/*tex

    I reformatted the file a bit and also assume a modern C compiler so we don't need some 
    macros. We also plug into the memory allocators that we use. So, some code has been 
    removed. The original code is in |nanojpeg-original.c| and has some more comments. I 
    took the code from: 

        https://keyj.emphy.de/nanojpeg/

    I will probably reformat the code a bit when I look more closely. Performance is quite 
    okay for our purpose. If needed we can look into speeding up. I'll also look into more 
    recent C approaches like local ints in loops and so. 

    HH 

*/

/* 

    NanoJPEG -- KeyJ's Tiny Baseline JPEG Decoder
    version 1.3.5 (2016-11-14)
    Copyright (c) 2009-2016 Martin J. Fiedler <martin.fiedler@gmx.net>
    published under the terms of the MIT license
    
    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 THE
    AUTHORS OR COPYRIGHT HOLDERS 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.

*/

/* 
    INTRODUCTION

    This is a minimal decoder for baseline JPEG images. It accepts memory dumps
    of JPEG files as input and generates either 8-bit grayscale or packed 24-bit
    RGB images as output. It does not parse JFIF or Exif headers; all JPEG files
    are assumed to be either grayscale or YCbCr. CMYK or other color spaces are
    not supported. All YCbCr subsampling schemes with power-of-two ratios are
    supported, as are restart intervals. Progressive or lossless JPEG is not
    supported.

    Summed up, NanoJPEG should be able to decode all images from digital cameras
    and most common forms of other non-progressive JPEG images.
    The decoder is not optimized for speed, it's optimized for simplicity and
    small code. Image quality should be at a reasonable level. A bicubic chroma
    upsampling filter ensures that subsampled YCbCr images are rendered in
    decent quality. The decoder is not meant to deal with broken JPEG files in
    a graceful manner; if anything is wrong with the bitstream, decoding will
    simply fail.

*/
# include "nanojpeg.h"
# include "utilities/auxmemory.h"

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

# define njAllocMem lmt_memory_malloc
# define njFreeMem  lmt_memory_free

# define njFillMem  memset
# define njCopyMem  memcpy

typedef struct _nj_code {
    unsigned char bits, code;
} nj_vlc_code_t;

typedef struct _nj_cmp {
    int cid;
    int ssx, ssy;
    int width, height;
    int stride;
    int qtsel;
    int actabsel, dctabsel;
    int dcpred;
    unsigned char *pixels;
} nj_component_t;

typedef struct _nj_ctx {
    nj_result_t error;
    const unsigned char *pos;
    int size;
    int length;
    int width, height;
    int mbwidth, mbheight;
    int mbsizex, mbsizey;
    int ncomp;
    nj_component_t comp[3];
    int qtused, qtavail;
    unsigned char qtab[4][64];
    nj_vlc_code_t vlctab[4][65536];
    int buf, bufbits;
    int block[64];
    int rstinterval;
    unsigned char *rgb;
} nj_context_t;

static nj_context_t nj;

static const char njZZ[64] = { 
    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 
};

static inline unsigned char njClip(const int x) 
{
    return (x < 0) ? 0 : ((x > 0xFF) ? 0xFF : (unsigned char) x);
}

# define W1 2841
# define W2 2676
# define W3 2408
# define W5 1609
# define W6 1108
# define W7  565

static inline void njRowIDCT(int* blk) 
{
    int x0, x1, x2, x3, x4, x5, x6, x7, x8;
    if (!((x1 = blk[4] << 11)
        | (x2 = blk[6])
        | (x3 = blk[2])
        | (x4 = blk[1])
        | (x5 = blk[7])
        | (x6 = blk[5])
        | (x7 = blk[3])))
    {
        blk[0] = blk[1] = blk[2] = blk[3] = blk[4] = blk[5] = blk[6] = blk[7] = blk[0] << 3;
        return;
    }
    x0 = (blk[0] << 11) + 128;
    x8 = W7 * (x4 + x5);
    x4 = x8 + (W1 - W7) * x4;
    x5 = x8 - (W1 + W7) * x5;
    x8 = W3 * (x6 + x7);
    x6 = x8 - (W3 - W5) * x6;
    x7 = x8 - (W3 + W5) * x7;
    x8 = x0 + x1;
    x0 -= x1;
    x1 = W6 * (x3 + x2);
    x2 = x1 - (W2 + W6) * x2;
    x3 = x1 + (W2 - W6) * x3;
    x1 = x4 + x6;
    x4 -= x6;
    x6 = x5 + x7;
    x5 -= x7;
    x7 = x8 + x3;
    x8 -= x3;
    x3 = x0 + x2;
    x0 -= x2;
    x2 = (181 * (x4 + x5) + 128) >> 8;
    x4 = (181 * (x4 - x5) + 128) >> 8;
    blk[0] = (x7 + x1) >> 8;
    blk[1] = (x3 + x2) >> 8;
    blk[2] = (x0 + x4) >> 8;
    blk[3] = (x8 + x6) >> 8;
    blk[4] = (x8 - x6) >> 8;
    blk[5] = (x0 - x4) >> 8;
    blk[6] = (x3 - x2) >> 8;
    blk[7] = (x7 - x1) >> 8;
}

static inline void njColIDCT(const int* blk, unsigned char *out, int stride) 
{
    int x0, x1, x2, x3, x4, x5, x6, x7, x8;
    if (!((x1 = blk[8*4] << 8)
        | (x2 = blk[8*6])
        | (x3 = blk[8*2])
        | (x4 = blk[8*1])
        | (x5 = blk[8*7])
        | (x6 = blk[8*5])
        | (x7 = blk[8*3])))
    {
        x1 = njClip(((blk[0] + 32) >> 6) + 128);
        for (x0 = 8;  x0;  --x0) {
            *out = (unsigned char) x1;
            out += stride;
        }
        return;
    }
    x0 = (blk[0] << 8) + 8192;
    x8 = W7 * (x4 + x5) + 4;
    x4 = (x8 + (W1 - W7) * x4) >> 3;
    x5 = (x8 - (W1 + W7) * x5) >> 3;
    x8 = W3 * (x6 + x7) + 4;
    x6 = (x8 - (W3 - W5) * x6) >> 3;
    x7 = (x8 - (W3 + W5) * x7) >> 3;
    x8 = x0 + x1;
    x0 -= x1;
    x1 = W6 * (x3 + x2) + 4;
    x2 = (x1 - (W2 + W6) * x2) >> 3;
    x3 = (x1 + (W2 - W6) * x3) >> 3;
    x1 = x4 + x6;
    x4 -= x6;
    x6 = x5 + x7;
    x5 -= x7;
    x7 = x8 + x3;
    x8 -= x3;
    x3 = x0 + x2;
    x0 -= x2;
    x2 = (181 * (x4 + x5) + 128) >> 8;
    x4 = (181 * (x4 - x5) + 128) >> 8;
    *out = njClip(((x7 + x1) >> 14) + 128);  out += stride;
    *out = njClip(((x3 + x2) >> 14) + 128);  out += stride;
    *out = njClip(((x0 + x4) >> 14) + 128);  out += stride;
    *out = njClip(((x8 + x6) >> 14) + 128);  out += stride;
    *out = njClip(((x8 - x6) >> 14) + 128);  out += stride;
    *out = njClip(((x0 - x4) >> 14) + 128);  out += stride;
    *out = njClip(((x3 - x2) >> 14) + 128);  out += stride;
    *out = njClip(((x7 - x1) >> 14) + 128);
}

# define njThrow(e)     do { nj.error = e; return; } while (0)
# define njCheckError() do { if (nj.error) return; } while (0)

static int njShowBits(int bits) 
{
    unsigned char newbyte;
    if (!bits) return 0;
    while (nj.bufbits < bits) {
        if (nj.size <= 0) {
            nj.buf = (nj.buf << 8) | 0xFF;
            nj.bufbits += 8;
            continue;
        }
        newbyte = *nj.pos++;
        nj.size--;
        nj.bufbits += 8;
        nj.buf = (nj.buf << 8) | newbyte;
        if (newbyte == 0xFF) {
            if (nj.size) {
                unsigned char marker = *nj.pos++;
                nj.size--;
                switch (marker) {
                    case 0x00:
                    case 0xFF:
                        break;
                    case 0xD9: 
                        nj.size = 0; 
                        break;
                    default:
                        if ((marker & 0xF8) != 0xD0) {
                            nj.error = NJ_SYNTAX_ERROR;
                        } else {
                            nj.buf = (nj.buf << 8) | marker;
                            nj.bufbits += 8;
                        }
                }
            } else {
                nj.error = NJ_SYNTAX_ERROR;
            }
        }
    }
    return (nj.buf >> (nj.bufbits - bits)) & ((1 << bits) - 1);
}

static inline void njSkipBits(int bits) 
{
    if (nj.bufbits < bits)
        (void) njShowBits(bits);
    nj.bufbits -= bits;
}

static inline int njGetBits(int bits) 
{
    int res = njShowBits(bits);
    njSkipBits(bits);
    return res;
}

static inline void njByteAlign(void) 
{
    nj.bufbits &= 0xF8;
}

static inline void njSkip(int count) 
{
    nj.pos += count;
    nj.size -= count;
    nj.length -= count;
    if (nj.size < 0) nj.error = NJ_SYNTAX_ERROR;
}

static inline unsigned short njDecode16(const unsigned char *pos) 
{
    return (pos[0] << 8) | pos[1];
}

static inline void njDecodeLength(void) 
{
    if (nj.size < 2) njThrow(NJ_SYNTAX_ERROR);
    nj.length = njDecode16(nj.pos);
    if (nj.length > nj.size) njThrow(NJ_SYNTAX_ERROR);
    njSkip(2);
}

static inline void njSkipMarker(void) 
{
    njDecodeLength();
    njSkip(nj.length);
}

static inline void njDecodeSOF(void) 
{
    int i, ssxmax = 0, ssymax = 0;
    nj_component_t* c;
    njDecodeLength();
    njCheckError();
    if (nj.length < 9) njThrow(NJ_SYNTAX_ERROR);
    if (nj.pos[0] != 8) njThrow(NJ_UNSUPPORTED);
    nj.height = njDecode16(nj.pos+1);
    nj.width = njDecode16(nj.pos+3);
    if (!nj.width || !nj.height) njThrow(NJ_SYNTAX_ERROR);
    nj.ncomp = nj.pos[5];
    njSkip(6);
    switch (nj.ncomp) {
        case 1:
        case 3:
            break;
        default:
            njThrow(NJ_UNSUPPORTED);
    }
    if (nj.length < (nj.ncomp * 3)) njThrow(NJ_SYNTAX_ERROR);
    for (i = 0, c = nj.comp;  i < nj.ncomp;  ++i, ++c) {
        c->cid = nj.pos[0];
        if (!(c->ssx = nj.pos[1] >> 4)) njThrow(NJ_SYNTAX_ERROR);
        if (c->ssx & (c->ssx - 1)) njThrow(NJ_UNSUPPORTED);  // non-power of two
        if (!(c->ssy = nj.pos[1] & 15)) njThrow(NJ_SYNTAX_ERROR);
        if (c->ssy & (c->ssy - 1)) njThrow(NJ_UNSUPPORTED);  // non-power of two
        if ((c->qtsel = nj.pos[2]) & 0xFC) njThrow(NJ_SYNTAX_ERROR);
        njSkip(3);
        nj.qtused |= 1 << c->qtsel;
        if (c->ssx > ssxmax) ssxmax = c->ssx;
        if (c->ssy > ssymax) ssymax = c->ssy;
    }
    if (nj.ncomp == 1) {
        c = nj.comp;
        c->ssx = c->ssy = ssxmax = ssymax = 1;
    }
    nj.mbsizex = ssxmax << 3;
    nj.mbsizey = ssymax << 3;
    nj.mbwidth = (nj.width + nj.mbsizex - 1) / nj.mbsizex;
    nj.mbheight = (nj.height + nj.mbsizey - 1) / nj.mbsizey;
    for (i = 0, c = nj.comp;  i < nj.ncomp;  ++i, ++c) {
        c->width = (nj.width * c->ssx + ssxmax - 1) / ssxmax;
        c->height = (nj.height * c->ssy + ssymax - 1) / ssymax;
        c->stride = nj.mbwidth * c->ssx << 3;
        if (((c->width < 3) && (c->ssx != ssxmax)) || ((c->height < 3) && (c->ssy != ssymax))) njThrow(NJ_UNSUPPORTED);
        if (!(c->pixels = (unsigned char*) njAllocMem(c->stride * nj.mbheight * c->ssy << 3))) njThrow(NJ_OUT_OF_MEM);
    }
    if (nj.ncomp == 3) {
        nj.rgb = (unsigned char*) njAllocMem(nj.width * nj.height * nj.ncomp);
        if (!nj.rgb) njThrow(NJ_OUT_OF_MEM);
    }
    njSkip(nj.length);
}

static inline void njDecodeDHT(void) 
{
    int codelen, currcnt, remain, spread, i, j;
    nj_vlc_code_t *vlc;
    static unsigned char counts[16];
    njDecodeLength();
    njCheckError();
    while (nj.length >= 17) {
        i = nj.pos[0];
        if (i & 0xEC) njThrow(NJ_SYNTAX_ERROR);
        if (i & 0x02) njThrow(NJ_UNSUPPORTED);
        i = (i | (i >> 3)) & 3;  // combined DC/AC + tableid value
        for (codelen = 1;  codelen <= 16;  ++codelen)
            counts[codelen - 1] = nj.pos[codelen];
        njSkip(17);
        vlc = &nj.vlctab[i][0];
        remain = spread = 65536;
        for (codelen = 1;  codelen <= 16;  ++codelen) {
            spread >>= 1;
            currcnt = counts[codelen - 1];
            if (!currcnt) continue;
            if (nj.length < currcnt) njThrow(NJ_SYNTAX_ERROR);
            remain -= currcnt << (16 - codelen);
            if (remain < 0) njThrow(NJ_SYNTAX_ERROR);
            for (i = 0;  i < currcnt;  ++i) {
                register unsigned char code = nj.pos[i];
                for (j = spread;  j;  --j) {
                    vlc->bits = (unsigned char) codelen;
                    vlc->code = code;
                    ++vlc;
                }
            }
            njSkip(currcnt);
        }
        while (remain--) {
            vlc->bits = 0;
            ++vlc;
        }
    }
    if (nj.length) njThrow(NJ_SYNTAX_ERROR);
}

static inline void njDecodeDQT(void) 
{
    int i;
    unsigned char *t;
    njDecodeLength();
    njCheckError();
    while (nj.length >= 65) {
        i = nj.pos[0];
        if (i & 0xFC) njThrow(NJ_SYNTAX_ERROR);
        nj.qtavail |= 1 << i;
        t = &nj.qtab[i][0];
        for (i = 0;  i < 64;  ++i)
            t[i] = nj.pos[i + 1];
        njSkip(65);
    }
    if (nj.length) njThrow(NJ_SYNTAX_ERROR);
}

static inline void njDecodeDRI(void) 
{
    njDecodeLength();
    njCheckError();
    if (nj.length < 2) njThrow(NJ_SYNTAX_ERROR);
    nj.rstinterval = njDecode16(nj.pos);
    njSkip(nj.length);
}

static inline int njGetVLC(nj_vlc_code_t* vlc, unsigned char* code) 
{
    int value = njShowBits(16);
    int bits = vlc[value].bits;
    if (!bits) { nj.error = NJ_SYNTAX_ERROR; return 0; }
    njSkipBits(bits);
    value = vlc[value].code;
    if (code) *code = (unsigned char) value;
    bits = value & 15;
    if (!bits) return 0;
    value = njGetBits(bits);
    if (value < (1 << (bits - 1)))
        value += ((-1) << bits) + 1;
    return value;
}

static inline void njDecodeBlock(nj_component_t* c, unsigned char* out) 
{
    unsigned char code = 0;
    int value, coef = 0;
    njFillMem(nj.block, 0, sizeof(nj.block));
    c->dcpred += njGetVLC(&nj.vlctab[c->dctabsel][0], NULL);
    nj.block[0] = (c->dcpred) * nj.qtab[c->qtsel][0];
    do {
        value = njGetVLC(&nj.vlctab[c->actabsel][0], &code);
        if (!code) break;  // EOB
        if (!(code & 0x0F) && (code != 0xF0)) njThrow(NJ_SYNTAX_ERROR);
        coef += (code >> 4) + 1;
        if (coef > 63) njThrow(NJ_SYNTAX_ERROR);
        nj.block[(int) njZZ[coef]] = value * nj.qtab[c->qtsel][coef];
    } while (coef < 63);
    for (coef = 0;  coef < 64;  coef += 8)
        njRowIDCT(&nj.block[coef]);
    for (coef = 0;  coef < 8;  ++coef)
        njColIDCT(&nj.block[coef], &out[coef], c->stride);
}

static inline void njDecodeScan(void) 
{
    int i, mbx, mby, sbx, sby;
    int rstcount = nj.rstinterval, nextrst = 0;
    nj_component_t* c;
    njDecodeLength();
    njCheckError();
    if (nj.length < (4 + 2 * nj.ncomp)) njThrow(NJ_SYNTAX_ERROR);
    if (nj.pos[0] != nj.ncomp) njThrow(NJ_UNSUPPORTED);
    njSkip(1);
    for (i = 0, c = nj.comp;  i < nj.ncomp;  ++i, ++c) {
        if (nj.pos[0] != c->cid) njThrow(NJ_SYNTAX_ERROR);
        if (nj.pos[1] & 0xEE) njThrow(NJ_SYNTAX_ERROR);
        c->dctabsel = nj.pos[1] >> 4;
        c->actabsel = (nj.pos[1] & 1) | 2;
        njSkip(2);
    }
    if (nj.pos[0] || (nj.pos[1] != 63) || nj.pos[2]) njThrow(NJ_UNSUPPORTED);
    njSkip(nj.length);
    for (mbx = mby = 0;;) {
        for (i = 0, c = nj.comp;  i < nj.ncomp;  ++i, ++c)
            for (sby = 0;  sby < c->ssy;  ++sby)
                for (sbx = 0;  sbx < c->ssx;  ++sbx) {
                    njDecodeBlock(c, &c->pixels[((mby * c->ssy + sby) * c->stride + mbx * c->ssx + sbx) << 3]);
                    njCheckError();
                }
        if (++mbx >= nj.mbwidth) {
            mbx = 0;
            if (++mby >= nj.mbheight) break;
        }
        if (nj.rstinterval && !(--rstcount)) {
            njByteAlign();
            i = njGetBits(16);
            if (((i & 0xFFF8) != 0xFFD0) || ((i & 7) != nextrst)) njThrow(NJ_SYNTAX_ERROR);
            nextrst = (nextrst + 1) & 7;
            rstcount = nj.rstinterval;
            for (i = 0;  i < 3;  ++i)
                nj.comp[i].dcpred = 0;
        }
    }
    nj.error = __NJ_FINISHED;
}

# define CF4A  (-9)
# define CF4B (111)
# define CF4C  (29)
# define CF4D  (-3)
# define CF3A  (28)
# define CF3B (109)
# define CF3C  (-9)
# define CF3X (104)
# define CF3Y  (27)
# define CF3Z  (-3)
# define CF2A (139)
# define CF2B (-11)
# define CF(x) njClip(((x) + 64) >> 7)

static inline void njUpsampleH(nj_component_t* c) 
{
    const int xmax = c->width - 3;
    unsigned char *out, *lin, *lout;
    int x, y;
    out = (unsigned char*) njAllocMem((c->width * c->height) << 1);
    if (!out) njThrow(NJ_OUT_OF_MEM);
    lin = c->pixels;
    lout = out;
    for (y = c->height;  y;  --y) {
        lout[0] = CF(CF2A * lin[0] + CF2B * lin[1]);
        lout[1] = CF(CF3X * lin[0] + CF3Y * lin[1] + CF3Z * lin[2]);
        lout[2] = CF(CF3A * lin[0] + CF3B * lin[1] + CF3C * lin[2]);
        for (x = 0;  x < xmax;  ++x) {
            lout[(x << 1) + 3] = CF(CF4A * lin[x] + CF4B * lin[x + 1] + CF4C * lin[x + 2] + CF4D * lin[x + 3]);
            lout[(x << 1) + 4] = CF(CF4D * lin[x] + CF4C * lin[x + 1] + CF4B * lin[x + 2] + CF4A * lin[x + 3]);
        }
        lin += c->stride;
        lout += c->width << 1;
        lout[-3] = CF(CF3A * lin[-1] + CF3B * lin[-2] + CF3C * lin[-3]);
        lout[-2] = CF(CF3X * lin[-1] + CF3Y * lin[-2] + CF3Z * lin[-3]);
        lout[-1] = CF(CF2A * lin[-1] + CF2B * lin[-2]);
    }
    c->width <<= 1;
    c->stride = c->width;
    njFreeMem((void*)c->pixels);
    c->pixels = out;
}

static inline void njUpsampleV(nj_component_t* c) 
{
    const int w = c->width, s1 = c->stride, s2 = s1 + s1;
    unsigned char *out, *cin, *cout;
    int x, y;
    out = (unsigned char*) njAllocMem((c->width * c->height) << 1);
    if (!out) njThrow(NJ_OUT_OF_MEM);
    for (x = 0;  x < w;  ++x) {
        cin = &c->pixels[x];
        cout = &out[x];
        *cout = CF(CF2A * cin[0] + CF2B * cin[s1]);  cout += w;
        *cout = CF(CF3X * cin[0] + CF3Y * cin[s1] + CF3Z * cin[s2]);  cout += w;
        *cout = CF(CF3A * cin[0] + CF3B * cin[s1] + CF3C * cin[s2]);  cout += w;
        cin += s1;
        for (y = c->height - 3;  y;  --y) {
            *cout = CF(CF4A * cin[-s1] + CF4B * cin[0] + CF4C * cin[s1] + CF4D * cin[s2]);  cout += w;
            *cout = CF(CF4D * cin[-s1] + CF4C * cin[0] + CF4B * cin[s1] + CF4A * cin[s2]);  cout += w;
            cin += s1;
        }
        cin += s1;
        *cout = CF(CF3A * cin[0] + CF3B * cin[-s1] + CF3C * cin[-s2]);  cout += w;
        *cout = CF(CF3X * cin[0] + CF3Y * cin[-s1] + CF3Z * cin[-s2]);  cout += w;
        *cout = CF(CF2A * cin[0] + CF2B * cin[-s1]);
    }
    c->height <<= 1;
    c->stride = c->width;
    njFreeMem((void*) c->pixels);
    c->pixels = out;
}

static inline void njConvert(void) 
{
    int i;
    nj_component_t* c;
    for (i = 0, c = nj.comp;  i < nj.ncomp;  ++i, ++c) {
        while ((c->width < nj.width) || (c->height < nj.height)) {
            if (c->width < nj.width) njUpsampleH(c);
            njCheckError();
            if (c->height < nj.height) njUpsampleV(c);
            njCheckError();
        }
        if ((c->width < nj.width) || (c->height < nj.height)) njThrow(NJ_INTERNAL_ERR);
    }
    if (nj.ncomp == 3) {
        // convert to RGB
        int x, yy;
        unsigned char *prgb = nj.rgb;
        const unsigned char *py  = nj.comp[0].pixels;
        const unsigned char *pcb = nj.comp[1].pixels;
        const unsigned char *pcr = nj.comp[2].pixels;
        for (yy = nj.height;  yy;  --yy) {
            for (x = 0;  x < nj.width;  ++x) {
                register int y = py[x] << 8;
                register int cb = pcb[x] - 128;
                register int cr = pcr[x] - 128;
                *prgb++ = njClip((y            + 359 * cr + 128) >> 8);
                *prgb++ = njClip((y -  88 * cb - 183 * cr + 128) >> 8);
                *prgb++ = njClip((y + 454 * cb            + 128) >> 8);
            }
            py += nj.comp[0].stride;
            pcb += nj.comp[1].stride;
            pcr += nj.comp[2].stride;
        }
    } else if (nj.comp[0].width != nj.comp[0].stride) {
        // grayscale -> only remove stride
        unsigned char *pin = &nj.comp[0].pixels[nj.comp[0].stride];
        unsigned char *pout = &nj.comp[0].pixels[nj.comp[0].width];
        int y;
        for (y = nj.comp[0].height - 1;  y;  --y) {
            njCopyMem(pout, pin, nj.comp[0].width);
            pin += nj.comp[0].stride;
            pout += nj.comp[0].width;
        }
        nj.comp[0].stride = nj.comp[0].width;
    }
}

void njInit(void) 
{
    njFillMem(&nj, 0, sizeof(nj_context_t));
}

void njDone(void) 
{
    int i;
    for (i = 0;  i < 3;  ++i)
        if (nj.comp[i].pixels) njFreeMem((void*) nj.comp[i].pixels);
    if (nj.rgb) njFreeMem((void*) nj.rgb);
    njInit();
}

nj_result_t njDecode(const void* jpeg, const int size) 
{
    njDone();
    nj.pos = (const unsigned char*) jpeg;
    nj.size = size & 0x7FFFFFFF;
    if (nj.size < 2) return NJ_NO_JPEG;
    if ((nj.pos[0] ^ 0xFF) | (nj.pos[1] ^ 0xD8)) return NJ_NO_JPEG;
    njSkip(2);
    while (!nj.error) {
        if ((nj.size < 2) || (nj.pos[0] != 0xFF)) return NJ_SYNTAX_ERROR;
        njSkip(2);
        switch (nj.pos[-1]) {
            case 0xC0: njDecodeSOF();  break;
            case 0xC4: njDecodeDHT();  break;
            case 0xDB: njDecodeDQT();  break;
            case 0xDD: njDecodeDRI();  break;
            case 0xDA: njDecodeScan(); break;
            case 0xFE: njSkipMarker(); break;
            default:
                if ((nj.pos[-1] & 0xF0) == 0xE0)
                    njSkipMarker();
                else
                    return NJ_UNSUPPORTED;
        }
    }
    if (nj.error != __NJ_FINISHED) return nj.error;
    nj.error = NJ_OK;
    njConvert();
    return nj.error;
}

int njGetWidth(void)
{ 
    return nj.width; 
}

int njGetHeight(void)
{ 
    return nj.height; 
}

int njIsColor(void)
{ 
    return (nj.ncomp != 1); 
}

unsigned char* njGetImage(void) { 
    return (nj.ncomp == 1) ? nj.comp[0].pixels : nj.rgb; 
}

int njGetImageSize(void)       
{ 
    return nj.width * nj.height * nj.ncomp; 
}