rockbox/apps/recorder/jpeg_common.h

/***************************************************************************
*             __________               __   ___.
*   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
*   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
*   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
*   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
*                     \/            \/     \/    \/            \/
* $Id$
*
* JPEG image viewer
* Common structs and defines for plugin and core JPEG decoders
*
* File scrolling addition (C) 2005 Alexander Spyridakis
* Copyright (C) 2004 Jörg Hohensohn aka [IDC]Dragon
* Heavily borrowed from the IJG implementation (C) Thomas G. Lane
* Small & fast downscaling IDCT (C) 2002 by Guido Vollbeding  JPEGclub.org
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/

#ifndef _JPEG_COMMON_H
#define _JPEG_COMMON_H

#include "bmp.h"

#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
#define JPEG_READ_BUF_SIZE 16
struct derived_tbl
{
    /* Basic tables: (element [0] of each array is unused) */
    long mincode[17]; /* smallest code of length k */
    long maxcode[18]; /* largest code of length k (-1 if none) */
    /* (maxcode[17] is a sentinel to ensure huff_DECODE terminates) */
    int valptr[17]; /* huffval[] index of 1st symbol of length k */

    /* Back link to public Huffman table (needed only in slow_DECODE) */
    int* pub;

    /* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of
    the input data stream.  If the next Huffman code is no more
    than HUFF_LOOKAHEAD bits long, we can obtain its length and
    the corresponding symbol directly from these tables. */
    int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */
    unsigned char look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */
};

#define QUANT_TABLE_LENGTH  64

/*
 * Conversion of full 0-255 range YCrCb to RGB:
 *   |R|   |1.000000 -0.000001  1.402000| |Y'|
 *   |G| = |1.000000 -0.334136 -0.714136| |Pb|
 *   |B|   |1.000000  1.772000  0.000000| |Pr|
 * Scaled (yields s15-bit output):
 *   |R|   |128    0  179| |Y       |
 *   |G| = |128  -43  -91| |Cb - 128|
 *   |B|   |128  227    0| |Cr - 128|
 */
#define YFAC            128
#define RVFAC           179
#define GUFAC           (-43)
#define GVFAC           (-91)
#define BUFAC           227
#define COMPONENT_SHIFT  15

struct uint8_yuv {
    uint8_t y;
    uint8_t u;
    uint8_t v;
};

union uint8_rgbyuv {
    struct uint8_yuv yuv;
    struct uint8_rgb rgb;
};

static inline int clamp_component(int x)
{
    if(x > 255) return 255;
    if(x < 0)   return 0;
    return x;
}
#include <debug.h>
static inline void yuv_to_rgb(int y, int u, int v, unsigned *r, unsigned *g, unsigned *b)
{
    int rv, guv, bu;
    y = y * YFAC + (YFAC >> 1);
    u = u - 128;
    v = v - 128;
    rv = RVFAC * v;
    guv = GUFAC * u + GVFAC * v;
    bu = BUFAC * u;
    *r = clamp_component((y + rv) / YFAC);
    *g = clamp_component((y + guv) / YFAC);
    *b = clamp_component((y + bu) / YFAC);
}

/* for type of Huffman table */
#define DC_LEN 28
#define AC_LEN 178

struct huffman_table
{   /* length and code according to JFIF format */
    int huffmancodes_dc[DC_LEN];
    int huffmancodes_ac[AC_LEN];
};

struct frame_component
{
    int ID;
    int horizontal_sampling;
    int vertical_sampling;
    int quanttable_select;
};

struct scan_component
{
    int ID;
    int DC_select;
    int AC_select;
};

struct bitstream
{
    unsigned long get_buffer; /* current bit-extraction buffer */
    int bits_left; /* # of unused bits in it */
    unsigned char* next_input_byte;
    unsigned char* input_end; /* upper limit +1 */
};

/* possible return flags for process_markers() */
#define HUFFTAB   0x0001 /* with huffman table */
#define QUANTTAB  0x0002 /* with quantization table */
#define APP0_JFIF 0x0004 /* with APP0 segment following JFIF standard */
#define SOF0      0x0010 /* with SOF0-Segment */
#define DHT       0x0020 /* with Definition of huffman tables */
#define SOS       0x0040 /* with Start-of-Scan segment */
#define DQT       0x0080 /* with definition of quantization table */

#endif /* _JPEG_COMMON_H */