compiler/libjpeg/main/jdtrans.c

   1 /*
   2     $Id$
   3 */
   4
   5 /*
   6  * jdtrans.c
   7  *
   8  * Copyright (C) 1995-1998, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This file contains library routines for transcoding decompression,
  13  * that is, reading raw DCT coefficient arrays from an input JPEG file.
  14  * The routines in jdapimin.c will also be needed by a transcoder.
  15  */
  16
  17 #define JPEG_INTERNALS
  18 #include "jinclude.h"
  19 #include "jpeglib.h"
  20 #include "jlossy.h"
  21
  22
  23 /* Forward declarations */
  24 LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));
  25
  26
  27 /*
  28  * Read the coefficient arrays from a JPEG file.
  29  * jpeg_read_header must be completed before calling this.
  30  *
  31  * The entire image is read into a set of virtual coefficient-block arrays,
  32  * one per component.  The return value is a pointer to the array of
  33  * virtual-array descriptors.  These can be manipulated directly via the
  34  * JPEG memory manager, or handed off to jpeg_write_coefficients().
  35  * To release the memory occupied by the virtual arrays, call
  36  * jpeg_finish_decompress() when done with the data.
  37  *
  38  * An alternative usage is to simply obtain access to the coefficient arrays
  39  * during a buffered-image-mode decompression operation.  This is allowed
  40  * after any jpeg_finish_output() call.  The arrays can be accessed until
  41  * jpeg_finish_decompress() is called.  (Note that any call to the library
  42  * may reposition the arrays, so don't rely on access_virt_barray() results
  43  * to stay valid across library calls.)
  44  *
  45  * Returns NULL if suspended.  This case need be checked only if
  46  * a suspending data source is used.
  47  */
  48
  49 JGLOBAL(jvirt_barray_ptr *)
  50 jpeg_read_coefficients (j_decompress_ptr cinfo)
  51 {
  52   j_lossy_d_ptr decomp;
  53
  54   /* Can't read coefficients from lossless streams */
  55   if (cinfo->process == JPROC_LOSSLESS) {
  56     ERREXIT(cinfo, JERR_CANT_TRANSCODE);
  57     return NULL;
  58   }
  59
  60   if (cinfo->global_state == DSTATE_READY) {
  61     /* First call: initialize active modules */
  62     transdecode_master_selection(cinfo);
  63     cinfo->global_state = DSTATE_RDCOEFS;
  64   }
  65   if (cinfo->global_state == DSTATE_RDCOEFS) {
  66     /* Absorb whole file into the coef buffer */
  67     for (;;) {
  68       int retcode;
  69       /* Call progress monitor hook if present */
  70       if (cinfo->progress != NULL)
  71         (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
  72       /* Absorb some more input */
  73       retcode = (*cinfo->inputctl->consume_input) (cinfo);
  74       if (retcode == JPEG_SUSPENDED)
  75         return NULL;
  76       if (retcode == JPEG_REACHED_EOI)
  77         break;
  78       /* Advance progress counter if appropriate */
  79       if (cinfo->progress != NULL &&
  80           (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
  81         if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
  82           /* startup underestimated number of scans; ratchet up one scan */
  83           cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
  84         }
  85       }
  86     }
  87     /* Set state so that jpeg_finish_decompress does the right thing */
  88     cinfo->global_state = DSTATE_STOPPING;
  89   }
  90   /* At this point we should be in state DSTATE_STOPPING if being used
  91    * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
  92    * to the coefficients during a full buffered-image-mode decompression.
  93    */
  94   if ((cinfo->global_state == DSTATE_STOPPING ||
  95        cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
  96     return ((j_lossy_d_ptr) cinfo->codec)->coef_arrays;
  97   }
  98   /* Oops, improper usage */
  99   ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
 100   return NULL;                  /* keep compiler happy */
 101 }
 102
 103
 104 /*
 105  * Master selection of decompression modules for transcoding.
 106  * This substitutes for jdmaster.c's initialization of the full decompressor.
 107  */
 108
 109 LOCAL(void)
 110 transdecode_master_selection (j_decompress_ptr cinfo)
 111 {
 112   /* This is effectively a buffered-image operation. */
 113   cinfo->buffered_image = TRUE;
 114
 115   /* Initialize decompression codec */
 116   jinit_d_codec(cinfo);
 117
 118   /* We can now tell the memory manager to allocate virtual arrays. */
 119   (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
 120
 121   /* Initialize input side of decompressor to consume first scan. */
 122   (*cinfo->inputctl->start_input_pass) (cinfo);
 123
 124   /* Initialize progress monitoring. */
 125   if (cinfo->progress != NULL) {
 126     int nscans;
 127     /* Estimate number of scans to set pass_limit. */
 128     if (cinfo->process == JPROC_PROGRESSIVE) {
 129       /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
 130       nscans = 2 + 3 * cinfo->num_components;
 131     } else if (cinfo->inputctl->has_multiple_scans) {
 132       /* For a nonprogressive multiscan file, estimate 1 scan per component. */
 133       nscans = cinfo->num_components;
 134     } else {
 135       nscans = 1;
 136     }
 137     cinfo->progress->pass_counter = 0L;
 138     cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
 139     cinfo->progress->completed_passes = 0;
 140     cinfo->progress->total_passes = 1;
 141   }
 142 }