/* * jdapi.c * * Copyright (C) 1994, Thomas G. Lane. * This file is part of the Independent JPEG Group's software. * For conditions of distribution and use, see the accompanying README file. * * This file contains application interface code for the decompression half of * the JPEG library.  Most of the routines intended to be called directly by * an application are in this file.  But also see jcomapi.c for routines * shared by compression and decompression. */#include "jinclude.h"#include "jpegint.h"/* * Initialization of a JPEG decompression object. * The error manager must already be set up (in case memory manager fails). */GLOBAL voidjpeg_create_decompress (j_decompress_ptr cinfo){  int i;  /* For debugging purposes, zero the whole master structure.   * But error manager pointer is already there, so save and restore it.   */  {    struct jpeg_error_mgr * err = cinfo->err;    MEMZERO(cinfo, SIZEOF(struct jpeg_decompress_struct));    cinfo->err = err;  }  cinfo->is_decompressor = TRUE;  /* Initialize a memory manager instance for this object */  jinit_memory_mgr((j_common_ptr) cinfo);  /* Zero out pointers to permanent structures. */  cinfo->progress = NULL;  cinfo->src = NULL;  for (i = 0; i < NUM_QUANT_TBLS; i++)    cinfo->quant_tbl_ptrs[i] = NULL;  for (i = 0; i < NUM_HUFF_TBLS; i++) {    cinfo->dc_huff_tbl_ptrs[i] = NULL;    cinfo->ac_huff_tbl_ptrs[i] = NULL;  }  cinfo->sample_range_limit = NULL;  /* Initialize marker processor so application can override methods   * for COM, APPn markers before calling jpeg_read_header.   */  cinfo->marker = NULL;  jinit_marker_reader(cinfo);  /* OK, I'm ready */  cinfo->global_state = DSTATE_START;}/* * Destruction of a JPEG decompression object */GLOBAL voidjpeg_destroy_decompress (j_decompress_ptr cinfo){  jpeg_destroy((j_common_ptr) cinfo); /* use common routine */}/* * Set default decompression parameters. */LOCAL voiddefault_decompress_parms (j_decompress_ptr cinfo){  /* Guess the input colorspace, and set output colorspace accordingly. */  /* (Wish JPEG committee had provided a real way to specify this...) */  /* Note application may override our guesses. */  cinfo->want_raw_output = FALSE;  switch (cinfo->num_components) {  case 1:    cinfo->jpeg_color_space = JCS_GRAYSCALE;    cinfo->out_color_space = JCS_GRAYSCALE;    break;      case 3:    if (cinfo->saw_JFIF_marker) {      cinfo->jpeg_color_space = JCS_YCbCr; /* JFIF implies YCbCr */    } else if (cinfo->saw_Adobe_marker) {      switch (cinfo->Adobe_transform) {      case 0:	cinfo->jpeg_color_space = JCS_RGB;	break;      case 1:	cinfo->jpeg_color_space = JCS_YCbCr;	break;      default:	WARNMS1(cinfo, JWRN_ADOBE_XFORM, cinfo->Adobe_transform);	cinfo->jpeg_color_space = JCS_YCbCr; /* assume it's YCbCr */	break;      }    } else {      /* Saw no special markers, try to guess from the component IDs */      int cid0 = cinfo->comp_info[0].component_id;      int cid1 = cinfo->comp_info[1].component_id;      int cid2 = cinfo->comp_info[2].component_id;      if (cid0 == 1 && cid1 == 2 && cid2 == 3)	cinfo->jpeg_color_space = JCS_YCbCr; /* assume JFIF w/out marker */      else if (cid0 == 82 && cid1 == 71 && cid2 == 66)	cinfo->jpeg_color_space = JCS_RGB; /* ASCII 'R', 'G', 'B' */      else {	TRACEMS3(cinfo, 1, JTRC_UNKNOWN_IDS, cid0, cid1, cid2);	cinfo->jpeg_color_space = JCS_YCbCr; /* assume it's YCbCr */      }    }    /* Always guess RGB is proper output colorspace. */    cinfo->out_color_space = JCS_RGB;    break;      case 4:    if (cinfo->saw_Adobe_marker) {      switch (cinfo->Adobe_transform) {      case 0:	cinfo->jpeg_color_space = JCS_CMYK;	break;      case 2:	cinfo->jpeg_color_space = JCS_YCCK;	break;      default:	WARNMS1(cinfo, JWRN_ADOBE_XFORM, cinfo->Adobe_transform);	cinfo->jpeg_color_space = JCS_YCCK; /* assume it's YCCK */	break;      }    } else {      /* No special markers, assume straight CMYK. */      cinfo->jpeg_color_space = JCS_CMYK;    }    cinfo->out_color_space = JCS_CMYK;    break;      default:    cinfo->jpeg_color_space = JCS_UNKNOWN;    cinfo->out_color_space = JCS_UNKNOWN;    break;  }  /* Set defaults for other decompression parameters. */  cinfo->scale_num = 1;		/* 1:1 scaling */  cinfo->scale_denom = 1;  cinfo->output_gamma = 1.0;  cinfo->quantize_colors = FALSE;  /* We set these in case application only sets quantize_colors. */  cinfo->two_pass_quantize = TRUE;  cinfo->use_dithering = TRUE;  cinfo->desired_number_of_colors = 256;  cinfo->do_block_smoothing = FALSE;  cinfo->do_fancy_upsampling = TRUE;  cinfo->colormap = NULL;}/* * Decompression startup: read start of JPEG datastream to see what's there. * Need only initialize JPEG object and supply a data source before calling. * * This routine will read as far as the first SOS marker (ie, actual start of * compressed data), and will save all tables and parameters in the JPEG * object.  It will also initialize the decompression parameters to default * values, and finally return JPEG_HEADER_OK.  On return, the application may * adjust the decompression parameters and then call jpeg_start_decompress. * (Or, if the application only wanted to determine the image parameters, * the data need not be decompressed.  In that case, call jpeg_abort or * jpeg_destroy to release any temporary space.) * If an abbreviated (tables only) datastream is presented, the routine will * return JPEG_HEADER_TABLES_ONLY upon reaching EOI.  The application may then * re-use the JPEG object to read the abbreviated image datastream(s). * It is unnecessary (but OK) to call jpeg_abort in this case. * The JPEG_SUSPENDED return code only occurs if the data source module * requests suspension of the decompressor.  In this case the application * should load more source data and then re-call jpeg_read_header to resume * processing. * If a non-suspending data source is used and require_image is TRUE, then the * return code need not be inspected since only JPEG_HEADER_OK is possible. */GLOBAL intjpeg_read_header (j_decompress_ptr cinfo, boolean require_image){  int retcode;  if (cinfo->global_state == DSTATE_START) {    /* First-time actions: reset appropriate modules */    (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);    (*cinfo->marker->reset_marker_reader) (cinfo);    (*cinfo->src->init_source) (cinfo);    cinfo->global_state = DSTATE_INHEADER;  } else if (cinfo->global_state != DSTATE_INHEADER) {    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);  }  retcode = (*cinfo->marker->read_markers) (cinfo);  switch (retcode) {  case JPEG_HEADER_OK:		/* Found SOS, prepare to decompress */    /* Set up default parameters based on header data */    default_decompress_parms(cinfo);    /* Set global state: ready for start_decompress */    cinfo->global_state = DSTATE_READY;    break;  case JPEG_HEADER_TABLES_ONLY:	/* Found EOI before any SOS */    if (cinfo->marker->saw_SOF)      ERREXIT(cinfo, JERR_SOF_NO_SOS);    if (require_image)		/* Complain if application wants an image */      ERREXIT(cinfo, JERR_NO_IMAGE);    /* We need not do any cleanup since only permanent storage (for DQT, DHT)     * has been allocated.     */    /* Set global state: ready for a new datastream */    cinfo->global_state = DSTATE_START;    break;  case JPEG_SUSPENDED:		/* Had to suspend before end of headers */    /* no work */    break;  }  return retcode;}/* * Decompression initialization. * jpeg_read_header must be completed before calling this. * * If a multipass operating mode was selected, this will do all but the * last pass, and thus may take a great deal of time. */GLOBAL voidjpeg_start_decompress (j_decompress_ptr cinfo){  if (cinfo->global_state != DSTATE_READY)    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);  /* Perform master selection of active modules */  jinit_master_decompress(cinfo);  /* Do all but the final (output) pass, and set up for that one. */  for (;;) {    (*cinfo->master->prepare_for_pass) (cinfo);    if (cinfo->master->is_last_pass)      break;    /* Drive pass here??? */    /* Terminate pass here??? */  }  /* Ready for application to drive last pass through jpeg_read_scanlines */  cinfo->output_scanline = 0;  cinfo->global_state = DSTATE_SCANNING;}/* * Read some scanlines of data from the JPEG decompressor. * * The return value will be the number of lines actually read. * This may be less than the number requested in several cases, * including bottom of image, data source suspension, and operating * modes that emit multiple scanlines at a time. */GLOBAL JDIMENSIONjpeg_read_scanlines (j_decompress_ptr cinfo, JSAMPARRAY scanlines,		     JDIMENSION max_lines){  JDIMENSION row_ctr;  if (cinfo->global_state != DSTATE_SCANNING)    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);  row_ctr = 0;  (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines);  cinfo->output_scanline += row_ctr;  return row_ctr;}GLOBAL JDIMENSIONjpeg_read_raw_scanlines(j_decompress_ptr cinfo, JSAMPIMAGE scanarray,                         JDIMENSION max_lines){ JDIMENSION row_ctr; if (cinfo->global_state != DSTATE_SCANNING)   ERREXIT1(cinfo,JERR_BAD_STATE,cinfo->global_state); row_ctr =0; (*cinfo->main->process_data)(cinfo,scanarray,&row_ctr,max_lines);   cinfo->output_scanline += row_ctr; return row_ctr;}/* * Finish JPEG decompression. * * This will normally just verify the file trailer and release temp storage. * * Returns FALSE if suspended.  The return value need be inspected only if * a suspending data source is used. */GLOBAL booleanjpeg_finish_decompress (j_decompress_ptr cinfo){  if (cinfo->global_state == DSTATE_SCANNING &&      cinfo->output_scanline == cinfo->output_height) {    /* Terminate final pass */    (*cinfo->main->finish_pass) (cinfo);    cinfo->global_state = DSTATE_STOPPING;  } else if (cinfo->global_state != DSTATE_STOPPING) {    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);  }  /* Check for EOI in source file */  switch ((*cinfo->marker->read_markers) (cinfo)) {  case JPEG_HEADER_OK:		/* Found SOS!? */    ERREXIT(cinfo, JERR_EOI_EXPECTED);    break;  case JPEG_HEADER_TABLES_ONLY:	/* Found EOI, A-OK */    break;  case JPEG_SUSPENDED:		/* Suspend, come back later */    return FALSE;  }  /* Do final cleanup ??? */  (*cinfo->src->term_source) (cinfo);  /* We can use jpeg_abort to release memory and reset global_state */  jpeg_abort((j_common_ptr) cinfo);  return TRUE;}/* * Abort processing of a JPEG decompression operation, * but don't destroy the object itself. */GLOBAL voidjpeg_abort_decompress (j_decompress_ptr cinfo){  jpeg_abort((j_common_ptr) cinfo); /* use common routine */}