jdtrans.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */

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

/* Forward declarations */
LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));

/*
 * Read the coefficient arrays from a JPEG file.
 * jpeg_read_header must be completed before calling this.
 *
 * The entire image is read into a set of virtual coefficient-block arrays,
 * one per component.  The return value is a pointer to the array of
 * virtual-array descriptors.  These can be manipulated directly via the
 * JPEG memory manager, or handed off to jpeg_write_coefficients().
 * To release the memory occupied by the virtual arrays, call
 * jpeg_finish_decompress() when done with the data.
 *
 * An alternative usage is to simply obtain access to the coefficient arrays
 * during a buffered-image-mode decompression operation.  This is allowed
 * after any jpeg_finish_output() call.  The arrays can be accessed until
 * jpeg_finish_decompress() is called.  (Note that any call to the library
 * may reposition the arrays, so don't rely on access_virt_barray() results
 * to stay valid across library calls.)
 *
 * Returns nullptr if suspended.  This case need be checked only if
 * a suspending data source is used.
 */

GLOBAL(jvirt_barray_ptr*)
jpeg_read_coefficients(j_decompress_ptr cinfo)
{
        if (cinfo->global_state == DSTATE_READY)
        {
                /* First call: initialize active modules */
                transdecode_master_selection(cinfo);
                cinfo->global_state = DSTATE_RDCOEFS;
        }
        if (cinfo->global_state == DSTATE_RDCOEFS)
        {
                /* Absorb whole file into the coef buffer */
                for (;;)
                {
                        int retcode;
                        /* Call progress monitor hook if present */
                        if (cinfo->progress != nullptr)
                                (*cinfo->progress->progress_monitor)((j_common_ptr)cinfo);
                        /* Absorb some more input */
                        retcode = (*cinfo->inputctl->consume_input)(cinfo);
                        if (retcode == JPEG_SUSPENDED) return nullptr;
                        if (retcode == JPEG_REACHED_EOI) break;
                        /* Advance progress counter if appropriate */
                        if (cinfo->progress != nullptr &&
                                (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS))
                        {
                                if (++cinfo->progress->pass_counter >=
                                        cinfo->progress->pass_limit)
                                {
                                        /* startup underestimated number of scans; ratchet up one
                                         * scan */
                                        cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows;
                                }
                        }
                }
                /* Set state so that jpeg_finish_decompress does the right thing */
                cinfo->global_state = DSTATE_STOPPING;
        }
        /* At this point we should be in state DSTATE_STOPPING if being used
         * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
         * to the coefficients during a full buffered-image-mode decompression.
         */
        if ((cinfo->global_state == DSTATE_STOPPING ||
                 cinfo->global_state == DSTATE_BUFIMAGE) &&
                cinfo->buffered_image)
        {
                return cinfo->coef->coef_arrays;
        }
        /* Oops, improper usage */
        ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
        return nullptr; /* keep compiler happy */
}

/*
 * Master selection of decompression modules for transcoding.
 * This substitutes for jdmaster.c's initialization of the full decompressor.
 */

LOCAL(void)
transdecode_master_selection(j_decompress_ptr cinfo)
{
        /* This is effectively a buffered-image operation. */
        cinfo->buffered_image = TRUE;

        /* Entropy decoding: either Huffman or arithmetic coding. */
        if (cinfo->arith_code)
        {
                ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
        }
        else
        {
                if (cinfo->progressive_mode)
                {
#ifdef D_PROGRESSIVE_SUPPORTED
                        jinit_phuff_decoder(cinfo);
#else
                        ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
                }
                else
                        jinit_huff_decoder(cinfo);
        }

        /* Always get a full-image coefficient buffer. */
        jinit_d_coef_controller(cinfo, TRUE);

        /* We can now tell the memory manager to allocate virtual arrays. */
        (*cinfo->mem->realize_virt_arrays)((j_common_ptr)cinfo);

        /* Initialize input side of decompressor to consume first scan. */
        (*cinfo->inputctl->start_input_pass)(cinfo);

        /* Initialize progress monitoring. */
        if (cinfo->progress != nullptr)
        {
                int nscans;
                /* Estimate number of scans to set pass_limit. */
                if (cinfo->progressive_mode)
                {
                        /* Arbitrarily estimate 2 interleaved DC scans + 3 AC
                         * scans/component. */
                        nscans = 2 + 3 * cinfo->num_components;
                }
                else if (cinfo->inputctl->has_multiple_scans)
                {
                        /* For a nonprogressive multiscan file, estimate 1 scan per
                         * component. */
                        nscans = cinfo->num_components;
                }
                else
                {
                        nscans = 1;
                }
                cinfo->progress->pass_counter = 0L;
                cinfo->progress->pass_limit = (long)cinfo->total_iMCU_rows * nscans;
                cinfo->progress->completed_passes = 0;
                cinfo->progress->total_passes = 1;
        }
}