media/libjpeg/jdtrans.c

   1 /*
   2  * jdtrans.c
   3  *
   4  * This file was part of the Independent JPEG Group's software:
   5  * Copyright (C) 1995-1997, Thomas G. Lane.
   6  * libjpeg-turbo Modifications:
   7  * Copyright (C) 2020, D. R. Commander.
   8  * For conditions of distribution and use, see the accompanying README.ijg
   9  * file.
  10  *
  11  * This file contains library routines for transcoding decompression,
  12  * that is, reading raw DCT coefficient arrays from an input JPEG file.
  13  * The routines in jdapimin.c will also be needed by a transcoder.
  14  */
  15
  16 #define JPEG_INTERNALS
  17 #include "jinclude.h"
  18 #include "jpeglib.h"
  19 #include "jpegcomp.h"
  20
  21
  22 /* Forward declarations */
  23 LOCAL(void) transdecode_master_selection(j_decompress_ptr cinfo);
  24
  25
  26 /*
  27  * Read the coefficient arrays from a JPEG file.
  28  * jpeg_read_header must be completed before calling this.
  29  *
  30  * The entire image is read into a set of virtual coefficient-block arrays,
  31  * one per component.  The return value is a pointer to the array of
  32  * virtual-array descriptors.  These can be manipulated directly via the
  33  * JPEG memory manager, or handed off to jpeg_write_coefficients().
  34  * To release the memory occupied by the virtual arrays, call
  35  * jpeg_finish_decompress() when done with the data.
  36  *
  37  * An alternative usage is to simply obtain access to the coefficient arrays
  38  * during a buffered-image-mode decompression operation.  This is allowed
  39  * after any jpeg_finish_output() call.  The arrays can be accessed until
  40  * jpeg_finish_decompress() is called.  (Note that any call to the library
  41  * may reposition the arrays, so don't rely on access_virt_barray() results
  42  * to stay valid across library calls.)
  43  *
  44  * Returns NULL if suspended.  This case need be checked only if
  45  * a suspending data source is used.
  46  */
  47
  48 GLOBAL(jvirt_barray_ptr *)
  49 jpeg_read_coefficients(j_decompress_ptr cinfo)
  50 {
  51   if (cinfo->global_state == DSTATE_READY) {
  52     /* First call: initialize active modules */
  53     transdecode_master_selection(cinfo);
  54     cinfo->global_state = DSTATE_RDCOEFS;
  55   }
  56   if (cinfo->global_state == DSTATE_RDCOEFS) {
  57     /* Absorb whole file into the coef buffer */
  58     for (;;) {
  59       int retcode;
  60       /* Call progress monitor hook if present */
  61       if (cinfo->progress != NULL)
  62         (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
  63       /* Absorb some more input */
  64       retcode = (*cinfo->inputctl->consume_input) (cinfo);
  65       if (retcode == JPEG_SUSPENDED)
  66         return NULL;
  67       if (retcode == JPEG_REACHED_EOI)
  68         break;
  69       /* Advance progress counter if appropriate */
  70       if (cinfo->progress != NULL &&
  71           (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
  72         if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
  73           /* startup underestimated number of scans; ratchet up one scan */
  74           cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows;
  75         }
  76       }
  77     }
  78     /* Set state so that jpeg_finish_decompress does the right thing */
  79     cinfo->global_state = DSTATE_STOPPING;
  80   }
  81   /* At this point we should be in state DSTATE_STOPPING if being used
  82    * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
  83    * to the coefficients during a full buffered-image-mode decompression.
  84    */
  85   if ((cinfo->global_state == DSTATE_STOPPING ||
  86        cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
  87     return cinfo->coef->coef_arrays;
  88   }
  89   /* Oops, improper usage */
  90   ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  91   return NULL;                  /* keep compiler happy */
  92 }
  93
  94
  95 /*
  96  * Master selection of decompression modules for transcoding.
  97  * This substitutes for jdmaster.c's initialization of the full decompressor.
  98  */
  99
 100 LOCAL(void)
 101 transdecode_master_selection(j_decompress_ptr cinfo)
 102 {
 103   /* This is effectively a buffered-image operation. */
 104   cinfo->buffered_image = TRUE;
 105
 106 #if JPEG_LIB_VERSION >= 80
 107   /* Compute output image dimensions and related values. */
 108   jpeg_core_output_dimensions(cinfo);
 109 #endif
 110
 111   /* Entropy decoding: either Huffman or arithmetic coding. */
 112   if (cinfo->arith_code) {
 113 #ifdef D_ARITH_CODING_SUPPORTED
 114     jinit_arith_decoder(cinfo);
 115 #else
 116     ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
 117 #endif
 118   } else {
 119     if (cinfo->progressive_mode) {
 120 #ifdef D_PROGRESSIVE_SUPPORTED
 121       jinit_phuff_decoder(cinfo);
 122 #else
 123       ERREXIT(cinfo, JERR_NOT_COMPILED);
 124 #endif
 125     } else
 126       jinit_huff_decoder(cinfo);
 127   }
 128
 129   /* Always get a full-image coefficient buffer. */
 130   jinit_d_coef_controller(cinfo, TRUE);
 131
 132   /* We can now tell the memory manager to allocate virtual arrays. */
 133   (*cinfo->mem->realize_virt_arrays) ((j_common_ptr)cinfo);
 134
 135   /* Initialize input side of decompressor to consume first scan. */
 136   (*cinfo->inputctl->start_input_pass) (cinfo);
 137
 138   /* Initialize progress monitoring. */
 139   if (cinfo->progress != NULL) {
 140     int nscans;
 141     /* Estimate number of scans to set pass_limit. */
 142     if (cinfo->progressive_mode) {
 143       /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
 144       nscans = 2 + 3 * cinfo->num_components;
 145     } else if (cinfo->inputctl->has_multiple_scans) {
 146       /* For a nonprogressive multiscan file, estimate 1 scan per component. */
 147       nscans = cinfo->num_components;
 148     } else {
 149       nscans = 1;
 150     }
 151     cinfo->progress->pass_counter = 0L;
 152     cinfo->progress->pass_limit = (long)cinfo->total_iMCU_rows * nscans;
 153     cinfo->progress->completed_passes = 0;
 154     cinfo->progress->total_passes = 1;
 155   }
 156 }