jdmarker.c

Jpeg source code,jpeg编码解码示范

/*
 * jdmarker.c
 *
 * Copyright (C) 1991-1996, 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 routines to decode JPEG datastream markers.
 * Most of the complexity arises from our desire to support input
 * suspension: if not all of the data for a marker is available,
 * we must exit back to the application.  On resumption, we reprocess
 * the marker.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


typedef enum {			/* JPEG marker codes */
  M_SOF0  = 0xc0,
  M_SOF1  = 0xc1,
  M_SOF2  = 0xc2,
  M_SOF3  = 0xc3,
  
  M_SOF5  = 0xc5,
  M_SOF6  = 0xc6,
  M_SOF7  = 0xc7,
  
  M_JPG   = 0xc8,
  M_SOF9  = 0xc9,
  M_SOF10 = 0xca,
  M_SOF11 = 0xcb,
  
  M_SOF13 = 0xcd,
  M_SOF14 = 0xce,
  M_SOF15 = 0xcf,
  
  M_DHT   = 0xc4,
  
  M_DAC   = 0xcc,
  
  M_RST0  = 0xd0,
  M_RST1  = 0xd1,
  M_RST2  = 0xd2,
  M_RST3  = 0xd3,
  M_RST4  = 0xd4,
  M_RST5  = 0xd5,
  M_RST6  = 0xd6,
  M_RST7  = 0xd7,
  
  M_SOI   = 0xd8,
  M_EOI   = 0xd9,
  M_SOS   = 0xda,
  M_DQT   = 0xdb,
  M_DNL   = 0xdc,
  M_DRI   = 0xdd,
  M_DHP   = 0xde,
  M_EXP   = 0xdf,
  
  M_APP0  = 0xe0,
  M_APP1  = 0xe1,
  M_APP2  = 0xe2,
  M_APP3  = 0xe3,
  M_APP4  = 0xe4,
  M_APP5  = 0xe5,
  M_APP6  = 0xe6,
  M_APP7  = 0xe7,
  M_APP8  = 0xe8,
  M_APP9  = 0xe9,
  M_APP10 = 0xea,
  M_APP11 = 0xeb,
  M_APP12 = 0xec,
  M_APP13 = 0xed,
  M_APP14 = 0xee,
  M_APP15 = 0xef,
  
  M_JPG0  = 0xf0,
  M_JPG13 = 0xfd,
  M_COM   = 0xfe,
  
  M_TEM   = 0x01,
  
  M_ERROR = 0x100
} JPEG_MARKER;


/*
 * Macros for fetching data from the data source module.
 *
 * At all times, cinfo->src->next_input_byte and ->bytes_in_buffer reflect
 * the current restart point; we update them only when we have reached a
 * suitable place to restart if a suspension occurs.
 */

/* Declare and initialize local copies of input pointer/count */
#define INPUT_VARS(cinfo)  \
	struct jpeg_source_mgr * datasrc = (cinfo)->src;  \
	const JOCTET * next_input_byte = datasrc->next_input_byte;  \
	size_t bytes_in_buffer = datasrc->bytes_in_buffer

/* Unload the local copies --- do this only at a restart boundary */
#define INPUT_SYNC(cinfo)  \
	( datasrc->next_input_byte = next_input_byte,  \
	  datasrc->bytes_in_buffer = bytes_in_buffer )

/* Reload the local copies --- seldom used except in MAKE_BYTE_AVAIL */
#define INPUT_RELOAD(cinfo)  \
	( next_input_byte = datasrc->next_input_byte,  \
	  bytes_in_buffer = datasrc->bytes_in_buffer )

/* Internal macro for INPUT_BYTE and INPUT_2BYTES: make a byte available.
 * Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
 * but we must reload the local copies after a successful fill.
 */
#define MAKE_BYTE_AVAIL(cinfo,action)  \
	if (bytes_in_buffer == 0) {  \
	  if (! (*datasrc->fill_input_buffer) (cinfo))  \
	    { action; }  \
	  INPUT_RELOAD(cinfo);  \
	}  \
	bytes_in_buffer--

/* Read a byte into variable V.
 * If must suspend, take the specified action (typically "return FALSE").
 */
#define INPUT_BYTE(cinfo,V,action)  \
	MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
		  V = GETJOCTET(*next_input_byte++); )

/* As above, but read two bytes interpreted as an unsigned 16-bit integer.
 * V should be declared unsigned int or perhaps INT32.
 */
#define INPUT_2BYTES(cinfo,V,action)  \
	MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
		  V = ((unsigned int) GETJOCTET(*next_input_byte++)) << 8; \
		  MAKE_BYTE_AVAIL(cinfo,action); \
		  V += GETJOCTET(*next_input_byte++); )


/*
 * Routines to process JPEG markers.
 *
 * Entry condition: JPEG marker itself has been read and its code saved
 *   in cinfo->unread_marker; input restart point is just after the marker.
 *
 * Exit: if return TRUE, have read and processed any parameters, and have
 *   updated the restart point to point after the parameters.
 *   If return FALSE, was forced to suspend before reaching end of
 *   marker parameters; restart point has not been moved.  Same routine
 *   will be called again after application supplies more input data.
 *
 * This approach to suspension assumes that all of a marker's parameters can
 * fit into a single input bufferload.  This should hold for "normal"
 * markers.  Some COM/APPn markers might have large parameter segments,
 * but we use skip_input_data to get past those, and thereby put the problem
 * on the source manager's shoulders.
 *
 * Note that we don't bother to avoid duplicate trace messages if a
 * suspension occurs within marker parameters.  Other side effects
 * require more care.
 */


LOCAL(boolean)
get_soi (j_decompress_ptr cinfo)
/* Process an SOI marker */
{
  int i;
  
  TRACEMS(cinfo, 1, JTRC_SOI);

  if (cinfo->marker->saw_SOI)
    ERREXIT(cinfo, JERR_SOI_DUPLICATE);

  /* Reset all parameters that are defined to be reset by SOI */

  for (i = 0; i < NUM_ARITH_TBLS; i++) {
    cinfo->arith_dc_L[i] = 0;
    cinfo->arith_dc_U[i] = 1;
    cinfo->arith_ac_K[i] = 5;
  }
  cinfo->restart_interval = 0;

  /* Set initial assumptions for colorspace etc */

  cinfo->jpeg_color_space = JCS_UNKNOWN;
  cinfo->CCIR601_sampling = FALSE; /* Assume non-CCIR sampling??? */

  cinfo->saw_JFIF_marker = FALSE;
  cinfo->density_unit = 0;	/* set default JFIF APP0 values */
  cinfo->X_density = 1;
  cinfo->Y_density = 1;
  cinfo->saw_Adobe_marker = FALSE;
  cinfo->Adobe_transform = 0;

  cinfo->marker->saw_SOI = TRUE;

  return TRUE;
}


LOCAL(boolean)
get_sof (j_decompress_ptr cinfo, boolean is_prog, boolean is_arith)
/* Process a SOFn marker */
{
  INT32 length;
  int c, ci;
  jpeg_component_info * compptr;
  INPUT_VARS(cinfo);

  cinfo->progressive_mode = is_prog;
  cinfo->arith_code = is_arith;

  INPUT_2BYTES(cinfo, length, return FALSE);

  INPUT_BYTE(cinfo, cinfo->data_precision, return FALSE);
  INPUT_2BYTES(cinfo, cinfo->image_height, return FALSE);
  INPUT_2BYTES(cinfo, cinfo->image_width, return FALSE);
  INPUT_BYTE(cinfo, cinfo->num_components, return FALSE);

  length -= 8;

  TRACEMS4(cinfo, 1, JTRC_SOF, cinfo->unread_marker,
	   (int) cinfo->image_width, (int) cinfo->image_height,
	   cinfo->num_components);

  if (cinfo->marker->saw_SOF)
    ERREXIT(cinfo, JERR_SOF_DUPLICATE);

  /* We don't support files in which the image height is initially specified */
  /* as 0 and is later redefined by DNL.  As long as we have to check that,  */
  /* might as well have a general sanity check. */
  if (cinfo->image_height <= 0 || cinfo->image_width <= 0
      || cinfo->num_components <= 0)
    ERREXIT(cinfo, JERR_EMPTY_IMAGE);

  if (length != (cinfo->num_components * 3))
    ERREXIT(cinfo, JERR_BAD_LENGTH);

  if (cinfo->comp_info == NULL)	/* do only once, even if suspend */
    cinfo->comp_info = (jpeg_component_info *) (*cinfo->mem->alloc_small)
			((j_common_ptr) cinfo, JPOOL_IMAGE,
			 cinfo->num_components * SIZEOF(jpeg_component_info));
  
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    compptr->component_index = ci;
    INPUT_BYTE(cinfo, compptr->component_id, return FALSE);
    INPUT_BYTE(cinfo, c, return FALSE);
    compptr->h_samp_factor = (c >> 4) & 15;
    compptr->v_samp_factor = (c     ) & 15;
    INPUT_BYTE(cinfo, compptr->quant_tbl_no, return FALSE);

    TRACEMS4(cinfo, 1, JTRC_SOF_COMPONENT,
	     compptr->component_id, compptr->h_samp_factor,
	     compptr->v_samp_factor, compptr->quant_tbl_no);
  }

  cinfo->marker->saw_SOF = TRUE;

  INPUT_SYNC(cinfo);
  return TRUE;
}


LOCAL(boolean)
get_sos (j_decompress_ptr cinfo)
/* Process a SOS marker */
{
  INT32 length;
  int i, ci, n, c, cc;
  jpeg_component_info * compptr;
  INPUT_VARS(cinfo);

  if (! cinfo->marker->saw_SOF)
    ERREXIT(cinfo, JERR_SOS_NO_SOF);

  INPUT_2BYTES(cinfo, length, return FALSE);

  INPUT_BYTE(cinfo, n, return FALSE); /* Number of components */

  if (length != (n * 2 + 6) || n < 1 || n > MAX_COMPS_IN_SCAN)
    ERREXIT(cinfo, JERR_BAD_LENGTH);

  TRACEMS1(cinfo, 1, JTRC_SOS, n);

  cinfo->comps_in_scan = n;

  /* Collect the component-spec parameters */

  for (i = 0; i < n; i++) {
    INPUT_BYTE(cinfo, cc, return FALSE);
    INPUT_BYTE(cinfo, c, return FALSE);
    
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	 ci++, compptr++) {
      if (cc == compptr->component_id)
	goto id_found;
    }

    ERREXIT1(cinfo, JERR_BAD_COMPONENT_ID, cc);

  id_found:

    cinfo->cur_comp_info[i] = compptr;
    compptr->dc_tbl_no = (c >> 4) & 15;
    compptr->ac_tbl_no = (c     ) & 15;
    
    TRACEMS3(cinfo, 1, JTRC_SOS_COMPONENT, cc,
	     compptr->dc_tbl_no, compptr->ac_tbl_no);
  }

  /* Collect the additional scan parameters Ss, Se, Ah/Al. */
  INPUT_BYTE(cinfo, c, return FALSE);
  cinfo->Ss = c;
  INPUT_BYTE(cinfo, c, return FALSE);
  cinfo->Se = c;
  INPUT_BYTE(cinfo, c, return FALSE);
  cinfo->Ah = (c >> 4) & 15;
  cinfo->Al = (c     ) & 15;

  TRACEMS4(cinfo, 1, JTRC_SOS_PARAMS, cinfo->Ss, cinfo->Se,
	   cinfo->Ah, cinfo->Al);

  /* Prepare to scan data & restart markers */
  cinfo->marker->next_restart_num = 0;

  /* Count another SOS marker */
  cinfo->input_scan_number++;

  INPUT_SYNC(cinfo);
  return TRUE;
}


METHODDEF(boolean)
get_app0 (j_decompress_ptr cinfo)
/* Process an APP0 marker */
{
#define JFIF_LEN 14
  INT32 length;
  UINT8 b[JFIF_LEN];
  int buffp;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  length -= 2;

  /* See if a JFIF APP0 marker is present */

  if (length >= JFIF_LEN) {