workbench/libs/jpeg/jdtrans.c

   1 /*
   2  * jdtrans.c
   3  *
   4  * Copyright (C) 1995-1997, Thomas G. Lane.
   5  * Modified 2000-2009 by Guido Vollbeding.
   6  * This file is part of the Independent JPEG Group's software.
   7  * For conditions of distribution and use, see the accompanying README file.
   8  *
   9  * This file contains library routines for transcoding decompression,
  10  * that is, reading raw DCT coefficient arrays from an input JPEG file.
  11  * The routines in jdapimin.c will also be needed by a transcoder.
  12  */
  13
  14 #define JPEG_INTERNALS
  15 #include "jinclude.h"
  16 #include "jpeglib.h"
  17
  18
  19 /* Forward declarations */
  20 LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));
  21
  22
  23 /*
  24  * Read the coefficient arrays from a JPEG file.
  25  * jpeg_read_header must be completed before calling this.
  26  *
  27  * The entire image is read into a set of virtual coefficient-block arrays,
  28  * one per component.  The return value is a pointer to the array of
  29  * virtual-array descriptors.  These can be manipulated directly via the
  30  * JPEG memory manager, or handed off to jpeg_write_coefficients().
  31  * To release the memory occupied by the virtual arrays, call
  32  * jpeg_finish_decompress() when done with the data.
  33  *
  34  * An alternative usage is to simply obtain access to the coefficient arrays
  35  * during a buffered-image-mode decompression operation.  This is allowed
  36  * after any jpeg_finish_output() call.  The arrays can be accessed until
  37  * jpeg_finish_decompress() is called.  (Note that any call to the library
  38  * may reposition the arrays, so don't rely on access_virt_barray() results
  39  * to stay valid across library calls.)
  40  *
  41  * Returns NULL if suspended.  This case need be checked only if
  42  * a suspending data source is used.
  43  */
  44
  45 GLOBAL(jvirt_barray_ptr *)
  46 jpeg_read_coefficients (j_decompress_ptr cinfo)
  47 {
  48   if (cinfo->global_state == DSTATE_READY) {
  49     /* First call: initialize active modules */
  50     transdecode_master_selection(cinfo);
  51     cinfo->global_state = DSTATE_RDCOEFS;
  52   }
  53   if (cinfo->global_state == DSTATE_RDCOEFS) {
  54     /* Absorb whole file into the coef buffer */
  55     for (;;) {
  56       int retcode;
  57       /* Call progress monitor hook if present */
  58       if (cinfo->progress != NULL)
  59         (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
  60       /* Absorb some more input */
  61       retcode = (*cinfo->inputctl->consume_input) (cinfo);
  62       if (retcode == JPEG_SUSPENDED)
  63         return NULL;
  64       if (retcode == JPEG_REACHED_EOI)
  65         break;
  66       /* Advance progress counter if appropriate */
  67       if (cinfo->progress != NULL &&
  68           (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
  69         if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
  70           /* startup underestimated number of scans; ratchet up one scan */
  71           cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
  72         }
  73       }
  74     }
  75     /* Set state so that jpeg_finish_decompress does the right thing */
  76     cinfo->global_state = DSTATE_STOPPING;
  77   }
  78   /* At this point we should be in state DSTATE_STOPPING if being used
  79    * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
  80    * to the coefficients during a full buffered-image-mode decompression.
  81    */
  82   if ((cinfo->global_state == DSTATE_STOPPING ||
  83        cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
  84     return cinfo->coef->coef_arrays;
  85   }
  86   /* Oops, improper usage */
  87   ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  88   return NULL;                  /* keep compiler happy */
  89 }
  90
  91
  92 /*
  93  * Master selection of decompression modules for transcoding.
  94  * This substitutes for jdmaster.c's initialization of the full decompressor.
  95  */
  96
  97 LOCAL(void)
  98 transdecode_master_selection (j_decompress_ptr cinfo)
  99 {
 100   /* This is effectively a buffered-image operation. */
 101   cinfo->buffered_image = TRUE;
 102
 103   /* Compute output image dimensions and related values. */
 104   jpeg_core_output_dimensions(cinfo);
 105
 106   /* Entropy decoding: either Huffman or arithmetic coding. */
 107   if (cinfo->arith_code)
 108     jinit_arith_decoder(cinfo);
 109   else {
 110     jinit_huff_decoder(cinfo);
 111   }
 112
 113   /* Always get a full-image coefficient buffer. */
 114   jinit_d_coef_controller(cinfo, TRUE);
 115
 116   /* We can now tell the memory manager to allocate virtual arrays. */
 117   (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
 118
 119   /* Initialize input side of decompressor to consume first scan. */
 120   (*cinfo->inputctl->start_input_pass) (cinfo);
 121
 122   /* Initialize progress monitoring. */
 123   if (cinfo->progress != NULL) {
 124     int nscans;
 125     /* Estimate number of scans to set pass_limit. */
 126     if (cinfo->progressive_mode) {
 127       /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
 128       nscans = 2 + 3 * cinfo->num_components;
 129     } else if (cinfo->inputctl->has_multiple_scans) {
 130       /* For a nonprogressive multiscan file, estimate 1 scan per component. */
 131       nscans = cinfo->num_components;
 132     } else {
 133       nscans = 1;
 134     }
 135     cinfo->progress->pass_counter = 0L;
 136     cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
 137     cinfo->progress->completed_passes = 0;
 138     cinfo->progress->total_passes = 1;
 139   }
 140 }