jpeg.c

Go to the documentation of this file.

/*
    Copyright (C) 2002  Mathieu Olivier
 
    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 program 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 General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with this program; if not, write to:
 
        Free Software Foundation, Inc.
        59 Temple Place - Suite 330
        Boston, MA  02111-1307, USA
 
*/
 
 
#include "darkplaces.h"
#include "cl_screen.h"
#include "image.h"
#include "jpeg.h"
#include "image_png.h"
 
extern cvar_t sv_writepicture_quality;
cvar_t r_texture_jpeg_fastpicmip = {CF_CLIENT | CF_ARCHIVE, "r_texture_jpeg_fastpicmip", "1", "perform gl_picmip during decompression for JPEG files (faster)"};
 
// jboolean is unsigned char instead of int on Win32
#ifdef WIN32
typedef unsigned char jboolean;
#else
typedef int jboolean;
#endif
 
#ifdef LINK_TO_LIBJPEG
#include <jpeglib.h>
#define qjpeg_create_compress jpeg_create_compress
#define qjpeg_create_decompress jpeg_create_decompress
#define qjpeg_destroy_compress jpeg_destroy_compress
#define qjpeg_destroy_decompress jpeg_destroy_decompress
#define qjpeg_finish_compress jpeg_finish_compress
#define qjpeg_finish_decompress jpeg_finish_decompress
#define qjpeg_resync_to_restart jpeg_resync_to_restart
#define qjpeg_read_header jpeg_read_header
#define qjpeg_read_scanlines jpeg_read_scanlines
#define qjpeg_set_defaults jpeg_set_defaults
#define qjpeg_set_quality jpeg_set_quality
#define qjpeg_start_compress jpeg_start_compress
#define qjpeg_start_decompress jpeg_start_decompress
#define qjpeg_std_error jpeg_std_error
#define qjpeg_write_scanlines jpeg_write_scanlines
#define qjpeg_simple_progression jpeg_simple_progression
#define jpeg_dll true
#else
/*
=================================================================
 
  Minimal set of definitions from the JPEG lib
 
  WARNING: for a matter of simplicity, several pointer types are
  casted to "void*", and most enumerated values are not included
 
=================================================================
*/
 
typedef void *j_common_ptr;
typedef struct jpeg_compress_struct *j_compress_ptr;
typedef struct jpeg_decompress_struct *j_decompress_ptr;
 
#define JPEG_LIB_VERSION  62  // Version 6b
 
typedef enum
{
    JCS_UNKNOWN,
    JCS_GRAYSCALE,
    JCS_RGB,
    JCS_YCbCr,
    JCS_CMYK,
    JCS_YCCK
} J_COLOR_SPACE;
typedef enum {JPEG_DUMMY1} J_DCT_METHOD;
typedef enum {JPEG_DUMMY2} J_DITHER_MODE;
typedef unsigned int JDIMENSION;
 
#define JPOOL_PERMANENT 0   // lasts until master record is destroyed
#define JPOOL_IMAGE     1   // lasts until done with image/datastream
 
#define JPEG_EOI    0xD9  // EOI marker code
 
#define JMSG_STR_PARM_MAX  80
 
#define DCTSIZE2 64
#define NUM_QUANT_TBLS 4
#define NUM_HUFF_TBLS 4
#define NUM_ARITH_TBLS 16
#define MAX_COMPS_IN_SCAN 4
#define C_MAX_BLOCKS_IN_MCU 10
#define D_MAX_BLOCKS_IN_MCU 10
 
struct jpeg_memory_mgr
{
  void* (*alloc_small) (j_common_ptr cinfo, int pool_id, size_t sizeofobject);
  void (*_reserve_space_for_alloc_large) (void *dummy, ...);
  void (*_reserve_space_for_alloc_sarray) (void *dummy, ...);
  void (*_reserve_space_for_alloc_barray) (void *dummy, ...);
  void (*_reserve_space_for_request_virt_sarray) (void *dummy, ...);
  void (*_reserve_space_for_request_virt_barray) (void *dummy, ...);
  void (*_reserve_space_for_realize_virt_arrays) (void *dummy, ...);
  void (*_reserve_space_for_access_virt_sarray) (void *dummy, ...);
  void (*_reserve_space_for_access_virt_barray) (void *dummy, ...);
  void (*_reserve_space_for_free_pool) (void *dummy, ...);
  void (*_reserve_space_for_self_destruct) (void *dummy, ...);
 
  long max_memory_to_use;
  long max_alloc_chunk;
};
 
struct jpeg_error_mgr
{
    void (*error_exit) (j_common_ptr cinfo);
    void (*emit_message) (j_common_ptr cinfo, int msg_level);
    void (*output_message) (j_common_ptr cinfo);
    void (*format_message) (j_common_ptr cinfo, char * buffer);
    void (*reset_error_mgr) (j_common_ptr cinfo);
    int msg_code;
    union {
        int i[8];
        char s[JMSG_STR_PARM_MAX];
    } msg_parm;
    int trace_level;
    long num_warnings;
    const char * const * jpeg_message_table;
    int last_jpeg_message;
    const char * const * addon_message_table;
    int first_addon_message;
    int last_addon_message;
};
 
struct jpeg_source_mgr
{
    const unsigned char *next_input_byte;
    size_t bytes_in_buffer;
 
    void (*init_source) (j_decompress_ptr cinfo);
    jboolean (*fill_input_buffer) (j_decompress_ptr cinfo);
    void (*skip_input_data) (j_decompress_ptr cinfo, long num_bytes);
    jboolean (*resync_to_restart) (j_decompress_ptr cinfo, int desired);
    void (*term_source) (j_decompress_ptr cinfo);
};
 
typedef struct {
  /* These values are fixed over the whole image. */
  /* For compression, they must be supplied by parameter setup; */
  /* for decompression, they are read from the SOF marker. */
  int component_id;             /* identifier for this component (0..255) */
  int component_index;          /* its index in SOF or cinfo->comp_info[] */
  int h_samp_factor;            /* horizontal sampling factor (1..4) */
  int v_samp_factor;            /* vertical sampling factor (1..4) */
  int quant_tbl_no;             /* quantization table selector (0..3) */
  /* These values may vary between scans. */
  /* For compression, they must be supplied by parameter setup; */
  /* for decompression, they are read from the SOS marker. */
  /* The decompressor output side may not use these variables. */
  int dc_tbl_no;                /* DC entropy table selector (0..3) */
  int ac_tbl_no;                /* AC entropy table selector (0..3) */
 
  /* Remaining fields should be treated as private by applications. */
 
  /* These values are computed during compression or decompression startup: */
  /* Component's size in DCT blocks.
   * Any dummy blocks added to complete an MCU are not counted; therefore
   * these values do not depend on whether a scan is interleaved or not.
   */
  JDIMENSION width_in_blocks;
  JDIMENSION height_in_blocks;
  /* Size of a DCT block in samples.  Always DCTSIZE for compression.
   * For decompression this is the size of the output from one DCT block,
   * reflecting any scaling we choose to apply during the IDCT step.
   * Values of 1,2,4,8 are likely to be supported.  Note that different
   * components may receive different IDCT scalings.
   */
  int DCT_scaled_size;
  /* The downsampled dimensions are the component's actual, unpadded number
   * of samples at the main buffer (preprocessing/compression interface), thus
   * downsampled_width = ceil(image_width * Hi/Hmax)
   * and similarly for height.  For decompression, IDCT scaling is included, so
   * downsampled_width = ceil(image_width * Hi/Hmax * DCT_scaled_size/DCTSIZE)
   */
  JDIMENSION downsampled_width;  /* actual width in samples */
  JDIMENSION downsampled_height; /* actual height in samples */
  /* This flag is used only for decompression.  In cases where some of the
   * components will be ignored (eg grayscale output from YCbCr image),
   * we can skip most computations for the unused components.
   */
  jboolean component_needed;     /* do we need the value of this component? */
 
  /* These values are computed before starting a scan of the component. */
  /* The decompressor output side may not use these variables. */
  int MCU_width;                /* number of blocks per MCU, horizontally */
  int MCU_height;               /* number of blocks per MCU, vertically */
  int MCU_blocks;               /* MCU_width * MCU_height */
  int MCU_sample_width;         /* MCU width in samples, MCU_width*DCT_scaled_size */
  int last_col_width;           /* # of non-dummy blocks across in last MCU */
  int last_row_height;          /* # of non-dummy blocks down in last MCU */
 
  /* Saved quantization table for component; NULL if none yet saved.
   * See jdinput.c comments about the need for this information.
   * This field is currently used only for decompression.
   */
  void *quant_table;
 
  /* Private per-component storage for DCT or IDCT subsystem. */
  void * dct_table;
} jpeg_component_info;
 
struct jpeg_decompress_struct
{
    struct jpeg_error_mgr *err;     // USED
    struct jpeg_memory_mgr *mem;    // USED
 
    void *progress;
    void *client_data;
    jboolean is_decompressor;
    int global_state;
 
    struct jpeg_source_mgr *src;    // USED
    JDIMENSION image_width;         // USED
    JDIMENSION image_height;        // USED
 
    int num_components;
    J_COLOR_SPACE jpeg_color_space;
    J_COLOR_SPACE out_color_space;
    unsigned int scale_num, scale_denom;
    double output_gamma;
    jboolean buffered_image;
    jboolean raw_data_out;
    J_DCT_METHOD dct_method;
    jboolean do_fancy_upsampling;
    jboolean do_block_smoothing;
    jboolean quantize_colors;
    J_DITHER_MODE dither_mode;
    jboolean two_pass_quantize;
    int desired_number_of_colors;
    jboolean enable_1pass_quant;
    jboolean enable_external_quant;
    jboolean enable_2pass_quant;
    JDIMENSION output_width;
 
    JDIMENSION output_height;   // USED
 
    int out_color_components;
 
    int output_components;      // USED
 
    int rec_outbuf_height;
    int actual_number_of_colors;
    void *colormap;
 
    JDIMENSION output_scanline; // USED
 
    int input_scan_number;
    JDIMENSION input_iMCU_row;
    int output_scan_number;
    JDIMENSION output_iMCU_row;
    int (*coef_bits)[DCTSIZE2];
    void *quant_tbl_ptrs[NUM_QUANT_TBLS];
    void *dc_huff_tbl_ptrs[NUM_HUFF_TBLS];
    void *ac_huff_tbl_ptrs[NUM_HUFF_TBLS];
    int data_precision;
    jpeg_component_info *comp_info;
    jboolean progressive_mode;
    jboolean arith_code;
    unsigned char arith_dc_L[NUM_ARITH_TBLS];
    unsigned char arith_dc_U[NUM_ARITH_TBLS];
    unsigned char arith_ac_K[NUM_ARITH_TBLS];
    unsigned int restart_interval;
    jboolean saw_JFIF_marker;
    unsigned char JFIF_major_version;
    unsigned char JFIF_minor_version;
    unsigned char density_unit;
    unsigned short X_density;
    unsigned short Y_density;
    jboolean saw_Adobe_marker;
    unsigned char Adobe_transform;
    jboolean CCIR601_sampling;
    void *marker_list;
    int max_h_samp_factor;
    int max_v_samp_factor;
    int min_DCT_scaled_size;
    JDIMENSION total_iMCU_rows;
    void *sample_range_limit;
    int comps_in_scan;
    jpeg_component_info *cur_comp_info[MAX_COMPS_IN_SCAN];
    JDIMENSION MCUs_per_row;
    JDIMENSION MCU_rows_in_scan;
    int blocks_in_MCU;
    int MCU_membership[D_MAX_BLOCKS_IN_MCU];
    int Ss, Se, Ah, Al;
    int unread_marker;
    void *master;
    void *main;
    void *coef;
    void *post;
    void *inputctl;
    void *marker;
    void *entropy;
    void *idct;
    void *upsample;
    void *cconvert;
    void *cquantize;
};
 
 
struct jpeg_compress_struct
{
    struct jpeg_error_mgr *err;
    struct jpeg_memory_mgr *mem;
    void *progress;
    void *client_data;
    jboolean is_decompressor;
    int global_state;
 
    void *dest;
    JDIMENSION image_width;
    JDIMENSION image_height;
    int input_components;
    J_COLOR_SPACE in_color_space;
    double input_gamma;
    int data_precision;
 
    int num_components;
    J_COLOR_SPACE jpeg_color_space;
    jpeg_component_info *comp_info;
    void *quant_tbl_ptrs[NUM_QUANT_TBLS];
    void *dc_huff_tbl_ptrs[NUM_HUFF_TBLS];
    void *ac_huff_tbl_ptrs[NUM_HUFF_TBLS];
    unsigned char arith_dc_L[NUM_ARITH_TBLS];
    unsigned char arith_dc_U[NUM_ARITH_TBLS];
    unsigned char arith_ac_K[NUM_ARITH_TBLS];
 
    int num_scans;
    const void *scan_info;
    jboolean raw_data_in;
    jboolean arith_code;
    jboolean optimize_coding;
    jboolean CCIR601_sampling;
    int smoothing_factor;
    J_DCT_METHOD dct_method;
 
    unsigned int restart_interval;
    int restart_in_rows;
 
    jboolean write_JFIF_header;
    unsigned char JFIF_major_version;
    unsigned char JFIF_minor_version;
    unsigned char density_unit;
    unsigned short X_density;
    unsigned short Y_density;
    jboolean write_Adobe_marker;
    JDIMENSION next_scanline;
 
    jboolean progressive_mode;
    int max_h_samp_factor;
    int max_v_samp_factor;
    JDIMENSION total_iMCU_rows;
    int comps_in_scan;
    jpeg_component_info *cur_comp_info[MAX_COMPS_IN_SCAN];
    JDIMENSION MCUs_per_row;
    JDIMENSION MCU_rows_in_scan;
    int blocks_in_MCU;
    int MCU_membership[C_MAX_BLOCKS_IN_MCU];
    int Ss, Se, Ah, Al;
 
    void *master;
    void *main;
    void *prep;
    void *coef;
    void *marker;
    void *cconvert;
    void *downsample;
    void *fdct;
    void *entropy;
    void *script_space;
    int script_space_size;
};
 
struct jpeg_destination_mgr
{
    unsigned char* next_output_byte;
    size_t free_in_buffer;
 
    void (*init_destination) (j_compress_ptr cinfo);
    jboolean (*empty_output_buffer) (j_compress_ptr cinfo);
    void (*term_destination) (j_compress_ptr cinfo);
};
 
 
/*
=================================================================
 
  DarkPlaces definitions
 
=================================================================
*/
 
// Functions exported from libjpeg
#define qjpeg_create_compress(cinfo) \
    qjpeg_CreateCompress((cinfo), JPEG_LIB_VERSION, (size_t) sizeof(struct jpeg_compress_struct))
#define qjpeg_create_decompress(cinfo) \
    qjpeg_CreateDecompress((cinfo), JPEG_LIB_VERSION, (size_t) sizeof(struct jpeg_decompress_struct))
 
static void (*qjpeg_CreateCompress) (j_compress_ptr cinfo, int version, size_t structsize);
static void (*qjpeg_CreateDecompress) (j_decompress_ptr cinfo, int version, size_t structsize);
static void (*qjpeg_destroy_compress) (j_compress_ptr cinfo);
static void (*qjpeg_destroy_decompress) (j_decompress_ptr cinfo);
static void (*qjpeg_finish_compress) (j_compress_ptr cinfo);
static jboolean (*qjpeg_finish_decompress) (j_decompress_ptr cinfo);
static jboolean (*qjpeg_resync_to_restart) (j_decompress_ptr cinfo, int desired);
static int (*qjpeg_read_header) (j_decompress_ptr cinfo, jboolean require_image);
static JDIMENSION (*qjpeg_read_scanlines) (j_decompress_ptr cinfo, unsigned char** scanlines, JDIMENSION max_lines);
static void (*qjpeg_set_defaults) (j_compress_ptr cinfo);
static void (*qjpeg_set_quality) (j_compress_ptr cinfo, int quality, jboolean force_baseline);
static jboolean (*qjpeg_start_compress) (j_compress_ptr cinfo, jboolean write_all_tables);
static jboolean (*qjpeg_start_decompress) (j_decompress_ptr cinfo);
static struct jpeg_error_mgr* (*qjpeg_std_error) (struct jpeg_error_mgr *err);
static JDIMENSION (*qjpeg_write_scanlines) (j_compress_ptr cinfo, unsigned char** scanlines, JDIMENSION num_lines);
static void (*qjpeg_simple_progression) (j_compress_ptr cinfo);
 
static dllfunction_t jpegfuncs[] =
{
    {"jpeg_CreateCompress",     (void **) &qjpeg_CreateCompress},
    {"jpeg_CreateDecompress",   (void **) &qjpeg_CreateDecompress},
    {"jpeg_destroy_compress",   (void **) &qjpeg_destroy_compress},
    {"jpeg_destroy_decompress", (void **) &qjpeg_destroy_decompress},
    {"jpeg_finish_compress",    (void **) &qjpeg_finish_compress},
    {"jpeg_finish_decompress",  (void **) &qjpeg_finish_decompress},
    {"jpeg_resync_to_restart",  (void **) &qjpeg_resync_to_restart},
    {"jpeg_read_header",        (void **) &qjpeg_read_header},
    {"jpeg_read_scanlines",     (void **) &qjpeg_read_scanlines},
    {"jpeg_set_defaults",       (void **) &qjpeg_set_defaults},
    {"jpeg_set_quality",        (void **) &qjpeg_set_quality},
    {"jpeg_start_compress",     (void **) &qjpeg_start_compress},
    {"jpeg_start_decompress",   (void **) &qjpeg_start_decompress},
    {"jpeg_std_error",          (void **) &qjpeg_std_error},
    {"jpeg_write_scanlines",    (void **) &qjpeg_write_scanlines},
    {"jpeg_simple_progression", (void **) &qjpeg_simple_progression},
    {NULL, NULL}
};
 
// Handle for JPEG DLL
dllhandle_t jpeg_dll = NULL;
qbool jpeg_tried_loading = 0;
#endif
 
static unsigned char jpeg_eoi_marker [2] = {0xFF, JPEG_EOI};
static jmp_buf error_in_jpeg;
static qbool jpeg_toolarge;
 
// Our own output manager for JPEG compression
typedef struct
{
    struct jpeg_destination_mgr pub;
 
    qfile_t* outfile;
    unsigned char* buffer;
    size_t bufsize; // used if outfile is NULL
} my_destination_mgr;
typedef my_destination_mgr* my_dest_ptr;
 
 
/*
=================================================================
 
  DLL load & unload
 
=================================================================
*/
 
/*
====================
JPEG_OpenLibrary
 
Try to load the JPEG DLL
====================
*/
qbool JPEG_OpenLibrary (void)
{
#ifdef LINK_TO_LIBJPEG
    return true;
#else
    const char* dllnames [] =
    {
#if defined(WIN32)
        "libjpeg.dll",
#elif defined(MACOSX)
        "libjpeg.62.dylib",
#else
        "libjpeg.so.62",
        "libjpeg.so",
#endif
        NULL
    };
 
    // Already loaded?
    if (jpeg_dll)
        return true;
 
    if (jpeg_tried_loading) // only try once
        return false;
 
    jpeg_tried_loading = true;
 
#ifdef __ANDROID__
    // loading the native Android libjpeg.so causes crashes
    Con_Printf("Not opening libjpeg.so dynamically on Android - use LINK_TO_LIBJPEG instead if it is needed.\n");
    return false;
#endif
 
    // Load the DLL
    return Sys_LoadDependency (dllnames, &jpeg_dll, jpegfuncs);
#endif
}
 
 
/*
====================
JPEG_CloseLibrary
 
Unload the JPEG DLL
====================
*/
void JPEG_CloseLibrary (void)
{
#ifndef LINK_TO_LIBJPEG
    Sys_FreeLibrary (&jpeg_dll);
    jpeg_tried_loading = false; // allow retry
#endif
}
 
 
/*
=================================================================
 
    JPEG decompression
 
=================================================================
*/
 
static void JPEG_Noop (j_decompress_ptr cinfo) {}
 
static jboolean JPEG_FillInputBuffer (j_decompress_ptr cinfo)
{
    // Insert a fake EOI marker
    cinfo->src->next_input_byte = jpeg_eoi_marker;
    cinfo->src->bytes_in_buffer = 2;
 
    return true;
}
 
static void JPEG_SkipInputData (j_decompress_ptr cinfo, long num_bytes)
{
    if (cinfo->src->bytes_in_buffer <= (unsigned long)num_bytes)
    {
        cinfo->src->bytes_in_buffer = 0;
        return;
    }
 
    cinfo->src->next_input_byte += num_bytes;
    cinfo->src->bytes_in_buffer -= num_bytes;
}
 
static void JPEG_MemSrc (j_decompress_ptr cinfo, const unsigned char *buffer, size_t filesize)
{
    cinfo->src = (struct jpeg_source_mgr *)cinfo->mem->alloc_small ((j_common_ptr) cinfo, JPOOL_PERMANENT, sizeof (struct jpeg_source_mgr));
 
    cinfo->src->next_input_byte = buffer;
    cinfo->src->bytes_in_buffer = filesize;
 
    cinfo->src->init_source = JPEG_Noop;
    cinfo->src->fill_input_buffer = JPEG_FillInputBuffer;
    cinfo->src->skip_input_data = JPEG_SkipInputData;
    cinfo->src->resync_to_restart = qjpeg_resync_to_restart; // use the default method
    cinfo->src->term_source = JPEG_Noop;
}
 
static void JPEG_ErrorExit (j_common_ptr cinfo)
{
    ((struct jpeg_decompress_struct*)cinfo)->err->output_message (cinfo);
    longjmp(error_in_jpeg, 1);
}
 
 
/*
====================
JPEG_LoadImage
 
Load a JPEG image into a BGRA buffer
====================
*/
unsigned char* JPEG_LoadImage_BGRA (const unsigned char *f, int filesize, int *miplevel)
{
    struct jpeg_decompress_struct cinfo;
    struct jpeg_error_mgr jerr;
    unsigned char *image_buffer = NULL, *scanline = NULL;
    unsigned int line;
    int submip = 0;
 
    // No DLL = no JPEGs
    if (!jpeg_dll)
        return NULL;
 
    if(miplevel && r_texture_jpeg_fastpicmip.integer)
        submip = bound(0, *miplevel, 3);
 
    cinfo.err = qjpeg_std_error (&jerr);
    qjpeg_create_decompress (&cinfo);
    if(setjmp(error_in_jpeg))
        goto error_caught;
    cinfo.err = qjpeg_std_error (&jerr);
    cinfo.err->error_exit = JPEG_ErrorExit;
    JPEG_MemSrc (&cinfo, f, filesize);
    qjpeg_read_header (&cinfo, true);
    cinfo.scale_num = 1;
    cinfo.scale_denom = (1 << submip);
    qjpeg_start_decompress (&cinfo);
 
    image_width = cinfo.output_width;
    image_height = cinfo.output_height;
 
    if (image_width > 32768 || image_height > 32768 || image_width <= 0 || image_height <= 0)
    {
        Con_Printf("JPEG_LoadImage: invalid image size %ix%i\n", image_width, image_height);
        return NULL;
    }
 
    image_buffer = (unsigned char *)Mem_Alloc(tempmempool, image_width * image_height * 4);
    scanline = (unsigned char *)Mem_Alloc(tempmempool, image_width * cinfo.output_components);
    if (!image_buffer || !scanline)
    {
        if (image_buffer)
            Mem_Free (image_buffer);
        if (scanline)
            Mem_Free (scanline);
 
        Con_Printf("JPEG_LoadImage: not enough memory for %i by %i image\n", image_width, image_height);
        qjpeg_finish_decompress (&cinfo);
        qjpeg_destroy_decompress (&cinfo);
        return NULL;
    }
 
    // Decompress the image, line by line
    line = 0;
    while (cinfo.output_scanline < cinfo.output_height)
    {
        unsigned char *buffer_ptr;
        int ind;
 
        qjpeg_read_scanlines (&cinfo, &scanline, 1);
 
        // Convert the image to BGRA
        switch (cinfo.output_components)
        {
            // RGB images
            case 3:
                buffer_ptr = &image_buffer[image_width * line * 4];
                for (ind = 0; ind < image_width * 3; ind += 3, buffer_ptr += 4)
                {
                    buffer_ptr[2] = scanline[ind];
                    buffer_ptr[1] = scanline[ind + 1];
                    buffer_ptr[0] = scanline[ind + 2];
                    buffer_ptr[3] = 255;
                }
                break;
 
            // Greyscale images (default to it, just in case)
            case 1:
            default:
                buffer_ptr = &image_buffer[image_width * line * 4];
                for (ind = 0; ind < image_width; ind++, buffer_ptr += 4)
                {
                    buffer_ptr[0] = scanline[ind];
                    buffer_ptr[1] = scanline[ind];
                    buffer_ptr[2] = scanline[ind];
                    buffer_ptr[3] = 255;
                }
        }
 
        line++;
    }
    Mem_Free (scanline); scanline = NULL;
 
    qjpeg_finish_decompress (&cinfo);
    qjpeg_destroy_decompress (&cinfo);
 
    if(miplevel)
        *miplevel -= submip;
 
    return image_buffer;
 
error_caught:
    if(scanline)
        Mem_Free (scanline);
    if(image_buffer)
        Mem_Free (image_buffer);
    qjpeg_destroy_decompress (&cinfo);
    return NULL;
}
 
 
/*
=================================================================
 
  JPEG compression
 
=================================================================
*/
 
#define JPEG_OUTPUT_BUF_SIZE 4096
static void JPEG_InitDestination (j_compress_ptr cinfo)
{
    my_dest_ptr dest = (my_dest_ptr)cinfo->dest;
    dest->buffer = (unsigned char*)cinfo->mem->alloc_small ((j_common_ptr) cinfo, JPOOL_IMAGE, JPEG_OUTPUT_BUF_SIZE * sizeof(unsigned char));
    dest->pub.next_output_byte = dest->buffer;
    dest->pub.free_in_buffer = JPEG_OUTPUT_BUF_SIZE;
}
 
static jboolean JPEG_EmptyOutputBuffer (j_compress_ptr cinfo)
{
    my_dest_ptr dest = (my_dest_ptr)cinfo->dest;
 
    if (FS_Write (dest->outfile, dest->buffer, JPEG_OUTPUT_BUF_SIZE) != (size_t) JPEG_OUTPUT_BUF_SIZE)
        longjmp(error_in_jpeg, 1);
 
    dest->pub.next_output_byte = dest->buffer;
    dest->pub.free_in_buffer = JPEG_OUTPUT_BUF_SIZE;
    return true;
}
 
static void JPEG_TermDestination (j_compress_ptr cinfo)
{
    my_dest_ptr dest = (my_dest_ptr)cinfo->dest;
    size_t datacount = JPEG_OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
 
    // Write any data remaining in the buffer
    if (datacount > 0)
        if (FS_Write (dest->outfile, dest->buffer, datacount) != (fs_offset_t)datacount)
            longjmp(error_in_jpeg, 1);
}
 
static void JPEG_FileDest (j_compress_ptr cinfo, qfile_t* outfile)
{
    my_dest_ptr dest;
 
    // First time for this JPEG object?
    if (cinfo->dest == NULL)
        cinfo->dest = (struct jpeg_destination_mgr *)(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, sizeof(my_destination_mgr));
 
    dest = (my_dest_ptr)cinfo->dest;
    dest->pub.init_destination = JPEG_InitDestination;
    dest->pub.empty_output_buffer = JPEG_EmptyOutputBuffer;
    dest->pub.term_destination = JPEG_TermDestination;
    dest->outfile = outfile;
}
 
static void JPEG_Mem_InitDestination (j_compress_ptr cinfo)
{
    my_dest_ptr dest = (my_dest_ptr)cinfo->dest;
    dest->pub.next_output_byte = dest->buffer;
    dest->pub.free_in_buffer = dest->bufsize;
}
 
static jboolean JPEG_Mem_EmptyOutputBuffer (j_compress_ptr cinfo)
{
    my_dest_ptr dest = (my_dest_ptr)cinfo->dest;
    jpeg_toolarge = true;
    dest->pub.next_output_byte = dest->buffer;
    dest->pub.free_in_buffer = dest->bufsize;
    return true;
}
 
static void JPEG_Mem_TermDestination (j_compress_ptr cinfo)
{
    my_dest_ptr dest = (my_dest_ptr)cinfo->dest;
    dest->bufsize = dest->pub.next_output_byte - dest->buffer;
}
static void JPEG_MemDest (j_compress_ptr cinfo, void* buf, size_t bufsize)
{
    my_dest_ptr dest;
 
    // First time for this JPEG object?
    if (cinfo->dest == NULL)
        cinfo->dest = (struct jpeg_destination_mgr *)(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, sizeof(my_destination_mgr));
 
    dest = (my_dest_ptr)cinfo->dest;
    dest->pub.init_destination = JPEG_Mem_InitDestination;
    dest->pub.empty_output_buffer = JPEG_Mem_EmptyOutputBuffer;
    dest->pub.term_destination = JPEG_Mem_TermDestination;
    dest->outfile = NULL;
 
    dest->buffer = (unsigned char *) buf;
    dest->bufsize = bufsize;
}
 
 
/*
====================
JPEG_SaveImage_preflipped
 
Save a preflipped JPEG image to a file
====================
*/
qbool JPEG_SaveImage_preflipped (const char *filename, int width, int height, unsigned char *data)
{
    struct jpeg_compress_struct cinfo;
    struct jpeg_error_mgr jerr;
    unsigned char *scanline;
    unsigned int offset, linesize;
    qfile_t* file;
 
    // No DLL = no JPEGs
    if (!jpeg_dll)
    {
        Con_Print("You need the libjpeg library to save JPEG images\n");
        return false;
    }
 
    // Open the file
    file = FS_OpenRealFile(filename, "wb", true);
    if (!file)
        return false;
 
    if(setjmp(error_in_jpeg))
        goto error_caught;
    cinfo.err = qjpeg_std_error (&jerr);
    cinfo.err->error_exit = JPEG_ErrorExit;
 
    qjpeg_create_compress (&cinfo);
    JPEG_FileDest (&cinfo, file);
 
    // Set the parameters for compression
    cinfo.image_width = width;
    cinfo.image_height = height;
    cinfo.in_color_space = JCS_RGB;
    cinfo.input_components = 3;
    qjpeg_set_defaults (&cinfo);
    qjpeg_set_quality (&cinfo, (int)(scr_screenshot_jpeg_quality.value * 100), true);
    qjpeg_simple_progression (&cinfo);
 
    // turn off subsampling (to make text look better)
    cinfo.optimize_coding = 1;
    cinfo.comp_info[0].h_samp_factor = 1;
    cinfo.comp_info[0].v_samp_factor = 1;
    cinfo.comp_info[1].h_samp_factor = 1;
    cinfo.comp_info[1].v_samp_factor = 1;
    cinfo.comp_info[2].h_samp_factor = 1;
    cinfo.comp_info[2].v_samp_factor = 1;
 
    qjpeg_start_compress (&cinfo, true);
 
    // Compress each scanline
    linesize = cinfo.image_width * 3;
    offset = linesize * (cinfo.image_height - 1);
    while (cinfo.next_scanline < cinfo.image_height)
    {
        scanline = &data[offset - cinfo.next_scanline * linesize];
 
        qjpeg_write_scanlines (&cinfo, &scanline, 1);
    }
 
    qjpeg_finish_compress (&cinfo);
    qjpeg_destroy_compress (&cinfo);
 
    FS_Close (file);
    return true;
 
error_caught:
    qjpeg_destroy_compress (&cinfo);
    FS_Close (file);
    return false;
}
 
static size_t JPEG_try_SaveImage_to_Buffer (struct jpeg_compress_struct *cinfo, char *jpegbuf, size_t jpegsize, int quality, int width, int height, unsigned char *data)
{
    unsigned char *scanline;
    unsigned int linesize;
 
    jpeg_toolarge = false;
    JPEG_MemDest (cinfo, jpegbuf, jpegsize);
 
    // Set the parameters for compression
    cinfo->image_width = width;
    cinfo->image_height = height;
    cinfo->in_color_space = JCS_RGB;
    cinfo->input_components = 3;
    qjpeg_set_defaults (cinfo);
    qjpeg_set_quality (cinfo, quality, false);
 
    cinfo->comp_info[0].h_samp_factor = 2;
    cinfo->comp_info[0].v_samp_factor = 2;
    cinfo->comp_info[1].h_samp_factor = 1;
    cinfo->comp_info[1].v_samp_factor = 1;
    cinfo->comp_info[2].h_samp_factor = 1;
    cinfo->comp_info[2].v_samp_factor = 1;
    cinfo->optimize_coding = 1;
 
    qjpeg_start_compress (cinfo, true);
 
    // Compress each scanline
    linesize = width * 3;
    while (cinfo->next_scanline < cinfo->image_height)
    {
        scanline = &data[cinfo->next_scanline * linesize];
 
        qjpeg_write_scanlines (cinfo, &scanline, 1);
    }
 
    qjpeg_finish_compress (cinfo);
 
    if(jpeg_toolarge)
        return 0;
 
    return ((my_dest_ptr) cinfo->dest)->bufsize;
}
 
size_t JPEG_SaveImage_to_Buffer (char *jpegbuf, size_t jpegsize, int width, int height, unsigned char *data)
{
    struct jpeg_compress_struct cinfo;
    struct jpeg_error_mgr jerr;
 
    int quality;
    int quality_guess;
    size_t result;
 
    // No DLL = no JPEGs
    if (!jpeg_dll)
    {
        Con_Print("You need the libjpeg library to save JPEG images\n");
        return false;
    }
 
    if(setjmp(error_in_jpeg))
        goto error_caught;
    cinfo.err = qjpeg_std_error (&jerr);
    cinfo.err->error_exit = JPEG_ErrorExit;
 
    qjpeg_create_compress (&cinfo);
 
#if 0
    // used to get the formula below
    {
        char buf[1048576];
        unsigned char *img;
        int i;
 
        img = Mem_Alloc(tempmempool, width * height * 3);
        for(i = 0; i < width * height * 3; ++i)
            img[i] = rand() & 0xFF;
 
        for(i = 0; i <= 100; ++i)
        {
            Con_Printf("! %d %d %d %d\n", width, height, i, (int) JPEG_try_SaveImage_to_Buffer(&cinfo, buf, sizeof(buf), i, width, height, img));
        }
 
        Mem_Free(img);
    }
#endif
 
    //quality_guess = (int)((100 * jpegsize - 41000) / (width*height) + 2); // fits random data
    quality_guess   = (int)((256 * jpegsize - 81920) / (width*height) - 8); // fits Nexuiz's/Xonotic's map pictures
 
    quality_guess = bound(0, quality_guess, 100);
    quality = bound(0, quality_guess + sv_writepicture_quality.integer, 100); // assume it can do 10 failed attempts
 
    while(!(result = JPEG_try_SaveImage_to_Buffer(&cinfo, jpegbuf, jpegsize, quality, width, height, data)))
    {
        --quality;
        if(quality < 0)
        {
            Con_Printf("couldn't write image at all, probably too big\n");
            return 0;
        }
    }
    qjpeg_destroy_compress (&cinfo);
    Con_DPrintf("JPEG_SaveImage_to_Buffer: guessed quality/size %d/%d, actually got %d/%d\n", quality_guess, (int)jpegsize, quality, (int)result);
 
    return result;
 
error_caught:
    qjpeg_destroy_compress (&cinfo);
    return 0;
}
 
typedef struct CompressedImageCacheItem
{
    char imagename[MAX_QPATH];
    size_t maxsize;
    void *compressed;
    size_t compressed_size;
    struct CompressedImageCacheItem *next;
}
CompressedImageCacheItem;
#define COMPRESSEDIMAGECACHE_SIZE 4096
static CompressedImageCacheItem *CompressedImageCache[COMPRESSEDIMAGECACHE_SIZE];
 
static void CompressedImageCache_Add(const char *imagename, size_t maxsize, void *compressed, size_t compressed_size)
{
    char vabuf[1024];
    const char *hashkey = va(vabuf, sizeof(vabuf), "%s:%d", imagename, (int) maxsize);
    int hashindex = CRC_Block((unsigned char *) hashkey, strlen(hashkey)) % COMPRESSEDIMAGECACHE_SIZE;
    CompressedImageCacheItem *i;
 
    if(strlen(imagename) >= MAX_QPATH)
        return; // can't add this
 
    i = (CompressedImageCacheItem*) Z_Malloc(sizeof(CompressedImageCacheItem));
    dp_strlcpy(i->imagename, imagename, sizeof(i->imagename));
    i->maxsize = maxsize;
    i->compressed = compressed;
    i->compressed_size = compressed_size;
    i->next = CompressedImageCache[hashindex];
    CompressedImageCache[hashindex] = i;
}
 
static CompressedImageCacheItem *CompressedImageCache_Find(const char *imagename, size_t maxsize)
{
    char vabuf[1024];
    const char *hashkey = va(vabuf, sizeof(vabuf), "%s:%d", imagename, (int) maxsize);
    int hashindex = CRC_Block((unsigned char *) hashkey, strlen(hashkey)) % COMPRESSEDIMAGECACHE_SIZE;
    CompressedImageCacheItem *i = CompressedImageCache[hashindex];
 
    while(i)
    {
        if(i->maxsize == maxsize)
            if(!strcmp(i->imagename, imagename))
                return i;
        i = i->next;
    }
    return NULL;
}
 
qbool Image_Compress(const char *imagename, size_t maxsize, void **buf, size_t *size)
{
    unsigned char *imagedata, *newimagedata;
    int maxPixelCount;
    int components[3] = {2, 1, 0};
    CompressedImageCacheItem *i;
 
    JPEG_OpenLibrary (); // for now; LH had the idea of replacing this by a better format
    PNG_OpenLibrary (); // for loading
 
    // No DLL = no JPEGs
    if (!jpeg_dll)
    {
        Con_Print("You need the libjpeg library to save JPEG images\n");
        return false;
    }
 
    i = CompressedImageCache_Find(imagename, maxsize);
    if(i)
    {
        *size = i->compressed_size;
        *buf = i->compressed;
        return (*buf != NULL);
    }
 
    // load the image
    imagedata = loadimagepixelsbgra(imagename, true, false, false, NULL);
    if(!imagedata)
        return false;
 
    // find an appropriate size for somewhat okay compression
    if(maxsize <= 768)
        maxPixelCount = 32 * 32;
    else if(maxsize <= 1024)
        maxPixelCount = 64 * 64;
    else if(maxsize <= 4096)
        maxPixelCount = 128 * 128;
    else
        maxPixelCount = 256 * 256;
 
    while(image_width * image_height > maxPixelCount)
    {
        int one = 1;
        Image_MipReduce32(imagedata, imagedata, &image_width, &image_height, &one, image_width/2, image_height/2, 1);
    }
 
    newimagedata = (unsigned char *) Mem_Alloc(tempmempool, image_width * image_height * 3);
 
    // convert the image from BGRA to RGB
    Image_CopyMux(newimagedata, imagedata, image_width, image_height, false, false, false, 3, 4, components);
    Mem_Free(imagedata);
 
    // try to compress it to JPEG
    *buf = Z_Malloc(maxsize);
    *size = JPEG_SaveImage_to_Buffer((char *) *buf, maxsize, image_width, image_height, newimagedata);
    Mem_Free(newimagedata);
 
    if(!*size)
    {
        Z_Free(*buf);
        *buf = NULL;
        Con_Printf("could not compress image %s to %d bytes\n", imagename, (int)maxsize);
        // return false;
        // also cache failures!
    }
 
    // store it in the cache
    CompressedImageCache_Add(imagename, maxsize, *buf, *size);
    return (*buf != NULL);
}