCCDOT(texel, n_vect, n_comp, iv, b, input[k]);
        }
        /* add in texel */
        lolo <<= 2;
        lolo |= texel;
        }
        cc[0] = lolo;
    }
    }

    /* right microtile */
    if (maxColR == -1) {
    /* all transparent black */
    cc[1] = ~0UL;
    for (i = 0; i < n_comp; i++) {
        vec[2][i] = 0;
        vec[3][i] = 0;
    }
    } else {
    cc[1] = 0;
    for (i = 0; i < n_comp; i++) {
        vec[2][i] = input[minColR][i];
        vec[3][i] = input[maxColR][i];
    }
    if (minColR != maxColR) {
        /* compute interpolation vector */
        MAKEIVEC(n_vect, n_comp, iv, b, vec[2], vec[3]);

        /* add in texels */
        lohi = 0;
        for (k = N_TEXELS - 1; k >= N_TEXELS / 2; k--) {
        int texel = n_vect + 1; /* transparent black */
        if (!ISTBLACK(input[k])) {
            /* interpolate color */
            CALCCDOT(texel, n_vect, n_comp, iv, b, input[k]);
        }
        /* add in texel */
        lohi <<= 2;
        lohi |= texel;
        }
        cc[1] = lohi;
    }
    }

    Q_MOV32(hi, 9 | (vec[3][GCOMP] & 4) | ((vec[1][GCOMP] >> 1) & 2)); /* chroma = "1" */
    for (j = 2 * 2 - 1; j >= 0; j--) {
    for (i = 0; i < n_comp; i++) {
        /* add in colors */
        Q_SHL(hi, 5);
        Q_OR32(hi, vec[j][i] >> 3);
    }
    }
    ((qword *)cc)[1] = hi;
}


static void
fxt1_quantize_MIXED0 (dword *cc,
              byte input[N_TEXELS][MAX_COMP])
{
    const int n_vect = 3; /* highest vector number in each microtile */
    const int n_comp = 3; /* 3 components: R, G, B */
    byte vec[2 * 2][MAX_COMP]; /* 2 extrema for each sub-block */
    float b, iv[MAX_COMP]; /* interpolation vector */
    int i, j, k;
    qword hi; /* high quadword */
    dword lohi, lolo; /* low quadword: hi dword, lo dword */

    int minColL = 0, maxColL = 0;
    int minColR = 0, maxColR = 0;
#if 0
    int minSum;
    int maxSum;

    /* Our solution here is to find the darkest and brightest colors in
     * the 4x4 tile and use those as the two representative colors.
     * There are probably better algorithms to use (histogram-based).
     */
    minSum = 2000; /* big enough */
    maxSum = -1; /* small enough */
    for (k = 0; k < N_TEXELS / 2; k++) {
    int sum = 0;
    for (i = 0; i < n_comp; i++) {
        sum += input[k][i];
    }
    if (minSum > sum) {
        minSum = sum;
        minColL = k;
    }
    if (maxSum < sum) {
        maxSum = sum;
        maxColL = k;
    }
    }
    minSum = 2000; /* big enough */
    maxSum = -1; /* small enough */
    for (; k < N_TEXELS; k++) {
    int sum = 0;
    for (i = 0; i < n_comp; i++) {
        sum += input[k][i];
    }
    if (minSum > sum) {
        minSum = sum;
        minColR = k;
    }
    if (maxSum < sum) {
        maxSum = sum;
        maxColR = k;
    }
    }
#else
    int minVal;
    int maxVal;
    int maxVarL = fxt1_variance(NULL, input, n_comp, N_TEXELS / 2);
    int maxVarR = fxt1_variance(NULL, &input[N_TEXELS / 2], n_comp, N_TEXELS / 2);

    /* Scan the channel with max variance for lo & hi
     * and use those as the two representative colors.
     */
    minVal = 2000; /* big enough */
    maxVal = -1; /* small enough */
    for (k = 0; k < N_TEXELS / 2; k++) {
    int t = input[k][maxVarL];
    if (minVal > t) {
        minVal = t;
        minColL = k;
    }
    if (maxVal < t) {
        maxVal = t;
        maxColL = k;
    }
    }
    minVal = 2000; /* big enough */
    maxVal = -1; /* small enough */
    for (; k < N_TEXELS; k++) {
    int t = input[k][maxVarR];
    if (minVal > t) {
        minVal = t;
        minColR = k;
    }
    if (maxVal < t) {
        maxVal = t;
        maxColR = k;
    }
    }
#endif

    /* left microtile */
    cc[0] = 0;
    for (i = 0; i < n_comp; i++) {
    vec[0][i] = input[minColL][i];
    vec[1][i] = input[maxColL][i];
    }
    if (minColL != maxColL) {
    /* compute interpolation vector */
    MAKEIVEC(n_vect, n_comp, iv, b, vec[0], vec[1]);

    /* add in texels */
    lolo = 0;
    for (k = N_TEXELS / 2 - 1; k >= 0; k--) {
        int texel;
        /* interpolate color */
        CALCCDOT(texel, n_vect, n_comp, iv, b, input[k]);
        /* add in texel */
        lolo <<= 2;
        lolo |= texel;
    }

    /* funky encoding for LSB of green */
    if ((int)((lolo >> 1) & 1) != (((vec[1][GCOMP] ^ vec[0][GCOMP]) >> 2) & 1)) {
        for (i = 0; i < n_comp; i++) {
        vec[1][i] = input[minColL][i];
        vec[0][i] = input[maxColL][i];
        }
        lolo = ~lolo;
    }

    cc[0] = lolo;
    }

    /* right microtile */
    cc[1] = 0;
    for (i = 0; i < n_comp; i++) {
    vec[2][i] = input[minColR][i];
    vec[3][i] = input[maxColR][i];
    }
    if (minColR != maxColR) {
    /* compute interpolation vector */
    MAKEIVEC(n_vect, n_comp, iv, b, vec[2], vec[3]);

    /* add in texels */
    lohi = 0;
    for (k = N_TEXELS - 1; k >= N_TEXELS / 2; k--) {
        int texel;
        /* interpolate color */
        CALCCDOT(texel, n_vect, n_comp, iv, b, input[k]);
        /* add in texel */
        lohi <<= 2;
        lohi |= texel;
    }

    /* funky encoding for LSB of green */
    if ((int)((lohi >> 1) & 1) != (((vec[3][GCOMP] ^ vec[2][GCOMP]) >> 2) & 1)) {
        for (i = 0; i < n_comp; i++) {
        vec[3][i] = input[minColR][i];
        vec[2][i] = input[maxColR][i];
        }
        lohi = ~lohi;
    }

    cc[1] = lohi;
    }

    Q_MOV32(hi, 8 | (vec[3][GCOMP] & 4) | ((vec[1][GCOMP] >> 1) & 2)); /* chroma = "1" */
    for (j = 2 * 2 - 1; j >= 0; j--) {
    for (i = 0; i < n_comp; i++) {
        /* add in colors */
        Q_SHL(hi, 5);
        Q_OR32(hi, vec[j][i] >> 3);
    }
    }
    ((qword *)cc)[1] = hi;
}


static void
fxt1_quantize (dword *cc, const byte *lines[], int comps)
{
    int trualpha;
    byte reord[N_TEXELS][MAX_COMP];

    byte input[N_TEXELS][MAX_COMP];
    int i, k, l;

    if (comps == 3) {
    /* make the whole block opaque */
    memset(input, -1, sizeof(input));
    }

    /* 8 texels each line */
    for (l = 0; l < 4; l++) {
    for (k = 0; k < 4; k++) {
        for (i = 0; i < comps; i++) {
        input[k + l * 4][i] = *lines[l]++;
        }
    }
    for (; k < 8; k++) {
        for (i = 0; i < comps; i++) {
        input[k + l * 4 + 12][i] = *lines[l]++;
        }
    }
    }

    /* block layout:
     * 00, 01, 02, 03, 08, 09, 0a, 0b
     * 10, 11, 12, 13, 18, 19, 1a, 1b
     * 04, 05, 06, 07, 0c, 0d, 0e, 0f
     * 14, 15, 16, 17, 1c, 1d, 1e, 1f
     */

    /* [dBorca]
     * stupidity flows forth from this
     */
    l = N_TEXELS;
    trualpha = 0;
    if (comps == 4) {
    /* skip all transparent black texels */
    l = 0;
    for (k = 0; k < N_TEXELS; k++) {
        /* test all components against 0 */
        if (!ISTBLACK(input[k])) {
        /* texel is not transparent black */
        COPY_4UBV(reord[l], input[k]);
        if (reord[l][ACOMP] < (255 - ALPHA_TS)) {
            /* non-opaque texel */
            trualpha = !0;
        }
        l++;
        }
    }
    }

#if 0
    if (trualpha) {
    fxt1_quantize_ALPHA0(cc, input, reord, l);
    } else if (l == 0) {
    cc[0] = cc[1] = cc[2] = -1;
    cc[3] = 0;
    } else if (l < N_TEXELS) {
    fxt1_quantize_HI(cc, input, reord, l);
    } else {
    fxt1_quantize_CHROMA(cc, input);
    }
    (void)fxt1_quantize_ALPHA1;
    (void)fxt1_quantize_MIXED1;
    (void)fxt1_quantize_MIXED0;
#else
    if (trualpha) {
    fxt1_quantize_ALPHA1(cc, input);
    } else if (l == 0) {
    cc[0] = cc[1] = cc[2] = ~0UL;
    cc[3] = 0;
    } else if (l < N_TEXELS) {
    fxt1_quantize_MIXED1(cc, input);
    } else {
    fxt1_quantize_MIXED0(cc, input);
    }
    (void)fxt1_quantize_ALPHA0;
    (void)fxt1_quantize_HI;
    (void)fxt1_quantize_CHROMA;
#endif
}


TAPI int TAPIENTRY
fxt1_encode (int width, int height, int comps,
         const void *source, int srcRowStride,
         void *dest, int destRowStride)
{
    int x, y;
    const byte *data;
    dword *encoded = (dword *)dest;
    void *newSource = NULL;

    /* Replicate image if width is not M8 or height is not M4 */
    if ((width & 7) | (height & 3)) {
    int newWidth = (width + 7) & ~7;
    int newHeight = (height + 3) & ~3;
    newSource = malloc(comps * newWidth * newHeight * sizeof(byte *));
    _mesa_upscale_teximage2d(width, height, newWidth, newHeight,
                 comps, (const byte *)source,
                 srcRowStride, (byte *)newSource);
    source = newSource;
    width = newWidth;
    height = newHeight;
    srcRowStride = comps * newWidth;
    }

    data = (const byte *)source;
    destRowStride = (destRowStride - width * 2) / 4;
    for (y = 0; y < height; y += 4) {
    unsigned int offs = 0 + (y + 0) * srcRowStride;
    for (x = 0; x < width; x += 8) {
        const byte *lines[4];
        lines[0] = &data[offs];
        lines[1] = lines[0] + srcRowStride;
        lines[2] = lines[1] + srcRowStride;
        lines[3] = lines[2] + srcRowStride;
        offs += 8 * comps;
        fxt1_quantize(encoded, lines, comps);
        /* 128 bits per 8x4 block */
        encoded += 4;
    }
    encoded += destRowStride;
    }

    if (newSource != NULL) {
    free(newSource);
    }

    return 0;
}


/***************************************************************************\
 * FXT1 decoder
 *
 * The decoder is based on GL_3DFX_texture_compression_FXT1
 * specification and serves as a concept for the encoder.
\***************************************************************************/


/* lookup table for scaling 5 bit colors up to 8 bits */
static const byte _rgb_scale_5[] = {
    0,   8,   16,  25,  33,  41,  49,  58,
    66,  74,  82,  90,  99,  107, 115, 123,
    132, 140, 148, 156, 165, 173, 181, 189,
    197, 206, 214, 222, 230, 239, 247, 255
};

/* lookup table for scaling 6 bit colors up to 8 bits */
static const byte _rgb_scale_6[] = {
    0,   4,   8,   12,  16,  20,  24,  28,
    32,  36,  40,  45,  49,  53,  57,  61,
    65,  69,  73,  77,  81,  85,  89,  93,
    97,  101, 105, 109, 113, 117, 121, 125,
    130, 134, 138, 142, 146, 150, 154, 158,
    162, 166, 170, 174, 178, 182, 186, 190,
    194, 198, 202, 206, 210, 215, 219, 223,
    227, 231, 235, 239, 243, 247, 251, 255
};


#define CC_SEL(cc, which) (((dword *)(cc))[(which) / 32] >> ((which) & 31))
#define UP5(c) _rgb_scale_5[(c) & 31]
#define UP6(c, b) _rgb_scale_6[(((c) & 31) << 1) | ((b) & 1)]
#define LERP(n, t, c0, c1) (((n) - (t)) * (c0) + (t) * (c1) + (n) / 2) / (n)
#define ZERO_4UBV(v) *((dword *)(v)) = 0


static void
fxt1_decode_1HI (const byte *code, int t, byte *rgba)
{
    const dword *cc;

    t *= 3;
    cc = (const dword *)(code + t / 8);
    t = (cc[0] >> (t & 7)) & 7;

    if (t == 7) {
    ZERO_4UBV(rgba);
    } else {
    cc = (const dword *)(code + 12);
    if (t == 0) {
        rgba[BCOMP] = UP5(CC_SEL(cc, 0));
        rgba[GCOMP] = UP5(CC_SEL(cc, 5));
        rgba[RCOMP] = UP5(CC_SEL(cc, 10));
    } else if (t == 6) {
        rgba[BCOMP] = UP5(CC_SEL(cc, 15));
        rgba[GCOMP] = UP5(CC_SEL(cc, 20));
        rgba[RCOMP] = UP5(CC_SEL(cc, 25));
    } else {
        rgba[BCOMP] = LERP(6, t, UP5(CC_SEL(cc, 0)), UP5(CC_SEL(cc, 15)));
        rgba[GCOMP] = LERP(6, t, UP5(CC_SEL(cc, 5)), UP5(CC_SEL(cc, 20)));
        rgba[RCOMP] = LERP(6, t, UP5(CC_SEL(cc, 10)), UP5(CC_SEL(cc, 25)));
    }
    rgba[ACOMP] = 255;
    }
}


static void
fxt1_decode_1CHROMA (const byte *code, int t, byte *rgba)
{
    const dword *cc;
    dword kk;

    cc = (const dword *)code;
    if (t & 16) {
    cc++;
    t &= 15;
    }
    t = (cc[0] >> (t * 2)) & 3;

    t *= 15;
    cc = (const dword *)(code + 8 + t / 8);
    kk = cc[0] >> (t & 7);
    rgba[BCOMP] = UP5(kk);
    rgba[GCOMP] = UP5(kk >> 5);
    rgba[RCOMP] = UP5(kk >> 10);
    rgba[ACOMP] = 255;
}


static void
fxt1_decode_1MIXED (const byte *code, int t, byte *rgba)
{
    const dword *cc;
    int col[2][3];
    int glsb, selb;

    cc = (const dword *)code;
    if (t & 16) {
    t &= 15;
    t = (cc[1] >> (t * 2)) & 3;
    /* col 2 */
    col[0][BCOMP] = (*(const dword *)(code + 11)) >> 6;
    col[0][GCOMP] = CC_SEL(cc, 99);
    col[0][RCOMP] = CC_SEL(cc, 104);
    /* col 3 */
    col[1][BCOMP] = CC_SEL(cc, 109);
    col[1][GCOMP] = CC_SEL(cc, 114);
    col[1][RCOMP] = CC_SEL(cc, 119);
    glsb = CC_SEL(cc, 126);
    selb = CC_SEL(cc, 33);
    } else {
    t = (cc[0] >> (t * 2)) & 3;
    /* col 0 */
    col[0][BCOMP] = CC_SEL(cc, 64);
    col[0][GCOMP] = CC_SEL(cc, 69);
    col[0][RCOMP] = CC_SEL(cc, 74);
    /* col 1 */
    col[1][BCOMP] = CC_SEL(cc, 79);
    col[1][GCOMP] = CC_SEL(cc, 84);
    col[1][RCOMP] = CC_SEL(cc, 89);
    glsb = CC_SEL(cc, 125);
    selb = CC_SEL(cc, 1);
    }

    if (CC_SEL(cc, 124) & 1) {
    /* alpha[0] == 1 */

    if (t == 3) {
        ZERO_4UBV(rgba);
    } else {
        if (t == 0) {
        rgba[BCOMP] = UP5(col[0][BCOMP]);
        rgba[GCOMP] = UP5(col[0][GCOMP]);
        rgba[RCOMP] = UP5(col[0][RCOMP]);
        } else if (t == 2) {
        rgba[BCOMP] = UP5(col[1][BCOMP]);
        rgba[GCOMP] = UP6(col[1][GCOMP], glsb);
        rgba[RCOMP] = UP5(col[1][RCOMP]);
        } else {
        rgba[BCOMP] = (UP5(col[0][BCOMP]) + UP5(col[1][BCOMP])) / 2;
        rgba[GCOMP] = (UP5(col[0][GCOMP]) + UP6(col[1][GCOMP], glsb)) / 2;
        rgba[RCOMP] = (UP5(col[0][RCOMP]) + UP5(col[1][RCOMP])) / 2;
        }
        rgba[ACOMP] = 255;
    }
    } else {
    /* alpha[0] == 0 */

    if (t == 0) {
        rgba[BCOMP] = UP5(col[0][BCOMP]);
        rgba[GCOMP] = UP6(col[0][GCOMP], glsb ^ selb);
        rgba[RCOMP] = UP5(col[0][RCOMP]);
    } else if (t == 3) {
        rgba[BCOMP] = UP5(col[1][BCOMP]);
        rgba[GCOMP] = UP6(col[1][GCOMP], glsb);
        rgba[RCOMP] = UP5(col[1][RCOMP]);
    } else {
        rgba[BCOMP] = LERP(3, t, UP5(col[0][BCOMP]), UP5(col[1][BCOMP]));
        rgba[GCOMP] = LERP(3, t, UP6(col[0][GCOMP], glsb ^ selb),
                     UP6(col[1][GCOMP], glsb));
        rgba[RCOMP] = LERP(3, t, UP5(col[0][RCOMP]), UP5(col[1][RCOMP]));
    }
    rgba[ACOMP] = 255;
    }
}


static void
fxt1_decode_1ALPHA (const byte *code, int t, byte *rgba)
{
    const dword *cc;

    cc = (const dword *)code;
    if (CC_SEL(cc, 124) & 1) {
    /* lerp == 1 */
    int col0[4];

    if (t & 16) {
        t &= 15;
        t = (cc[1] >> (t * 2)) & 3;
        /* col 2 */
        col0[BCOMP] = (*(const dword *)(code + 11)) >> 6;
        col0[GCOMP] = CC_SEL(cc, 99);
        col0[RCOMP] = CC_SEL(cc, 104);
        col0[ACOMP] = CC_SEL(cc, 119);
    } else {
        t = (cc[0] >> (t * 2)) & 3;
        /* col 0 */
        col0[BCOMP] = CC_SEL(cc, 64);
        col0[GCOMP] = CC_SEL(cc, 69);
        col0[RCOMP] = CC_SEL(cc, 74);
        col0[ACOMP] = CC_SEL(cc, 109);
    }

    if (t == 0) {
        rgba[BCOMP] = UP5(col0[BCOMP]);
        rgba[GCOMP] = UP5(col0[GCOMP]);
        rgba[RCOMP] = UP5(col0[RCOMP]);
        rgba[ACOMP] = UP5(col0[ACOMP]);
    } else if (t == 3) {
        rgba[BCOMP] = UP5(CC_SEL(cc, 79));
        rgba[GCOMP] = UP5(CC_SEL(cc, 84));
        rgba[RCOMP] = UP5(CC_SEL(cc, 89));
        rgba[ACOMP] = UP5(CC_SEL(cc, 114));
    } else {
        rgba[BCOMP] = LERP(3, t, UP5(col0[BCOMP]), UP5(CC_SEL(cc, 79)));
        rgba[GCOMP] = LERP(3, t, UP5(col0[GCOMP]), UP5(CC_SEL(cc, 84)));
        rgba[RCOMP] = LERP(3, t, UP5(col0[RCOMP]), UP5(CC_SEL(cc, 89)));
        rgba[ACOMP] = LERP(3, t, UP5(col0[ACOMP]), UP5(CC_SEL(cc, 114)));
    }
    } else {
    /* lerp == 0 */

    if (t & 16) {
        cc++;
        t &= 15;
    }
    t = (cc[0] >> (t * 2)) & 3;

    if (t == 3) {
        ZERO_4UBV(rgba);
    } else {
        dword kk;
        cc = (const dword *)code;
        rgba[ACOMP] = UP5(cc[3] >> (t * 5 + 13));
        t *= 15;
        cc = (const dword *)(code + 8 + t / 8);
        kk = cc[0] >> (t & 7);
        rgba[BCOMP] = UP5(kk);
        rgba[GCOMP] = UP5(kk >> 5);
        rgba[RCOMP] = UP5(kk >> 10);
    }
    }
}


TAPI void TAPIENTRY
fxt1_decode_1 (const void *texture, int stride,
           int i, int j, byte *rgba)
{
    static void (*decode_1[]) (const byte *, int, byte *) = {
    fxt1_decode_1HI,    /* cc-high   = "00?" */
    fxt1_decode_1HI,    /* cc-high   = "00?" */
    fxt1_decode_1CHROMA,    /* cc-chroma = "010" */
    fxt1_decode_1ALPHA, /* alpha     = "011" */
    fxt1_decode_1MIXED, /* mixed     = "1??" */
    fxt1_decode_1MIXED, /* mixed     = "1??" */
    fxt1_decode_1MIXED, /* mixed     = "1??" */
    fxt1_decode_1MIXED  /* mixed     = "1??" */
    };

    const byte *code = (const byte *)texture +
            ((j / 4) * (stride / 8) + (i / 8)) * 16;
    int mode = CC_SEL(code, 125);
    int t = i & 7;

    if (t & 4) {
    t += 12;
    }
    t += (j & 3) * 4;

    decode_1[mode](code, t, rgba);

#if VERBOSE
    {
    extern int cc_chroma;
    extern int cc_alpha;
    extern int cc_high;
    extern int cc_mixed;
    static int *cctype[] = {
        &cc_high,
        &cc_high,
        &cc_chroma,
        &cc_alpha,
        &cc_mixed,
        &cc_mixed,
        &cc_mixed,
        &cc_mixed
    };
    (*cctype[mode])++;
    }
#endif
}