vx32

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jdapistd.c (9348B)


      1 /*
      2  * jdapistd.c
      3  *
      4  * Copyright (C) 1994-1996, Thomas G. Lane.
      5  * This file is part of the Independent JPEG Group's software.
      6  * For conditions of distribution and use, see the accompanying README file.
      7  *
      8  * This file contains application interface code for the decompression half
      9  * of the JPEG library.  These are the "standard" API routines that are
     10  * used in the normal full-decompression case.  They are not used by a
     11  * transcoding-only application.  Note that if an application links in
     12  * jpeg_start_decompress, it will end up linking in the entire decompressor.
     13  * We thus must separate this file from jdapimin.c to avoid linking the
     14  * whole decompression library into a transcoder.
     15  */
     16 
     17 #define JPEG_INTERNALS
     18 #include "jinclude.h"
     19 #include "jpeglib.h"
     20 
     21 
     22 /* Forward declarations */
     23 LOCAL(boolean) output_pass_setup JPP((j_decompress_ptr cinfo));
     24 
     25 
     26 /*
     27  * Decompression initialization.
     28  * jpeg_read_header must be completed before calling this.
     29  *
     30  * If a multipass operating mode was selected, this will do all but the
     31  * last pass, and thus may take a great deal of time.
     32  *
     33  * Returns FALSE if suspended.  The return value need be inspected only if
     34  * a suspending data source is used.
     35  */
     36 
     37 GLOBAL(boolean)
     38 jpeg_start_decompress (j_decompress_ptr cinfo)
     39 {
     40   if (cinfo->global_state == DSTATE_READY) {
     41     /* First call: initialize master control, select active modules */
     42     jinit_master_decompress(cinfo);
     43     if (cinfo->buffered_image) {
     44       /* No more work here; expecting jpeg_start_output next */
     45       cinfo->global_state = DSTATE_BUFIMAGE;
     46       return TRUE;
     47     }
     48     cinfo->global_state = DSTATE_PRELOAD;
     49   }
     50   if (cinfo->global_state == DSTATE_PRELOAD) {
     51     /* If file has multiple scans, absorb them all into the coef buffer */
     52     if (cinfo->inputctl->has_multiple_scans) {
     53 #ifdef D_MULTISCAN_FILES_SUPPORTED
     54       for (;;) {
     55 	int retcode;
     56 	/* Call progress monitor hook if present */
     57 	if (cinfo->progress != NULL)
     58 	  (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
     59 	/* Absorb some more input */
     60 	retcode = (*cinfo->inputctl->consume_input) (cinfo);
     61 	if (retcode == JPEG_SUSPENDED)
     62 	  return FALSE;
     63 	if (retcode == JPEG_REACHED_EOI)
     64 	  break;
     65 	/* Advance progress counter if appropriate */
     66 	if (cinfo->progress != NULL &&
     67 	    (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
     68 	  if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
     69 	    /* jdmaster underestimated number of scans; ratchet up one scan */
     70 	    cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
     71 	  }
     72 	}
     73       }
     74 #else
     75       ERREXIT(cinfo, JERR_NOT_COMPILED);
     76 #endif /* D_MULTISCAN_FILES_SUPPORTED */
     77     }
     78     cinfo->output_scan_number = cinfo->input_scan_number;
     79   } else if (cinfo->global_state != DSTATE_PRESCAN)
     80     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
     81   /* Perform any dummy output passes, and set up for the final pass */
     82   return output_pass_setup(cinfo);
     83 }
     84 
     85 
     86 /*
     87  * Set up for an output pass, and perform any dummy pass(es) needed.
     88  * Common subroutine for jpeg_start_decompress and jpeg_start_output.
     89  * Entry: global_state = DSTATE_PRESCAN only if previously suspended.
     90  * Exit: If done, returns TRUE and sets global_state for proper output mode.
     91  *       If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN.
     92  */
     93 
     94 LOCAL(boolean)
     95 output_pass_setup (j_decompress_ptr cinfo)
     96 {
     97   if (cinfo->global_state != DSTATE_PRESCAN) {
     98     /* First call: do pass setup */
     99     (*cinfo->master->prepare_for_output_pass) (cinfo);
    100     cinfo->output_scanline = 0;
    101     cinfo->global_state = DSTATE_PRESCAN;
    102   }
    103   /* Loop over any required dummy passes */
    104   while (cinfo->master->is_dummy_pass) {
    105 #ifdef QUANT_2PASS_SUPPORTED
    106     /* Crank through the dummy pass */
    107     while (cinfo->output_scanline < cinfo->output_height) {
    108       JDIMENSION last_scanline;
    109       /* Call progress monitor hook if present */
    110       if (cinfo->progress != NULL) {
    111 	cinfo->progress->pass_counter = (long) cinfo->output_scanline;
    112 	cinfo->progress->pass_limit = (long) cinfo->output_height;
    113 	(*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
    114       }
    115       /* Process some data */
    116       last_scanline = cinfo->output_scanline;
    117       (*cinfo->main->process_data) (cinfo, (JSAMPARRAY) NULL,
    118 				    &cinfo->output_scanline, (JDIMENSION) 0);
    119       if (cinfo->output_scanline == last_scanline)
    120 	return FALSE;		/* No progress made, must suspend */
    121     }
    122     /* Finish up dummy pass, and set up for another one */
    123     (*cinfo->master->finish_output_pass) (cinfo);
    124     (*cinfo->master->prepare_for_output_pass) (cinfo);
    125     cinfo->output_scanline = 0;
    126 #else
    127     ERREXIT(cinfo, JERR_NOT_COMPILED);
    128 #endif /* QUANT_2PASS_SUPPORTED */
    129   }
    130   /* Ready for application to drive output pass through
    131    * jpeg_read_scanlines or jpeg_read_raw_data.
    132    */
    133   cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING;
    134   return TRUE;
    135 }
    136 
    137 
    138 /*
    139  * Read some scanlines of data from the JPEG decompressor.
    140  *
    141  * The return value will be the number of lines actually read.
    142  * This may be less than the number requested in several cases,
    143  * including bottom of image, data source suspension, and operating
    144  * modes that emit multiple scanlines at a time.
    145  *
    146  * Note: we warn about excess calls to jpeg_read_scanlines() since
    147  * this likely signals an application programmer error.  However,
    148  * an oversize buffer (max_lines > scanlines remaining) is not an error.
    149  */
    150 
    151 GLOBAL(JDIMENSION)
    152 jpeg_read_scanlines (j_decompress_ptr cinfo, JSAMPARRAY scanlines,
    153 		     JDIMENSION max_lines)
    154 {
    155   JDIMENSION row_ctr;
    156 
    157   if (cinfo->global_state != DSTATE_SCANNING)
    158     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
    159   if (cinfo->output_scanline >= cinfo->output_height) {
    160     WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
    161     return 0;
    162   }
    163 
    164   /* Call progress monitor hook if present */
    165   if (cinfo->progress != NULL) {
    166     cinfo->progress->pass_counter = (long) cinfo->output_scanline;
    167     cinfo->progress->pass_limit = (long) cinfo->output_height;
    168     (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
    169   }
    170 
    171   /* Process some data */
    172   row_ctr = 0;
    173   (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines);
    174   cinfo->output_scanline += row_ctr;
    175   return row_ctr;
    176 }
    177 
    178 
    179 /*
    180  * Alternate entry point to read raw data.
    181  * Processes exactly one iMCU row per call, unless suspended.
    182  */
    183 
    184 GLOBAL(JDIMENSION)
    185 jpeg_read_raw_data (j_decompress_ptr cinfo, JSAMPIMAGE data,
    186 		    JDIMENSION max_lines)
    187 {
    188   JDIMENSION lines_per_iMCU_row;
    189 
    190   if (cinfo->global_state != DSTATE_RAW_OK)
    191     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
    192   if (cinfo->output_scanline >= cinfo->output_height) {
    193     WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
    194     return 0;
    195   }
    196 
    197   /* Call progress monitor hook if present */
    198   if (cinfo->progress != NULL) {
    199     cinfo->progress->pass_counter = (long) cinfo->output_scanline;
    200     cinfo->progress->pass_limit = (long) cinfo->output_height;
    201     (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
    202   }
    203 
    204   /* Verify that at least one iMCU row can be returned. */
    205   lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size;
    206   if (max_lines < lines_per_iMCU_row)
    207     ERREXIT(cinfo, JERR_BUFFER_SIZE);
    208 
    209   /* Decompress directly into user's buffer. */
    210   if (! (*cinfo->coef->decompress_data) (cinfo, data))
    211     return 0;			/* suspension forced, can do nothing more */
    212 
    213   /* OK, we processed one iMCU row. */
    214   cinfo->output_scanline += lines_per_iMCU_row;
    215   return lines_per_iMCU_row;
    216 }
    217 
    218 
    219 /* Additional entry points for buffered-image mode. */
    220 
    221 #ifdef D_MULTISCAN_FILES_SUPPORTED
    222 
    223 /*
    224  * Initialize for an output pass in buffered-image mode.
    225  */
    226 
    227 GLOBAL(boolean)
    228 jpeg_start_output (j_decompress_ptr cinfo, int scan_number)
    229 {
    230   if (cinfo->global_state != DSTATE_BUFIMAGE &&
    231       cinfo->global_state != DSTATE_PRESCAN)
    232     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
    233   /* Limit scan number to valid range */
    234   if (scan_number <= 0)
    235     scan_number = 1;
    236   if (cinfo->inputctl->eoi_reached &&
    237       scan_number > cinfo->input_scan_number)
    238     scan_number = cinfo->input_scan_number;
    239   cinfo->output_scan_number = scan_number;
    240   /* Perform any dummy output passes, and set up for the real pass */
    241   return output_pass_setup(cinfo);
    242 }
    243 
    244 
    245 /*
    246  * Finish up after an output pass in buffered-image mode.
    247  *
    248  * Returns FALSE if suspended.  The return value need be inspected only if
    249  * a suspending data source is used.
    250  */
    251 
    252 GLOBAL(boolean)
    253 jpeg_finish_output (j_decompress_ptr cinfo)
    254 {
    255   if ((cinfo->global_state == DSTATE_SCANNING ||
    256        cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) {
    257     /* Terminate this pass. */
    258     /* We do not require the whole pass to have been completed. */
    259     (*cinfo->master->finish_output_pass) (cinfo);
    260     cinfo->global_state = DSTATE_BUFPOST;
    261   } else if (cinfo->global_state != DSTATE_BUFPOST) {
    262     /* BUFPOST = repeat call after a suspension, anything else is error */
    263     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
    264   }
    265   /* Read markers looking for SOS or EOI */
    266   while (cinfo->input_scan_number <= cinfo->output_scan_number &&
    267 	 ! cinfo->inputctl->eoi_reached) {
    268     if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
    269       return FALSE;		/* Suspend, come back later */
    270   }
    271   cinfo->global_state = DSTATE_BUFIMAGE;
    272   return TRUE;
    273 }
    274 
    275 #endif /* D_MULTISCAN_FILES_SUPPORTED */