jdmainct.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"

/*
 * In the current system design, the main buffer need never be a full-image
 * buffer; any full-height buffers will be found inside the coefficient or
 * postprocessing controllers.  Nonetheless, the main controller is not
 * trivial.  Its responsibility is to provide context rows for upsampling/
 * rescaling, and doing this in an efficient fashion is a bit tricky.
 *
 * Postprocessor input data is counted in "row groups".  A row group
 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
 * sample rows of each component.  (We require DCT_scaled_size values to be
 * chosen such that these numbers are integers.  In practice DCT_scaled_size
 * values will likely be powers of two, so we actually have the stronger
 * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.)
 * Upsampling will typically produce max_v_samp_factor pixel rows from each
 * row group (times any additional scale factor that the upsampler is
 * applying).
 *
 * The coefficient controller will deliver data to us one iMCU row at a time;
 * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or
 * exactly min_DCT_scaled_size row groups.  (This amount of data corresponds
 * to one row of MCUs when the image is fully interleaved.)  Note that the
 * number of sample rows varies across components, but the number of row
 * groups does not.  Some garbage sample rows may be included in the last iMCU
 * row at the bottom of the image.
 *
 * Depending on the vertical scaling algorithm used, the upsampler may need
 * access to the sample row(s) above and below its current input row group.
 * The upsampler is required to set need_context_rows TRUE at global selection
 * time if so.  When need_context_rows is FALSE, this controller can simply
 * obtain one iMCU row at a time from the coefficient controller and dole it
 * out as row groups to the postprocessor.
 *
 * When need_context_rows is TRUE, this controller guarantees that the buffer
 * passed to postprocessing contains at least one row group's worth of samples
 * above and below the row group(s) being processed.  Note that the context
 * rows "above" the first passed row group appear at negative row offsets in
 * the passed buffer.  At the top and bottom of the image, the required
 * context rows are manufactured by duplicating the first or last real sample
 * row; this avoids having special cases in the upsampling inner loops.
 *
 * The amount of context is fixed at one row group just because that's a
 * convenient number for this controller to work with.  The existing
 * upsamplers really only need one sample row of context.  An upsampler
 * supporting arbitrary output rescaling might wish for more than one row
 * group of context when shrinking the image; tough, we don't handle that.
 * (This is justified by the assumption that downsizing will be handled mostly
 * by adjusting the DCT_scaled_size values, so that the actual scale factor at
 * the upsample step needn't be much less than one.)
 *
 * To provide the desired context, we have to retain the last two row groups
 * of one iMCU row while reading in the next iMCU row.  (The last row group
 * can't be processed until we have another row group for its below-context,
 * and so we have to save the next-to-last group too for its above-context.)
 * We could do this most simply by copying data around in our buffer, but
 * that'd be very slow.  We can avoid copying any data by creating a rather
 * strange pointer structure.  Here's how it works.  We allocate a workspace
 * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number
 * of row groups per iMCU row).  We create two sets of redundant pointers to
 * the workspace.  Labeling the physical row groups 0 to M+1, the synthesized
 * pointer lists look like this:
 *                   M+1                          M-1
 * master pointer --> 0         master pointer --> 0
 *                    1                            1
 *                   ...                          ...
 *                   M-3                          M-3
 *                   M-2                           M
 *                   M-1                          M+1
 *                    M                           M-2
 *                   M+1                          M-1
 *                    0                            0
 * We read alternate iMCU rows using each master pointer; thus the last two
 * row groups of the previous iMCU row remain un-overwritten in the workspace.
 * The pointer lists are set up so that the required context rows appear to
 * be adjacent to the proper places when we pass the pointer lists to the
 * upsampler.
 *
 * The above pictures describe the normal state of the pointer lists.
 * At top and bottom of the image, we diddle the pointer lists to duplicate
 * the first or last sample row as necessary (this is cheaper than copying
 * sample rows around).
 *
 * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1.  In that
 * situation each iMCU row provides only one row group so the buffering logic
 * must be different (eg, we must read two iMCU rows before we can emit the
 * first row group).  For now, we simply do not support providing context
 * rows when min_DCT_scaled_size is 1.  That combination seems unlikely to
 * be worth providing --- if someone wants a 1/8th-size preview, they probably
 * want it quick and dirty, so a context-free upsampler is sufficient.
 */

/* Private buffer controller object */

typedef struct
{
        struct jpeg_d_main_controller pub; /* public fields */

        /* Pointer to allocated workspace (M or M+2 row groups). */
        JSAMPARRAY buffer[MAX_COMPONENTS];

        boolean buffer_full; /* Have we gotten an iMCU row from decoder? */
        JDIMENSION rowgroup_ctr; /* counts row groups output to postprocessor */

        /* Remaining fields are only used in the context case. */

        /* These are the master pointers to the funny-order pointer lists. */
        JSAMPIMAGE xbuffer[2]; /* pointers to weird pointer lists */

        int whichptr; /* indicates which pointer set is now in use */
        int context_state; /* process_data state machine status */
        JDIMENSION rowgroups_avail; /* row groups available to postprocessor */
        JDIMENSION iMCU_row_ctr; /* counts iMCU rows to detect image top/bot */
} my_main_controller;

typedef my_main_controller* my_main_ptr;

/* context_state values: */
#define CTX_PREPARE_FOR_IMCU 0 /* need to prepare for MCU row */
#define CTX_PROCESS_IMCU 1 /* feeding iMCU to postprocessor */
#define CTX_POSTPONED_ROW 2 /* feeding postponed row group */

/* Forward declarations */
METHODDEF(void)
process_data_simple_main JPP(
        (j_decompress_ptr cinfo, JSAMPARRAY output_buf, JDIMENSION* out_row_ctr,
         JDIMENSION out_rows_avail));
METHODDEF(void)
process_data_context_main JPP(
        (j_decompress_ptr cinfo, JSAMPARRAY output_buf, JDIMENSION* out_row_ctr,
         JDIMENSION out_rows_avail));
#ifdef QUANT_2PASS_SUPPORTED
METHODDEF(void)
process_data_crank_post JPP(
        (j_decompress_ptr cinfo, JSAMPARRAY output_buf, JDIMENSION* out_row_ctr,
         JDIMENSION out_rows_avail));
#endif

LOCAL(void)
alloc_funny_pointers(j_decompress_ptr cinfo)
/* Allocate space for the funny pointer lists.
 * This is done only once, not once per pass.
 */
{
        my_main_ptr main = (my_main_ptr)cinfo->main;
        int ci, rgroup;
        int M = cinfo->min_DCT_scaled_size;
        jpeg_component_info* compptr;
        JSAMPARRAY xbuf;

        /* Get top-level space for component array pointers.
         * We alloc both arrays with one call to save a few cycles.
         */
        main->xbuffer[0] = (JSAMPIMAGE)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_IMAGE,
                cinfo->num_components * 2 * SIZEOF(JSAMPARRAY));
        main->xbuffer[1] = main->xbuffer[0] + cinfo->num_components;

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                rgroup =
                        (compptr->v_samp_factor * compptr->DCT_scaled_size) /
                        cinfo->min_DCT_scaled_size; /* height of a row group of component */
                /* Get space for pointer lists --- M+4 row groups in each list.
                 * We alloc both pointer lists with one call to save a few cycles.
                 */
                xbuf = (JSAMPARRAY)(*cinfo->mem->alloc_small)(
                        (j_common_ptr)cinfo, JPOOL_IMAGE,
                        2 * (rgroup * (M + 4)) * SIZEOF(JSAMPROW));
                xbuf += rgroup; /* want one row group at negative offsets */
                main->xbuffer[0][ci] = xbuf;
                xbuf += rgroup * (M + 4);
                main->xbuffer[1][ci] = xbuf;
        }
}

LOCAL(void)
make_funny_pointers(j_decompress_ptr cinfo)
/* Create the funny pointer lists discussed in the comments above.
 * The actual workspace is already allocated (in main->buffer),
 * and the space for the pointer lists is allocated too.
 * This routine just fills in the curiously ordered lists.
 * This will be repeated at the beginning of each pass.
 */
{
        my_main_ptr main = (my_main_ptr)cinfo->main;
        int ci, i, rgroup;
        int M = cinfo->min_DCT_scaled_size;
        jpeg_component_info* compptr;
        JSAMPARRAY buf, xbuf0, xbuf1;

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                rgroup =
                        (compptr->v_samp_factor * compptr->DCT_scaled_size) /
                        cinfo->min_DCT_scaled_size; /* height of a row group of component */
                xbuf0 = main->xbuffer[0][ci];
                xbuf1 = main->xbuffer[1][ci];
                /* First copy the workspace pointers as-is */
                buf = main->buffer[ci];
                for (i = 0; i < rgroup * (M + 2); i++)
                {
                        xbuf0[i] = xbuf1[i] = buf[i];
                }
                /* In the second list, put the last four row groups in swapped order */
                for (i = 0; i < rgroup * 2; i++)
                {
                        xbuf1[rgroup * (M - 2) + i] = buf[rgroup * M + i];
                        xbuf1[rgroup * M + i] = buf[rgroup * (M - 2) + i];
                }
                /* The wraparound pointers at top and bottom will be filled later
                 * (see set_wraparound_pointers, below).  Initially we want the "above"
                 * pointers to duplicate the first actual data line.  This only needs
                 * to happen in xbuffer[0].
                 */
                for (i = 0; i < rgroup; i++)
                {
                        xbuf0[i - rgroup] = xbuf0[0];
                }
        }
}

LOCAL(void)
set_wraparound_pointers(j_decompress_ptr cinfo)
/* Set up the "wraparound" pointers at top and bottom of the pointer lists.
 * This changes the pointer list state from top-of-image to the normal state.
 */
{
        my_main_ptr main = (my_main_ptr)cinfo->main;
        int ci, i, rgroup;
        int M = cinfo->min_DCT_scaled_size;
        jpeg_component_info* compptr;
        JSAMPARRAY xbuf0, xbuf1;

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                rgroup =
                        (compptr->v_samp_factor * compptr->DCT_scaled_size) /
                        cinfo->min_DCT_scaled_size; /* height of a row group of component */
                xbuf0 = main->xbuffer[0][ci];
                xbuf1 = main->xbuffer[1][ci];
                for (i = 0; i < rgroup; i++)
                {
                        xbuf0[i - rgroup] = xbuf0[rgroup * (M + 1) + i];
                        xbuf1[i - rgroup] = xbuf1[rgroup * (M + 1) + i];
                        xbuf0[rgroup * (M + 2) + i] = xbuf0[i];
                        xbuf1[rgroup * (M + 2) + i] = xbuf1[i];
                }
        }
}

LOCAL(void)
set_bottom_pointers(j_decompress_ptr cinfo)
/* Change the pointer lists to duplicate the last sample row at the bottom
 * of the image.  whichptr indicates which xbuffer holds the final iMCU row.
 * Also sets rowgroups_avail to indicate number of nondummy row groups in row.
 */
{
        my_main_ptr main = (my_main_ptr)cinfo->main;
        int ci, i, rgroup, iMCUheight, rows_left;
        jpeg_component_info* compptr;
        JSAMPARRAY xbuf;

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                /* Count sample rows in one iMCU row and in one row group */
                iMCUheight = compptr->v_samp_factor * compptr->DCT_scaled_size;
                rgroup = iMCUheight / cinfo->min_DCT_scaled_size;
                /* Count nondummy sample rows remaining for this component */
                rows_left = (int)(compptr->downsampled_height % (JDIMENSION)iMCUheight);
                if (rows_left == 0) rows_left = iMCUheight;
                /* Count nondummy row groups.  Should get same answer for each
                 * component,
                 * so we need only do it once.
                 */
                if (ci == 0)
                {
                        main->rowgroups_avail = (JDIMENSION)((rows_left - 1) / rgroup + 1);
                }
                /* Duplicate the last real sample row rgroup*2 times; this pads out the
                 * last partial rowgroup and ensures at least one full rowgroup of
                 * context.
                 */
                xbuf = main->xbuffer[main->whichptr][ci];
                for (i = 0; i < rgroup * 2; i++)
                {
                        xbuf[rows_left + i] = xbuf[rows_left - 1];
                }
        }
}

/*
 * Initialize for a processing pass.
 */

METHODDEF(void)
start_pass_main(j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
{
        my_main_ptr main = (my_main_ptr)cinfo->main;

        switch (pass_mode)
        {
                case JBUF_PASS_THRU:
                        if (cinfo->upsample->need_context_rows)
                        {
                                main->pub.process_data = process_data_context_main;
                                make_funny_pointers(cinfo); /* Create the xbuffer[] lists */
                                main->whichptr = 0; /* Read first iMCU row into xbuffer[0] */
                                main->context_state = CTX_PREPARE_FOR_IMCU;
                                main->iMCU_row_ctr = 0;
                        }
                        else
                        {
                                /* Simple case with no context needed */
                                main->pub.process_data = process_data_simple_main;
                        }
                        main->buffer_full = FALSE; /* Mark buffer empty */
                        main->rowgroup_ctr = 0;
                        break;
#ifdef QUANT_2PASS_SUPPORTED
                case JBUF_CRANK_DEST:
                        /* For last pass of 2-pass quantization, just crank the
                         * postprocessor */
                        main->pub.process_data = process_data_crank_post;
                        break;
#endif
                default:
                        ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
                        break;
        }
}

/*
 * Process some data.
 * This handles the simple case where no context is required.
 */

METHODDEF(void)
process_data_simple_main(
        j_decompress_ptr cinfo, JSAMPARRAY output_buf, JDIMENSION* out_row_ctr,
        JDIMENSION out_rows_avail)
{
        my_main_ptr main = (my_main_ptr)cinfo->main;
        JDIMENSION rowgroups_avail;

        /* Read input data if we haven't filled the main buffer yet */
        if (!main->buffer_full)
        {
                if (!(*cinfo->coef->decompress_data)(cinfo, main->buffer))
                        return; /* suspension forced, can do nothing more */
                main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */
        }

        /* There are always min_DCT_scaled_size row groups in an iMCU row. */
        rowgroups_avail = (JDIMENSION)cinfo->min_DCT_scaled_size;
        /* Note: at the bottom of the image, we may pass extra garbage row groups
         * to the postprocessor.  The postprocessor has to check for bottom
         * of image anyway (at row resolution), so no point in us doing it too.
         */

        /* Feed the postprocessor */
        (*cinfo->post->post_process_data)(
                cinfo, main->buffer, &main->rowgroup_ctr, rowgroups_avail, output_buf,
                out_row_ctr, out_rows_avail);

        /* Has postprocessor consumed all the data yet? If so, mark buffer empty */
        if (main->rowgroup_ctr >= rowgroups_avail)
        {
                main->buffer_full = FALSE;
                main->rowgroup_ctr = 0;
        }
}

/*
 * Process some data.
 * This handles the case where context rows must be provided.
 */

METHODDEF(void)
process_data_context_main(
        j_decompress_ptr cinfo, JSAMPARRAY output_buf, JDIMENSION* out_row_ctr,
        JDIMENSION out_rows_avail)
{
        my_main_ptr main = (my_main_ptr)cinfo->main;

        /* Read input data if we haven't filled the main buffer yet */
        if (!main->buffer_full)
        {
                if (!(*cinfo->coef->decompress_data)(
                                cinfo, main->xbuffer[main->whichptr]))
                        return; /* suspension forced, can do nothing more */
                main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */
                main->iMCU_row_ctr++; /* count rows received */
        }

        /* Postprocessor typically will not swallow all the input data it is handed
         * in one call (due to filling the output buffer first).  Must be prepared
         * to exit and restart.  This switch lets us keep track of how far we got.
         * Note that each case falls through to the next on successful completion.
         */
        switch (main->context_state)
        {
                case CTX_POSTPONED_ROW:
                        /* Call postprocessor using previously set pointers for postponed
                         * row */
                        (*cinfo->post->post_process_data)(
                                cinfo, main->xbuffer[main->whichptr], &main->rowgroup_ctr,
                                main->rowgroups_avail, output_buf, out_row_ctr, out_rows_avail);
                        if (main->rowgroup_ctr < main->rowgroups_avail)
                                return; /* Need to suspend */
                        main->context_state = CTX_PREPARE_FOR_IMCU;
                        if (*out_row_ctr >= out_rows_avail)
                                return; /* Postprocessor exactly filled output buf */
                /*FALLTHROUGH*/
                case CTX_PREPARE_FOR_IMCU:
                        /* Prepare to process first M-1 row groups of this iMCU row */
                        main->rowgroup_ctr = 0;
                        main->rowgroups_avail =
                                (JDIMENSION)(cinfo->min_DCT_scaled_size - 1);
                        /* Check for bottom of image: if so, tweak pointers to "duplicate"
                         * the last sample row, and adjust rowgroups_avail to ignore padding
                         * rows.
                         */
                        if (main->iMCU_row_ctr == cinfo->total_iMCU_rows)
                                set_bottom_pointers(cinfo);
                        main->context_state = CTX_PROCESS_IMCU;
                /*FALLTHROUGH*/
                case CTX_PROCESS_IMCU:
                        /* Call postprocessor using previously set pointers */
                        (*cinfo->post->post_process_data)(
                                cinfo, main->xbuffer[main->whichptr], &main->rowgroup_ctr,
                                main->rowgroups_avail, output_buf, out_row_ctr, out_rows_avail);
                        if (main->rowgroup_ctr < main->rowgroups_avail)
                                return; /* Need to suspend */
                        /* After the first iMCU, change wraparound pointers to normal state
                         */
                        if (main->iMCU_row_ctr == 1) set_wraparound_pointers(cinfo);
                        /* Prepare to load new iMCU row using other xbuffer list */
                        main->whichptr ^= 1; /* 0=>1 or 1=>0 */
                        main->buffer_full = FALSE;
                        /* Still need to process last row group of this iMCU row, */
                        /* which is saved at index M+1 of the other xbuffer */
                        main->rowgroup_ctr = (JDIMENSION)(cinfo->min_DCT_scaled_size + 1);
                        main->rowgroups_avail =
                                (JDIMENSION)(cinfo->min_DCT_scaled_size + 2);
                        main->context_state = CTX_POSTPONED_ROW;
        }
}

/*
 * Process some data.
 * Final pass of two-pass quantization: just call the postprocessor.
 * Source data will be the postprocessor controller's internal buffer.
 */

#ifdef QUANT_2PASS_SUPPORTED

METHODDEF(void)
process_data_crank_post(
        j_decompress_ptr cinfo, JSAMPARRAY output_buf, JDIMENSION* out_row_ctr,
        JDIMENSION out_rows_avail)
{
        (*cinfo->post->post_process_data)(
                cinfo, (JSAMPIMAGE) nullptr, (JDIMENSION*)nullptr, (JDIMENSION)0,
                output_buf, out_row_ctr, out_rows_avail);
}

#endif /* QUANT_2PASS_SUPPORTED */

/*
 * Initialize main buffer controller.
 */

GLOBAL(void)
jinit_d_main_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
{
        my_main_ptr main;
        int ci, rgroup, ngroups;
        jpeg_component_info* compptr;

        main = (my_main_ptr)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_IMAGE, SIZEOF(my_main_controller));
        cinfo->main = (struct jpeg_d_main_controller*)main;
        main->pub.start_pass = start_pass_main;

        if (need_full_buffer) /* shouldn't happen */
                ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

        /* Allocate the workspace.
         * ngroups is the number of row groups we need.
         */
        if (cinfo->upsample->need_context_rows)
        {
                if (cinfo->min_DCT_scaled_size <
                        2) /* unsupported, see comments above */
                        ERREXIT(cinfo, JERR_NOTIMPL);
                alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */
                ngroups = cinfo->min_DCT_scaled_size + 2;
        }
        else
        {
                ngroups = cinfo->min_DCT_scaled_size;
        }

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                rgroup =
                        (compptr->v_samp_factor * compptr->DCT_scaled_size) /
                        cinfo->min_DCT_scaled_size; /* height of a row group of component */
                main->buffer[ci] = (*cinfo->mem->alloc_sarray)(
                        (j_common_ptr)cinfo, JPOOL_IMAGE,
                        compptr->width_in_blocks * compptr->DCT_scaled_size,
                        (JDIMENSION)(rgroup * ngroups));
        }
}