ljpegdecompressor_priv.hpp

/*
 * libopenraw - ljpegdecompressor_priv.h
 *
 * Copyright (C) 2007-2022 Hubert Figuière
 *
 * This library is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see
 * <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include <string.h>
 
namespace OpenRaw {
namespace Internals {
 
/*
* The following structure stores basic information about one component.
*/
typedef struct JpegComponentInfo {
    /*
     * These values are fixed over the whole image.
     * They are read from the SOF marker.
     */
    int16_t componentId;        /* identifier for this component (0..255) */
    int16_t componentIndex; /* its index in SOF or cPtr->compInfo[]   */
 
    /*
     * Downsampling is not normally used in lossless JPEG, although
     * it is permitted by the JPEG standard (DIS). We set all sampling
     * factors to 1 in this program.
     */
    int16_t hSampFactor;        /* horizontal sampling factor */
    int16_t vSampFactor;        /* vertical sampling factor   */
 
    /*
     * Huffman table selector (0..3). The value may vary
     * between scans. It is read from the SOS marker.
     */
    int16_t dcTblNo;
} JpegComponentInfo;
 
 
/*
* One of the following structures is created for each huffman coding
* table.  We use the same structure for encoding and decoding, so there
* may be some extra fields for encoding that aren't used in the decoding
* and vice-versa.
*/
struct HuffmanTable {
    /*
     * These two fields directly represent the contents of a JPEG DHT
     * marker
     */
    uint8_t bits[17];
    uint8_t huffval[256];
 
    /*
     * The remaining fields are computed from the above to allow more
     * efficient coding and decoding.  These fields should be considered
     * private to the Huffman compression & decompression modules.
     */
    uint16_t ehufco[256];
    char ehufsi[256];
 
    uint16_t mincode[17];
    int32_t maxcode[18];
    int16_t valptr[17];
    int32_t numbits[256];
    int32_t value[256];
};
 
/*
 * One of the following structures is used to pass around the
 * decompression information.
 */
struct DecompressInfo
{
    // non copyable
    DecompressInfo(const DecompressInfo&) = delete;
    DecompressInfo& operator=(const DecompressInfo&) = delete;
 
    DecompressInfo()
        : imageWidth(0), imageHeight(0),
            dataPrecision(0), compInfo(NULL),
            numComponents(0),
            compsInScan(0),
            Ss(0), Pt(0),
            restartInterval(0), restartInRows(0),
            restartRowsToGo(0), nextRestartNum(0)
        {
            memset(&curCompInfo, 0, sizeof(curCompInfo));
            memset(&MCUmembership, 0, sizeof(MCUmembership));
            memset(&dcHuffTblPtrs, 0, sizeof(dcHuffTblPtrs));
        }
    ~DecompressInfo()
        {
            int i;
            for(i = 0; i < 4; i++) {
                if(dcHuffTblPtrs[i]) {
                    free(dcHuffTblPtrs[i]);
                }
            }
            if(compInfo) {
                free(compInfo);
            }
        }
    /*
     * Image width, height, and image data precision (bits/sample)
     * These fields are set by ReadFileHeader or ReadScanHeader
     */
    int32_t imageWidth;
    int32_t imageHeight;
    int32_t dataPrecision;
 
    /*
     * compInfo[i] describes component that appears i'th in SOF
     * numComponents is the # of color components in JPEG image.
     */
    JpegComponentInfo *compInfo;
    int16_t numComponents;
 
    /*
     * *curCompInfo[i] describes component that appears i'th in SOS.
     * compsInScan is the # of color components in current scan.
     */
    JpegComponentInfo *curCompInfo[4];
    int16_t compsInScan;
 
    /*
     * MCUmembership[i] indexes the i'th component of MCU into the
     * curCompInfo array.
     */
    int16_t MCUmembership[10];
 
    /*
     * ptrs to Huffman coding tables, or NULL if not defined
     */
    HuffmanTable *dcHuffTblPtrs[4];
 
    /*
     * prediction seletion value (PSV) and point transform parameter (Pt)
     */
    int32_t Ss;
    int32_t Pt;
 
    /*
     * In lossless JPEG, restart interval shall be an integer
     * multiple of the number of MCU in a MCU row.
     */
    int32_t restartInterval;/* MCUs per restart interval, 0 = no restart */
    int32_t restartInRows; /*if > 0, MCU rows per restart interval; 0 = no restart*/
 
    /*
     * these fields are private data for the entropy decoder
     */
    int32_t restartRowsToGo;    /* MCUs rows left in this restart interval */
    int16_t nextRestartNum; /* # of next RSTn marker (0..7) */
};
 
}
}