ujpeg.cpp

// uJPEG (MicroJPEG) -- KeyJ's Small Baseline JPEG Decoder
// based on 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.
#include "pch.h"

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

#include "ujpeg.h"

/* UJ_NODECODE_BLOCK_SIZE: if #defined, this specifies the amount of bytes
 * to load from disk if ujDecodeFile() is used after ujDisableDecoding().
 * This will speed up checking of large files, because not the whole file has
 * to be read, but just a small portion of it. On the other hand, it will also
 * break checking of files where the actual image data starts after this point
 * (though it's questionable if any real-world file would ever trigger that). */
#define UJ_NODECODE_BLOCK_SIZE (256 * 1024)

#ifdef _MSC_VER
#define UJ_INLINE static __inline
#define UJ_FORCE_INLINE static __forceinline
#else
#define UJ_INLINE static inline
#define UJ_FORCE_INLINE static inline
#endif

#ifdef __cplusplus
extern "C" {
#endif

    typedef struct _uj_code {
        unsigned char bits, code;
    } ujVLCCode;

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

    typedef struct _uj_ctx {
        const unsigned char* pos;
        int valid, decoded;
        int no_decode;
        int fast_chroma;
        int size;
        int length;
        int width, height;
        int mbwidth, mbheight;
        int mbsizex, mbsizey;
        int ncomp;
        ujComponent comp[3];
        int qtused, qtavail;
        unsigned char qtab[4][64];
        ujVLCCode vlctab[8][65536];
        int buf, bufbits;
        int block[64];
        int rstinterval;
        unsigned char* rgb;
        int exif_le;
        int co_sited_chroma;
        bool mapx;  // 大话2旧地图特殊处理
    } ujContext;

    static ujResult ujError = UJ_OK;

    static const char ujZZ[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 };

    UJ_FORCE_INLINE unsigned char ujClip(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

    UJ_INLINE void ujRowIDCT(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;
    }

    UJ_INLINE void ujColIDCT(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 = ujClip(((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 = ujClip(((x7 + x1) >> 14) + 128);  out += stride;
        *out = ujClip(((x3 + x2) >> 14) + 128);  out += stride;
        *out = ujClip(((x0 + x4) >> 14) + 128);  out += stride;
        *out = ujClip(((x8 + x6) >> 14) + 128);  out += stride;
        *out = ujClip(((x8 - x6) >> 14) + 128);  out += stride;
        *out = ujClip(((x0 - x4) >> 14) + 128);  out += stride;
        *out = ujClip(((x3 - x2) >> 14) + 128);  out += stride;
        *out = ujClip(((x7 - x1) >> 14) + 128);
    }

    ///////////////////////////////////////////////////////////////////////////////

#define ujThrow(e) do { ujError = e; return; } while (0)
#define ujCheckError() do { if (ujError) return; } while (0)

    static int ujShowBits(ujContext* uj, int bits) {
        unsigned char newbyte;
        if (!bits) return 0;
        while (uj->bufbits < bits) {
            if (uj->size <= 0) {
                uj->buf = (uj->buf << 8) | 0xFF;
                uj->bufbits += 8;
                continue;
            }
            newbyte = *uj->pos++;
            uj->size--;
            uj->bufbits += 8;
            uj->buf = (uj->buf << 8) | newbyte;
            if (!uj->mapx && newbyte == 0xFF) {  // 大话2旧地图特殊处理   旧地图没有FF00
                if (uj->size) {
                    unsigned char marker = *uj->pos++;
                    uj->size--;
                    switch (marker) {
                    case 0x00:
                        // case 0xFF:
                        break;
                        // case 0xD9: 
                        //    uj->size = 0; break;
                    default:
                        // if ((marker & 0xF8) != 0xD0) {
                        //    ujError = UJ_SYNTAX_ERROR;
                        // } else {
                        //     uj->buf = (uj->buf << 8) | marker;
                        //     uj->bufbits += 8;
                        // }
                        uj->buf = (uj->buf << 8) | marker;
                        uj->bufbits += 8;
                    }
                }
                else
                    ujError = UJ_SYNTAX_ERROR;
            }
        }
        return (uj->buf >> (uj->bufbits - bits)) & ((1 << bits) - 1);
    }

    UJ_INLINE void ujSkipBits(ujContext* uj, int bits) {
        if (uj->bufbits < bits)
            (void)ujShowBits(uj, bits);
        uj->bufbits -= bits;
    }

    UJ_INLINE int ujGetBits(ujContext* uj, int bits) {
        int res = ujShowBits(uj, bits);
        ujSkipBits(uj, bits);
        return res;
    }

    UJ_INLINE void ujByteAlign(ujContext* uj) {
        uj->bufbits &= 0xF8;
    }

    static void ujSkip(ujContext* uj, int count) {
        uj->pos += count;
        uj->size -= count;
        uj->length -= count;
        if (uj->size < 0) ujError = UJ_SYNTAX_ERROR;
    }

    UJ_INLINE unsigned short ujDecode16(const unsigned char* pos) {
        return (pos[0] << 8) | pos[1];
    }

    UJ_INLINE unsigned short ujDecode16Reverse(const unsigned char* pos) {
        return (pos[1] << 8) | pos[0];
    }

    static void ujDecodeLength(ujContext* uj) {
        if (uj->size < 2) ujThrow(UJ_SYNTAX_ERROR);
        uj->length = ujDecode16(uj->pos);
        if (uj->length > uj->size) ujThrow(UJ_SYNTAX_ERROR);
        ujSkip(uj, 2);
    }

    UJ_INLINE void ujSkipMarker(ujContext* uj) {
        ujDecodeLength(uj);
        ujSkip(uj, uj->length);
    }

    UJ_INLINE void ujDecodeSOF(ujContext* uj) {
        int i, ssxmax = 0, ssymax = 0, size;
        ujComponent* c;
        ujDecodeLength(uj);
        ujCheckError();
        if (uj->length < 9) ujThrow(UJ_SYNTAX_ERROR);
        if (uj->pos[0] != 8) ujThrow(UJ_UNSUPPORTED);
        uj->height = ujDecode16(uj->pos + 1);
        uj->width = ujDecode16(uj->pos + 3);
        // 大话2旧地图特殊处理
        if (uj->mapx) {
            uj->height = 240;
            uj->width = 320;
        }
        if (!uj->width || !uj->height) ujThrow(UJ_SYNTAX_ERROR);
        uj->ncomp = uj->pos[5];
        ujSkip(uj, 6);
        switch (uj->ncomp) {
        case 1:
        case 3:
            break;
        default:
            ujThrow(UJ_UNSUPPORTED);
        }
        if (uj->length < (uj->ncomp * 3)) ujThrow(UJ_SYNTAX_ERROR);
        for (i = 0, c = uj->comp; i < uj->ncomp; ++i, ++c) {
            c->cid = uj->pos[0];
            if (!(c->ssx = uj->pos[1] >> 4)) ujThrow(UJ_SYNTAX_ERROR);
            if (c->ssx & (c->ssx - 1)) ujThrow(UJ_UNSUPPORTED);  // non-power of two
            if (!(c->ssy = uj->pos[1] & 15)) ujThrow(UJ_SYNTAX_ERROR);
            if (c->ssy & (c->ssy - 1)) ujThrow(UJ_UNSUPPORTED);  // non-power of two
            if ((c->qtsel = uj->pos[2]) & 0xFC) ujThrow(UJ_SYNTAX_ERROR);
            ujSkip(uj, 3);
            uj->qtused |= 1 << c->qtsel;
            if (c->ssx > ssxmax) ssxmax = c->ssx;
            if (c->ssy > ssymax) ssymax = c->ssy;
        }
        if (uj->ncomp == 1) {
            c = uj->comp;
            c->ssx = c->ssy = ssxmax = ssymax = 1;
        }
        uj->mbsizex = ssxmax << 3;
        uj->mbsizey = ssymax << 3;
        uj->mbwidth = (uj->width + uj->mbsizex - 1) / uj->mbsizex;
        uj->mbheight = (uj->height + uj->mbsizey - 1) / uj->mbsizey;
        for (i = 0, c = uj->comp; i < uj->ncomp; ++i, ++c) {
            c->width = (uj->width * c->ssx + ssxmax - 1) / ssxmax;
            c->height = (uj->height * c->ssy + ssymax - 1) / ssymax;
            c->stride = uj->mbwidth * c->ssx << 3;
            if (((c->width < 3) && (c->ssx != ssxmax)) || ((c->height < 3) && (c->ssy != ssymax))) ujThrow(UJ_UNSUPPORTED);
            if (!uj->no_decode) {
                size = c->stride * uj->mbheight * c->ssy << 3;
                if (!(c->pixels = (unsigned char*)malloc(size))) ujThrow(UJ_OUT_OF_MEM);
                memset(c->pixels, 0x80, size);
            }
        }
        ujSkip(uj, uj->length);
    }

    UJ_INLINE void ujDecodeDHT(ujContext* uj) {
        int codelen, currcnt, remain, spread, i, j;
        ujVLCCode* vlc;
        static unsigned char counts[16];
        ujDecodeLength(uj);
        ujCheckError();
        while (uj->length >= 17) {
            i = uj->pos[0];
            if (i & 0xEC) ujThrow(UJ_SYNTAX_ERROR);
            // 大话2新地图特殊处理
            // 
            // 取值现在为0~7
            // if (i & 0x02) ujThrow(UJ_UNSUPPORTED);
            i = (i | (i >> 2)) & 7;  // combined DC/AC + tableid value  
            // 0~3 为DC   4~7为AC
            for (codelen = 1; codelen <= 16; ++codelen)
                counts[codelen - 1] = uj->pos[codelen];
            ujSkip(uj, 17);
            vlc = &uj->vlctab[i][0];
            remain = spread = 65536;
            for (codelen = 1; codelen <= 16; ++codelen) {
                spread >>= 1;
                currcnt = counts[codelen - 1];
                if (!currcnt) continue;
                if (uj->length < currcnt) ujThrow(UJ_SYNTAX_ERROR);
                remain -= currcnt << (16 - codelen);
                if (remain < 0) ujThrow(UJ_SYNTAX_ERROR);
                for (i = 0; i < currcnt; ++i) {
                    register unsigned char code = uj->pos[i];
                    for (j = spread; j; --j) {
                        vlc->bits = (unsigned char)codelen;
                        vlc->code = code;
                        ++vlc;
                    }
                }
                ujSkip(uj, currcnt);
            }
            while (remain--) {
                vlc->bits = 0;
                ++vlc;
            }
        }
        if (uj->length) ujThrow(UJ_SYNTAX_ERROR);
    }

    UJ_INLINE void ujDecodeDQT(ujContext* uj) {
        int i;
        unsigned char* t;
        ujDecodeLength(uj);
        ujCheckError();
        while (uj->length >= 65) {
            i = uj->pos[0];
            if (i & 0xFC) ujThrow(UJ_SYNTAX_ERROR);
            uj->qtavail |= 1 << i;
            t = &uj->qtab[i][0];
            for (i = 0; i < 64; ++i)
                t[i] = uj->pos[i + 1];
            ujSkip(uj, 65);
        }
        if (uj->length) ujThrow(UJ_SYNTAX_ERROR);
    }

    UJ_INLINE void ujDecodeDRI(ujContext* uj) {
        ujDecodeLength(uj);
        ujCheckError();
        if (uj->length < 2) ujThrow(UJ_SYNTAX_ERROR);
        uj->rstinterval = ujDecode16(uj->pos);
        ujSkip(uj, uj->length);
    }

    static int ujGetVLC(ujContext* uj, ujVLCCode* vlc, unsigned char* code) {
        int value = ujShowBits(uj, 16);
        int bits = vlc[value].bits;
        if (!bits) {
            ujError = UJ_SYNTAX_ERROR;
            return 0;
        }
        ujSkipBits(uj, bits);
        value = vlc[value].code;
        if (code) *code = (unsigned char)value;
        bits = value & 15;
        if (!bits) return 0;
        value = ujGetBits(uj, bits);
        if (value < (1 << (bits - 1)))
            value += ((-1) << bits) + 1;
        return value;
    }

    UJ_INLINE void ujDecodeBlock(ujContext* uj, ujComponent* c, unsigned char* out) {
        unsigned char code = 0;
        int value, coef = 0;
        memset(uj->block, 0, sizeof(uj->block));
        c->dcpred += ujGetVLC(uj, &uj->vlctab[c->dctabsel][0], NULL);
        uj->block[0] = (c->dcpred) * uj->qtab[c->qtsel][0];
        do {
            value = ujGetVLC(uj, &uj->vlctab[c->actabsel][0], &code);
            if (!code) break;  // 0x00 接下来所有交流系数全部为0
            if (!(code & 0x0F) && (code != 0xF0))
                ujThrow(UJ_SYNTAX_ERROR);
            coef += (code >> 4) + 1;
            if (coef > 63)
                ujThrow(UJ_SYNTAX_ERROR);
            uj->block[(int)ujZZ[coef]] = value * uj->qtab[c->qtsel][coef];
        } while (coef < 63);
        for (coef = 0; coef < 64; coef += 8)
            ujRowIDCT(&uj->block[coef]);
        for (coef = 0; coef < 8; ++coef)
            ujColIDCT(&uj->block[coef], &out[coef], c->stride);
    }

    UJ_INLINE void ujDecodeScan(ujContext* uj) {
        int i, mbx, mby, sbx, sby;
        int rstcount = uj->rstinterval, nextrst = 0;
        ujComponent* c;
        ujDecodeLength(uj);
        ujCheckError();
        if (uj->length < (4 + 2 * uj->ncomp)) ujThrow(UJ_SYNTAX_ERROR);
        if (uj->pos[0] != uj->ncomp) ujThrow(UJ_UNSUPPORTED);
        ujSkip(uj, 1);
        for (i = 0, c = uj->comp; i < uj->ncomp; ++i, ++c) {
            if (uj->pos[0] != c->cid) ujThrow(UJ_SYNTAX_ERROR);
            // 大话2新地图特殊处理
            // if (uj->pos[1] & 0xEE) ujThrow(UJ_SYNTAX_ERROR);
            c->dctabsel = uj->pos[1] >> 4;
            // AC为4~7
            // c->actabsel = (uj->pos[1] & 1) | 2;
            c->actabsel = (uj->pos[1] & 3) | 4;
            ujSkip(uj, 2);
        }
        // 0x003F00
        if (uj->pos[0] || (uj->pos[1] != 63) || uj->pos[2]) ujThrow(UJ_UNSUPPORTED);

        ujSkip(uj, uj->length);

        // 大话2旧地图特殊处理
        if (uj->mapx) {
            // uj->width = uj->pos[0] + uj->pos[1] << 8;
            // uj->height = uj->pos[2] + uj->pos[3] << 8;
            uj->pos += 4;
            uj->size -= 4;
            uj->comp[0].dcpred = (short)ujDecode16Reverse(uj->pos);
            uj->pos += 2;
            uj->comp[1].dcpred = (short)ujDecode16Reverse(uj->pos);
            uj->pos += 2;
            uj->comp[2].dcpred = (short)ujDecode16Reverse(uj->pos);
            uj->pos += 2;
            int bit_pos = *uj->pos++;
            uj->size -= 7;
            ujSkipBits(uj, bit_pos);
        }
        uj->valid = 1;
        if (uj->no_decode) { ujError = __UJ_FINISHED; return; }
        uj->decoded = 1;  // mark the image as decoded now -- every subsequent error
                          // just means that the image hasn't been decoded
                          // completely
        for (mbx = mby = 0;;) {
            for (i = 0, c = uj->comp; i < uj->ncomp; ++i, ++c)
                for (sby = 0; sby < c->ssy; ++sby)
                    for (sbx = 0; sbx < c->ssx; ++sbx) {
                        ujDecodeBlock(uj, c, &c->pixels[((mby * c->ssy + sby) * c->stride + mbx * c->ssx + sbx) << 3]);
                        ujCheckError();
                    }
            if (++mbx >= uj->mbwidth) {
                mbx = 0;
                // 大话2旧地图特殊处理
                if (uj->mapx) {
                    int back = uj->bufbits / 8;
                    while (back) {
                        uj->pos--;
                        uj->size++;
                        back--;
                    }
                    uj->buf = 0;
                    uj->bufbits = 0;
                    uj->comp[0].dcpred = (short)ujDecode16Reverse(uj->pos);
                    uj->pos += 2;
                    uj->comp[1].dcpred = (short)ujDecode16Reverse(uj->pos);
                    uj->pos += 2;
                    uj->comp[2].dcpred = (short)ujDecode16Reverse(uj->pos);
                    uj->pos += 2;
                    int bit_pos = *uj->pos++;
                    uj->size -= 7;
                    ujSkipBits(uj, bit_pos);
                }
                if (++mby >= uj->mbheight) break;
            }
            if (uj->rstinterval && !(--rstcount)) {
                ujByteAlign(uj);
                i = ujGetBits(uj, 16);
                if (((i & 0xFFF8) != 0xFFD0) || ((i & 7) != nextrst))
                    ujThrow(UJ_SYNTAX_ERROR);
                nextrst = (nextrst + 1) & 7;
                rstcount = uj->rstinterval;
                for (i = 0; i < 3; ++i)
                    uj->comp[i].dcpred = 0;
            }
        }
        ujError = __UJ_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) ujClip(((x) + 64) >> 7)

    UJ_INLINE void ujUpsampleHCentered(ujComponent* c) {
        const int xmax = c->width - 3;
        unsigned char* out, * lin, * lout;
        int x, y;
        out = (unsigned char*)malloc((c->width * c->height) << 1);
        if (!out) ujThrow(UJ_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;
        free((void*)c->pixels);
        c->pixels = out;
    }

    UJ_INLINE void ujUpsampleVCentered(ujComponent* c) {
        const int w = c->width, s1 = c->stride, s2 = s1 + s1;
        unsigned char* out, * cin, * cout;
        int x, y;
        out = (unsigned char*)malloc((c->width * c->height) << 1);
        if (!out) ujThrow(UJ_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;
        free((void*)c->pixels);
        c->pixels = out;
    }

#define SF(x) ujClip(((x) + 8) >> 4)

    UJ_INLINE void ujUpsampleHCoSited(ujComponent* c) {
        const int xmax = c->width - 1;
        unsigned char* out, * lin, * lout;
        int x, y;
        out = (unsigned char*)malloc((c->width * c->height) << 1);
        if (!out) ujThrow(UJ_OUT_OF_MEM);
        lin = c->pixels;
        lout = out;
        for (y = c->height; y; --y) {
            lout[0] = lin[0];
            lout[1] = SF((lin[0] << 3) + 9 * lin[1] - lin[2]);
            lout[2] = lin[1];
            for (x = 2; x < xmax; ++x) {
                lout[(x << 1) - 1] = SF(9 * (lin[x - 1] + lin[x]) - (lin[x - 2] + lin[x + 1]));
                lout[x << 1] = lin[x];
            }
            lin += c->stride;
            lout += c->width << 1;
            lout[-3] = SF((lin[-1] << 3) + 9 * lin[-2] - lin[-3]);
            lout[-2] = lin[-1];
            lout[-1] = SF(17 * lin[-1] - lin[-2]);
        }
        c->width <<= 1;
        c->stride = c->width;
        free((void*)c->pixels);
        c->pixels = out;
    }

    UJ_INLINE void ujUpsampleVCoSited(ujComponent* c) {
        const int w = c->width, s1 = c->stride, s2 = s1 + s1;
        unsigned char* out, * cin, * cout;
        int x, y;
        out = (unsigned char*)malloc((c->width * c->height) << 1);
        if (!out) ujThrow(UJ_OUT_OF_MEM);
        for (x = 0; x < w; ++x) {
            cin = &c->pixels[x];
            cout = &out[x];
            *cout = cin[0];  cout += w;
            *cout = SF((cin[0] << 3) + 9 * cin[s1] - cin[s2]);  cout += w;
            *cout = cin[s1];  cout += w;
            cin += s1;
            for (y = c->height - 3; y; --y) {
                *cout = SF(9 * (cin[0] + cin[s1]) - (cin[-s1] + cin[s2]));  cout += w;
                *cout = cin[s1];  cout += w;
                cin += s1;
            }
            *cout = SF((cin[s1] << 3) + 9 * cin[0] - cin[-s1]);  cout += w;
            *cout = cin[-s1];  cout += w;
            *cout = SF(17 * cin[s1] - cin[0]);
        }
        c->height <<= 1;
        c->stride = c->width;
        free((void*)c->pixels);
        c->pixels = out;
    }

    UJ_INLINE void ujUpsampleFast(ujContext* uj, ujComponent* c) {
        int x, y, xshift = 0, yshift = 0;
        unsigned char* out, * lin, * lout;
        while (c->width < uj->width) { c->width <<= 1; ++xshift; }
        while (c->height < uj->height) { c->height <<= 1; ++yshift; }
        if (!xshift && !yshift) return;
        out = (unsigned char*)malloc(c->width * c->height);
        if (!out) ujThrow(UJ_OUT_OF_MEM);
        lin = c->pixels;
        lout = out;
        for (y = 0; y < c->height; ++y) {
            lin = &c->pixels[(y >> yshift) * c->stride];
            for (x = 0; x < c->width; ++x)
                lout[x] = lin[x >> xshift];
            lout += c->width;
        }
        c->stride = c->width;
        free((void*)c->pixels);
        c->pixels = out;
    }

    UJ_INLINE void ujConvert(ujContext* uj, unsigned char* pout) {
        int i;
        ujComponent* c;
        for (i = 0, c = uj->comp; i < uj->ncomp; ++i, ++c) {
            if (uj->fast_chroma) {
                ujUpsampleFast(uj, c);
                ujCheckError();
            }
            else {
                while ((c->width < uj->width) || (c->height < uj->height)) {
                    if (c->width < uj->width) {
                        if (uj->co_sited_chroma) ujUpsampleHCoSited(c);
                        else ujUpsampleHCentered(c);
                    }
                    ujCheckError();
                    if (c->height < uj->height) {
                        if (uj->co_sited_chroma) ujUpsampleVCoSited(c);
                        else ujUpsampleVCentered(c);
                    }
                    ujCheckError();
                }
            }
            if ((c->width < uj->width) || (c->height < uj->height)) ujThrow(UJ_INTERNAL_ERR);
        }
        if (uj->ncomp == 3) {
            // convert to RGB
            int x, yy;
            const unsigned char* py = uj->comp[0].pixels;
            const unsigned char* pcb = uj->comp[1].pixels;
            const unsigned char* pcr = uj->comp[2].pixels;
            for (yy = uj->height; yy; --yy) {
                for (x = 0; x < uj->width; ++x) {
                    register int y = py[x] << 8;
                    register int cb = pcb[x] - 128;
                    register int cr = pcr[x] - 128;
                    *pout++ = ujClip((y + 359 * cr + 128) >> 8);
                    *pout++ = ujClip((y - 88 * cb - 183 * cr + 128) >> 8);
                    *pout++ = ujClip((y + 454 * cb + 128) >> 8);
                }
                py += uj->comp[0].stride;
                pcb += uj->comp[1].stride;
                pcr += uj->comp[2].stride;
            }
        }
        else {
            // grayscale -> only remove stride
            unsigned char* pin = &uj->comp[0].pixels[uj->comp[0].stride];
            int y;
            for (y = uj->height - 1; y; --y) {
                memcpy(pout, pin, uj->width);
                pin += uj->comp[0].stride;
                pout += uj->width;
            }
        }
    }

    void ujDone(ujContext* uj) {
        int i;
        for (i = 0; i < 3; ++i)
            if (uj->comp[i].pixels)
                free((void*)uj->comp[i].pixels);
        if (uj->rgb)
            free((void*)uj->rgb);
    }

    void ujInit(ujContext* uj) {
        int save_no_decode = uj->no_decode;
        int save_fast_chroma = uj->fast_chroma;
        ujDone(uj);
        memset(uj, 0, sizeof(ujContext));
        uj->no_decode = save_no_decode;
        uj->fast_chroma = save_fast_chroma;
    }

    ///////////////////////////////////////////////////////////////////////////////

    UJ_INLINE unsigned short ujGetExif16(ujContext* uj, const unsigned char* p) {
        if (uj->exif_le)
            return p[0] + (p[1] << 8);
        else
            return (p[0] << 8) + p[1];
    }

    UJ_INLINE int ujGetExif32(ujContext* uj, const unsigned char* p) {
        if (uj->exif_le)
            return p[0] + (p[1] << 8) + (p[2] << 16) + (p[3] << 24);
        else
            return (p[0] << 24) + (p[1] << 16) + (p[2] << 8) + p[3];
    }

    UJ_INLINE void ujDecodeExif(ujContext* uj) {
        const unsigned char* ptr;
        int size, count, i;
        if (uj->no_decode || uj->fast_chroma) {
            ujSkipMarker(uj);
            return;
        }
        ujDecodeLength(uj);
        ujCheckError();
        ptr = uj->pos;
        size = uj->length;
        ujSkip(uj, uj->length);
        if (size < 18) return;
        if (!memcmp(ptr, "Exif\0\0II*\0", 10))
            uj->exif_le = 1;
        else if (!memcmp(ptr, "Exif\0\0MM\0*", 10))
            uj->exif_le = 0;
        else
            return;  // invalid Exif header
        i = ujGetExif32(uj, ptr + 10) + 6;
        if ((i < 14) || (i > (size - 2))) return;
        ptr += i;
        size -= i;
        count = ujGetExif16(uj, ptr);
        i = (size - 2) / 12;
        if (count > i) return;
        ptr += 2;
        while (count--) {
            if ((ujGetExif16(uj, ptr) == 0x0213) // tag = YCbCrPositioning
                && (ujGetExif16(uj, ptr + 2) == 3)  // type = SHORT
                && (ujGetExif32(uj, ptr + 4) == 1)  // length = 1
                ) {
                uj->co_sited_chroma = (ujGetExif16(uj, ptr + 8) == 2);
                return;
            }
            ptr += 12;
        }
    }

    ///////////////////////////////////////////////////////////////////////////////

    ujImage ujCreate(void) {
        ujContext* uj = (ujContext*)calloc(1, sizeof(ujContext));
        ujError = uj ? UJ_OK : UJ_OUT_OF_MEM;
        return (ujImage)uj;
    }

    void ujDisableDecoding(ujImage img) {
        ujContext* uj = (ujContext*)img;
        if (uj) {
            uj->no_decode = 1;
            ujError = UJ_OK;
        }
        else
            ujError = UJ_NO_CONTEXT;
    }

    void ujSetChromaMode(ujImage img, int mode) {
        ujContext* uj = (ujContext*)img;
        if (uj) {
            uj->fast_chroma = mode;
            ujError = UJ_OK;
        }
        else
            ujError = UJ_NO_CONTEXT;
    }

    ujImage ujDecode(ujImage img, const void* jpeg, const int size, bool mapx) {
        ujContext* uj = (ujContext*)(img ? img : ujCreate());
        if (img) ujInit(uj);
        ujError = UJ_OK;
        if (!uj)
        {
            ujError = UJ_OUT_OF_MEM; goto out;
        }
        uj->mapx = mapx;
        uj->pos = (const unsigned char*)jpeg;
        uj->size = size & 0x7FFFFFFF;
        if (uj->size < 2)
        {
            ujError = UJ_NO_JPEG; goto out;
        }
        if ((uj->pos[0] ^ 0xFF) | (uj->pos[1] ^ 0xD8))
        {
            ujError = UJ_NO_JPEG; goto out;
        }
        ujSkip(uj, 2);
        while (!ujError) {
            if ((uj->size < 2) || (uj->pos[0] != 0xFF))
            {
                ujError = UJ_SYNTAX_ERROR; goto out;
            }
            ujSkip(uj, 2);
            switch (uj->pos[-1]) {
            case 0xC0: ujDecodeSOF(uj);  break;
            case 0xC4: ujDecodeDHT(uj);  break;
            case 0xDB: ujDecodeDQT(uj);  break;
            case 0xDD: ujDecodeDRI(uj);  break;
            case 0xDA: ujDecodeScan(uj); break;
            case 0xFE: ujSkipMarker(uj); break;
            case 0xE1: ujDecodeExif(uj); break;
            default:
                if ((uj->pos[-1] & 0xF0) == 0xE0)
                    ujSkipMarker(uj);
                else
                {
                    ujError = UJ_UNSUPPORTED; goto out;
                }
            }
        }
        if (ujError == __UJ_FINISHED) ujError = UJ_OK;
    out:
        if (ujError && !uj->valid) {
            if (!img)
                ujFree(uj);
            return NULL;
        }
        return (ujImage)uj;
    }

    ujImage ujDecodeFile(ujImage img, const char* filename) {
        FILE* f; size_t size;
        void* buf;
        ujError = UJ_OK;
        f = fopen(filename, "rb");
        if (!f) {
            ujError = UJ_IO_ERROR;
            return NULL;
        }
        fseek(f, 0, SEEK_END);
        size = ftell(f);
        fseek(f, 0, SEEK_SET);
#ifdef UJ_NODECODE_BLOCK_SIZE
        if (img && ((ujContext*)img)->no_decode && (size > UJ_NODECODE_BLOCK_SIZE))
            size = UJ_NODECODE_BLOCK_SIZE;
#endif
        buf = malloc(size);
        if (!buf) {
            fclose(f);
            ujError = UJ_OUT_OF_MEM;
            return NULL;
        }
        size = fread(buf, 1, size, f);
        fclose(f);
        img = ujDecode(img, buf, (int)size, false);
        free(buf);
        return img;
    }

    ujResult ujGetError(void) {
        return ujError;
    }

    int ujIsValid(ujImage img) {
        ujContext* uj = (ujContext*)img;
        if (!uj) { ujError = UJ_NO_CONTEXT; return 0; }
        return uj->valid;
    }

    int ujGetWidth(ujImage img) {
        ujContext* uj = (ujContext*)img;
        ujError = !uj ? UJ_NO_CONTEXT : (uj->valid ? UJ_OK : UJ_NOT_DECODED);
        return ujError ? 0 : uj->width;
    }

    int ujGetHeight(ujImage img) {
        ujContext* uj = (ujContext*)img;
        ujError = !uj ? UJ_NO_CONTEXT : (uj->valid ? UJ_OK : UJ_NOT_DECODED);
        return ujError ? 0 : uj->height;
    }

    int ujIsColor(ujImage img) {
        ujContext* uj = (ujContext*)img;
        ujError = !uj ? UJ_NO_CONTEXT : (uj->valid ? UJ_OK : UJ_NOT_DECODED);
        return ujError ? 0 : (uj->ncomp != 1);
    }

    int ujGetImageSize(ujImage img) {
        ujContext* uj = (ujContext*)img;
        ujError = !uj ? UJ_NO_CONTEXT : (uj->valid ? UJ_OK : UJ_NOT_DECODED);
        return ujError ? 0 : (uj->width * uj->height * uj->ncomp);
    }

    ujPlane* ujGetPlane(ujImage img, int num) {
        ujContext* uj = (ujContext*)img;
        ujError = !uj ? UJ_NO_CONTEXT : (uj->decoded ? UJ_OK : UJ_NOT_DECODED);
        if (!ujError && (num >= uj->ncomp)) ujError = UJ_INVALID_ARG;
        return ujError ? NULL : ((ujPlane*)&uj->comp[num]);
    }

    unsigned char* ujGetImage(ujImage img, unsigned char* dest) {
        ujContext* uj = (ujContext*)img;
        ujError = !uj ? UJ_NO_CONTEXT : (uj->decoded ? UJ_OK : UJ_NOT_DECODED);
        if (ujError) return NULL;
        if (dest) {
            if (uj->rgb)
                memcpy(dest, uj->rgb, uj->width * uj->height * uj->ncomp);
            else {
                ujConvert(uj, dest);
                if (ujError) return NULL;
            }
            return dest;
        }
        else {
            if (!uj->rgb) {
                uj->rgb = (unsigned char*)malloc(uj->width * uj->height * uj->ncomp);
                if (!uj->rgb) { ujError = UJ_OUT_OF_MEM; return NULL; }
                ujConvert(uj, uj->rgb);
                if (ujError) return NULL;
            }
            return uj->rgb;
        }
    }

    void ujDestroy(ujImage img) {
        ujError = UJ_OK;
        if (!img) { ujError = UJ_NO_CONTEXT; return; }
        ujDone((ujContext*)img);
        free(img);
    }

#ifdef __cplusplus
}
#endif