jdcoefct.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"

/* Block smoothing is only applicable for progressive JPEG, so: */
#ifndef D_PROGRESSIVE_SUPPORTED
#undef BLOCK_SMOOTHING_SUPPORTED
#endif

/* Private buffer controller object */

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

        /* These variables keep track of the current location of the input side. */
        /* cinfo->input_iMCU_row is also used for this. */
        JDIMENSION MCU_ctr; /* counts MCUs processed in current row */
        int MCU_vert_offset; /* counts MCU rows within iMCU row */
        int MCU_rows_per_iMCU_row; /* number of such rows needed */

        /* The output side's location is represented by cinfo->output_iMCU_row. */

        /* In single-pass modes, it's sufficient to buffer just one MCU.
         * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
         * and let the entropy decoder write into that workspace each time.
         * (On 80x86, the workspace is FAR even though it's not really very big;
         * this is to keep the module interfaces unchanged when a large coefficient
         * buffer is necessary.)
         * In multi-pass modes, this array points to the current MCU's blocks
         * within the virtual arrays; it is used only by the input side.
         */
        JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];

#ifdef D_MULTISCAN_FILES_SUPPORTED
        /* In multi-pass modes, we need a virtual block array for each component. */
        jvirt_barray_ptr whole_image[MAX_COMPONENTS];
#endif

#ifdef BLOCK_SMOOTHING_SUPPORTED
        /* When doing block smoothing, we latch coefficient Al values here */
        int* coef_bits_latch;
#define SAVED_COEFS 6 /* we save coef_bits[0..5] */
#endif
} my_coef_controller;

typedef my_coef_controller* my_coef_ptr;

/* Forward declarations */
METHODDEF(int)
decompress_onepass JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
#ifdef D_MULTISCAN_FILES_SUPPORTED
METHODDEF(int)
decompress_data JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
#endif
#ifdef BLOCK_SMOOTHING_SUPPORTED
LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
METHODDEF(int)
decompress_smooth_data JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
#endif

LOCAL(void)
start_iMCU_row(j_decompress_ptr cinfo)
/* Reset within-iMCU-row counters for a new row (input side) */
{
        my_coef_ptr coef = (my_coef_ptr)cinfo->coef;

        /* In an interleaved scan, an MCU row is the same as an iMCU row.
         * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
         * But at the bottom of the image, process only what's left.
         */
        if (cinfo->comps_in_scan > 1)
        {
                coef->MCU_rows_per_iMCU_row = 1;
        }
        else
        {
                if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows - 1))
                        coef->MCU_rows_per_iMCU_row =
                                cinfo->cur_comp_info[0]->v_samp_factor;
                else
                        coef->MCU_rows_per_iMCU_row =
                                cinfo->cur_comp_info[0]->last_row_height;
        }

        coef->MCU_ctr = 0;
        coef->MCU_vert_offset = 0;
}

/*
 * Initialize for an input processing pass.
 */

METHODDEF(void)
start_input_pass(j_decompress_ptr cinfo)
{
        cinfo->input_iMCU_row = 0;
        start_iMCU_row(cinfo);
}

/*
 * Initialize for an output processing pass.
 */

METHODDEF(void)
start_output_pass(j_decompress_ptr cinfo)
{
#ifdef BLOCK_SMOOTHING_SUPPORTED
        my_coef_ptr coef = (my_coef_ptr)cinfo->coef;

        /* If multipass, check to see whether to use block smoothing on this pass */
        if (coef->pub.coef_arrays != nullptr)
        {
                if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
                        coef->pub.decompress_data = decompress_smooth_data;
                else
                        coef->pub.decompress_data = decompress_data;
        }
#endif
        cinfo->output_iMCU_row = 0;
}

/*
 * Decompress and return some data in the single-pass case.
 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 * Input and output must run in lockstep since we have only a one-MCU buffer.
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 *
 * NB: output_buf contains a plane for each component in image,
 * which we index according to the component's SOF position.
 */

METHODDEF(int)
decompress_onepass(j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
        my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
        JDIMENSION MCU_col_num; /* index of current MCU within row */
        JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
        JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
        int blkn, ci, xindex, yindex, yoffset, useful_width;
        JSAMPARRAY output_ptr;
        JDIMENSION start_col, output_col;
        jpeg_component_info* compptr;
        inverse_DCT_method_ptr inverse_DCT;

        /* Loop to process as much as one whole iMCU row */
        for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
                 yoffset++)
        {
                for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
                         MCU_col_num++)
                {
                        /* Try to fetch an MCU.  Entropy decoder expects buffer to be
                         * zeroed. */
                        jzero_far(
                                (void FAR*)coef->MCU_buffer[0],
                                (size_t)(cinfo->blocks_in_MCU * SIZEOF(JBLOCK)));
                        if (!(*cinfo->entropy->decode_mcu)(cinfo, coef->MCU_buffer))
                        {
                                /* Suspension forced; update state counters and exit */
                                coef->MCU_vert_offset = yoffset;
                                coef->MCU_ctr = MCU_col_num;
                                return JPEG_SUSPENDED;
                        }
                        /* Determine where data should go in output_buf and do the IDCT
                         * thing.
                         * We skip dummy blocks at the right and bottom edges (but blkn gets
                         * incremented past them!).  Note the inner loop relies on having
                         * allocated the MCU_buffer[] blocks sequentially.
                         */
                        blkn = 0; /* index of current DCT block within MCU */
                        for (ci = 0; ci < cinfo->comps_in_scan; ci++)
                        {
                                compptr = cinfo->cur_comp_info[ci];
                                /* Don't bother to IDCT an uninteresting component. */
                                if (!compptr->component_needed)
                                {
                                        blkn += compptr->MCU_blocks;
                                        continue;
                                }
                                inverse_DCT =
                                        cinfo->idct->inverse_DCT[compptr->component_index];
                                useful_width = (MCU_col_num < last_MCU_col)
                                                                   ? compptr->MCU_width
                                                                   : compptr->last_col_width;
                                output_ptr = output_buf[compptr->component_index] +
                                                         yoffset * compptr->DCT_scaled_size;
                                start_col = MCU_col_num * compptr->MCU_sample_width;
                                for (yindex = 0; yindex < compptr->MCU_height; yindex++)
                                {
                                        if (cinfo->input_iMCU_row < last_iMCU_row ||
                                                yoffset + yindex < compptr->last_row_height)
                                        {
                                                output_col = start_col;
                                                for (xindex = 0; xindex < useful_width; xindex++)
                                                {
                                                        (*inverse_DCT)(
                                                                cinfo, compptr,
                                                                (JCOEFPTR)coef->MCU_buffer[blkn + xindex],
                                                                output_ptr, output_col);
                                                        output_col += compptr->DCT_scaled_size;
                                                }
                                        }
                                        blkn += compptr->MCU_width;
                                        output_ptr += compptr->DCT_scaled_size;
                                }
                        }
                }
                /* Completed an MCU row, but perhaps not an iMCU row */
                coef->MCU_ctr = 0;
        }
        /* Completed the iMCU row, advance counters for next one */
        cinfo->output_iMCU_row++;
        if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows)
        {
                start_iMCU_row(cinfo);
                return JPEG_ROW_COMPLETED;
        }
        /* Completed the scan */
        (*cinfo->inputctl->finish_input_pass)(cinfo);
        return JPEG_SCAN_COMPLETED;
}

/*
 * Dummy consume-input routine for single-pass operation.
 */

METHODDEF(int)
dummy_consume_data(j_decompress_ptr)
{
        return JPEG_SUSPENDED; /* Always indicate nothing was done */
}

#ifdef D_MULTISCAN_FILES_SUPPORTED

/*
 * Consume input data and store it in the full-image coefficient buffer.
 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
 * ie, v_samp_factor block rows for each component in the scan.
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 */

METHODDEF(int)
consume_data(j_decompress_ptr cinfo)
{
        my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
        JDIMENSION MCU_col_num; /* index of current MCU within row */
        int blkn, ci, xindex, yindex, yoffset;
        JDIMENSION start_col;
        JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
        JBLOCKROW buffer_ptr;
        jpeg_component_info* compptr;

        /* Align the virtual buffers for the components used in this scan. */
        for (ci = 0; ci < cinfo->comps_in_scan; ci++)
        {
                compptr = cinfo->cur_comp_info[ci];
                buffer[ci] = (*cinfo->mem->access_virt_barray)(
                        (j_common_ptr)cinfo, coef->whole_image[compptr->component_index],
                        cinfo->input_iMCU_row * compptr->v_samp_factor,
                        (JDIMENSION)compptr->v_samp_factor, TRUE);
                /* Note: entropy decoder expects buffer to be zeroed,
                 * but this is handled automatically by the memory manager
                 * because we requested a pre-zeroed array.
                 */
        }

        /* Loop to process one whole iMCU row */
        for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
                 yoffset++)
        {
                for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
                         MCU_col_num++)
                {
                        /* Construct list of pointers to DCT blocks belonging to this MCU */
                        blkn = 0; /* index of current DCT block within MCU */
                        for (ci = 0; ci < cinfo->comps_in_scan; ci++)
                        {
                                compptr = cinfo->cur_comp_info[ci];
                                start_col = MCU_col_num * compptr->MCU_width;
                                for (yindex = 0; yindex < compptr->MCU_height; yindex++)
                                {
                                        buffer_ptr = buffer[ci][yindex + yoffset] + start_col;
                                        for (xindex = 0; xindex < compptr->MCU_width; xindex++)
                                        {
                                                coef->MCU_buffer[blkn++] = buffer_ptr++;
                                        }
                                }
                        }
                        /* Try to fetch the MCU. */
                        if (!(*cinfo->entropy->decode_mcu)(cinfo, coef->MCU_buffer))
                        {
                                /* Suspension forced; update state counters and exit */
                                coef->MCU_vert_offset = yoffset;
                                coef->MCU_ctr = MCU_col_num;
                                return JPEG_SUSPENDED;
                        }
                }
                /* Completed an MCU row, but perhaps not an iMCU row */
                coef->MCU_ctr = 0;
        }
        /* Completed the iMCU row, advance counters for next one */
        if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows)
        {
                start_iMCU_row(cinfo);
                return JPEG_ROW_COMPLETED;
        }
        /* Completed the scan */
        (*cinfo->inputctl->finish_input_pass)(cinfo);
        return JPEG_SCAN_COMPLETED;
}

/*
 * Decompress and return some data in the multi-pass case.
 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 *
 * NB: output_buf contains a plane for each component in image.
 */

METHODDEF(int)
decompress_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
        my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
        JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
        JDIMENSION block_num;
        int ci, block_row, block_rows;
        JBLOCKARRAY buffer;
        JBLOCKROW buffer_ptr;
        JSAMPARRAY output_ptr;
        JDIMENSION output_col;
        jpeg_component_info* compptr;
        inverse_DCT_method_ptr inverse_DCT;

        /* Force some input to be done if we are getting ahead of the input. */
        while (cinfo->input_scan_number < cinfo->output_scan_number ||
                   (cinfo->input_scan_number == cinfo->output_scan_number &&
                        cinfo->input_iMCU_row <= cinfo->output_iMCU_row))
        {
                if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
                        return JPEG_SUSPENDED;
        }

        /* OK, output from the virtual arrays. */
        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                /* Don't bother to IDCT an uninteresting component. */
                if (!compptr->component_needed) continue;
                /* Align the virtual buffer for this component. */
                buffer = (*cinfo->mem->access_virt_barray)(
                        (j_common_ptr)cinfo, coef->whole_image[ci],
                        cinfo->output_iMCU_row * compptr->v_samp_factor,
                        (JDIMENSION)compptr->v_samp_factor, FALSE);
                /* Count non-dummy DCT block rows in this iMCU row. */
                if (cinfo->output_iMCU_row < last_iMCU_row)
                        block_rows = compptr->v_samp_factor;
                else
                {
                        /* NB: can't use last_row_height here; it is input-side-dependent!
                         */
                        block_rows =
                                (int)(compptr->height_in_blocks % compptr->v_samp_factor);
                        if (block_rows == 0) block_rows = compptr->v_samp_factor;
                }
                inverse_DCT = cinfo->idct->inverse_DCT[ci];
                output_ptr = output_buf[ci];
                /* Loop over all DCT blocks to be processed. */
                for (block_row = 0; block_row < block_rows; block_row++)
                {
                        buffer_ptr = buffer[block_row];
                        output_col = 0;
                        for (block_num = 0; block_num < compptr->width_in_blocks;
                                 block_num++)
                        {
                                (*inverse_DCT)(
                                        cinfo, compptr, (JCOEFPTR)buffer_ptr, output_ptr,
                                        output_col);
                                buffer_ptr++;
                                output_col += compptr->DCT_scaled_size;
                        }
                        output_ptr += compptr->DCT_scaled_size;
                }
        }

        if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
                return JPEG_ROW_COMPLETED;
        return JPEG_SCAN_COMPLETED;
}

#endif /* D_MULTISCAN_FILES_SUPPORTED */

#ifdef BLOCK_SMOOTHING_SUPPORTED

/*
 * This code applies interblock smoothing as described by section K.8
 * of the JPEG standard: the first 5 AC coefficients are estimated from
 * the DC values of a DCT block and its 8 neighboring blocks.
 * We apply smoothing only for progressive JPEG decoding, and only if
 * the coefficients it can estimate are not yet known to full precision.
 */

/* Natural-order array positions of the first 5 zigzag-order coefficients */
#define Q01_POS 1
#define Q10_POS 8
#define Q20_POS 16
#define Q11_POS 9
#define Q02_POS 2

/*
 * Determine whether block smoothing is applicable and safe.
 * We also latch the current states of the coef_bits[] entries for the
 * AC coefficients; otherwise, if the input side of the decompressor
 * advances into a new scan, we might think the coefficients are known
 * more accurately than they really are.
 */

LOCAL(boolean)
smoothing_ok(j_decompress_ptr cinfo)
{
        my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
        boolean smoothing_useful = FALSE;
        int ci, coefi;
        jpeg_component_info* compptr;
        JQUANT_TBL* qtable;
        int* coef_bits;
        int* coef_bits_latch;

        if (!cinfo->progressive_mode || cinfo->coef_bits == nullptr) return FALSE;

        /* Allocate latch area if not already done */
        if (coef->coef_bits_latch == nullptr)
                coef->coef_bits_latch = (int*)(*cinfo->mem->alloc_small)(
                        (j_common_ptr)cinfo, JPOOL_IMAGE,
                        cinfo->num_components * (SAVED_COEFS * SIZEOF(int)));
        coef_bits_latch = coef->coef_bits_latch;

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                /* All components' quantization values must already be latched. */
                if ((qtable = compptr->quant_table) == nullptr) return FALSE;
                /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide.
                 */
                if (qtable->quantval[0] == 0 || qtable->quantval[Q01_POS] == 0 ||
                        qtable->quantval[Q10_POS] == 0 || qtable->quantval[Q20_POS] == 0 ||
                        qtable->quantval[Q11_POS] == 0 || qtable->quantval[Q02_POS] == 0)
                        return FALSE;
                /* DC values must be at least partly known for all components. */
                coef_bits = cinfo->coef_bits[ci];
                if (coef_bits[0] < 0) return FALSE;
                /* Block smoothing is helpful if some AC coefficients remain inaccurate.
                 */
                for (coefi = 1; coefi <= 5; coefi++)
                {
                        coef_bits_latch[coefi] = coef_bits[coefi];
                        if (coef_bits[coefi] != 0) smoothing_useful = TRUE;
                }
                coef_bits_latch += SAVED_COEFS;
        }

        return smoothing_useful;
}

/*
 * Variant of decompress_data for use when doing block smoothing.
 */

METHODDEF(int)
decompress_smooth_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
        my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
        JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
        JDIMENSION block_num, last_block_column;
        int ci, block_row, block_rows, access_rows;
        JBLOCKARRAY buffer;
        JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
        JSAMPARRAY output_ptr;
        JDIMENSION output_col;
        jpeg_component_info* compptr;
        inverse_DCT_method_ptr inverse_DCT;
        boolean first_row, last_row;
        JBLOCK workspace;
        int* coef_bits;
        JQUANT_TBL* quanttbl;
        INT32 Q00, Q01, Q02, Q10, Q11, Q20, num;
        int DC1, DC2, DC3, DC4, DC5, DC6, DC7, DC8, DC9;
        int Al, pred;

        /* Force some input to be done if we are getting ahead of the input. */
        while (cinfo->input_scan_number <= cinfo->output_scan_number &&
                   !cinfo->inputctl->eoi_reached)
        {
                if (cinfo->input_scan_number == cinfo->output_scan_number)
                {
                        /* If input is working on current scan, we ordinarily want it to
                         * have completed the current row.  But if input scan is DC,
                         * we want it to keep one row ahead so that next block row's DC
                         * values are up to date.
                         */
                        JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
                        if (cinfo->input_iMCU_row > cinfo->output_iMCU_row + delta) break;
                }
                if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
                        return JPEG_SUSPENDED;
        }

        /* OK, output from the virtual arrays. */
        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                /* Don't bother to IDCT an uninteresting component. */
                if (!compptr->component_needed) continue;
                /* Count non-dummy DCT block rows in this iMCU row. */
                if (cinfo->output_iMCU_row < last_iMCU_row)
                {
                        block_rows = compptr->v_samp_factor;
                        access_rows = block_rows * 2; /* this and next iMCU row */
                        last_row = FALSE;
                }
                else
                {
                        /* NB: can't use last_row_height here; it is input-side-dependent!
                         */
                        block_rows =
                                (int)(compptr->height_in_blocks % compptr->v_samp_factor);
                        if (block_rows == 0) block_rows = compptr->v_samp_factor;
                        access_rows = block_rows; /* this iMCU row only */
                        last_row = TRUE;
                }
                /* Align the virtual buffer for this component. */
                if (cinfo->output_iMCU_row > 0)
                {
                        access_rows += compptr->v_samp_factor; /* prior iMCU row too */
                        buffer = (*cinfo->mem->access_virt_barray)(
                                (j_common_ptr)cinfo, coef->whole_image[ci],
                                (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
                                (JDIMENSION)access_rows, FALSE);
                        buffer += compptr->v_samp_factor; /* point to current iMCU row */
                        first_row = FALSE;
                }
                else
                {
                        buffer = (*cinfo->mem->access_virt_barray)(
                                (j_common_ptr)cinfo, coef->whole_image[ci], (JDIMENSION)0,
                                (JDIMENSION)access_rows, FALSE);
                        first_row = TRUE;
                }
                /* Fetch component-dependent info */
                coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
                quanttbl = compptr->quant_table;
                Q00 = quanttbl->quantval[0];
                Q01 = quanttbl->quantval[Q01_POS];
                Q10 = quanttbl->quantval[Q10_POS];
                Q20 = quanttbl->quantval[Q20_POS];
                Q11 = quanttbl->quantval[Q11_POS];
                Q02 = quanttbl->quantval[Q02_POS];
                inverse_DCT = cinfo->idct->inverse_DCT[ci];
                output_ptr = output_buf[ci];
                /* Loop over all DCT blocks to be processed. */
                for (block_row = 0; block_row < block_rows; block_row++)
                {
                        buffer_ptr = buffer[block_row];
                        if (first_row && block_row == 0)
                                prev_block_row = buffer_ptr;
                        else
                                prev_block_row = buffer[block_row - 1];
                        if (last_row && block_row == block_rows - 1)
                                next_block_row = buffer_ptr;
                        else
                                next_block_row = buffer[block_row + 1];
                        /* We fetch the surrounding DC values using a sliding-register
                         * approach.
                         * Initialize all nine here so as to do the right thing on narrow
                         * pics.
                         */
                        DC1 = DC2 = DC3 = (int)prev_block_row[0][0];
                        DC4 = DC5 = DC6 = (int)buffer_ptr[0][0];
                        DC7 = DC8 = DC9 = (int)next_block_row[0][0];
                        output_col = 0;
                        last_block_column = compptr->width_in_blocks - 1;
                        for (block_num = 0; block_num <= last_block_column; block_num++)
                        {
                                /* Fetch current DCT block into workspace so we can modify it.
                                 */
                                jcopy_block_row(
                                        buffer_ptr, (JBLOCKROW)workspace, (JDIMENSION)1);
                                /* Update DC values */
                                if (block_num < last_block_column)
                                {
                                        DC3 = (int)prev_block_row[1][0];
                                        DC6 = (int)buffer_ptr[1][0];
                                        DC9 = (int)next_block_row[1][0];
                                }
                                /* Compute coefficient estimates per K.8.
                                 * An estimate is applied only if coefficient is still zero,
                                 * and is not known to be fully accurate.
                                 */
                                /* AC01 */
                                if ((Al = coef_bits[1]) != 0 && workspace[1] == 0)
                                {
                                        num = 36 * Q00 * (DC4 - DC6);
                                        if (num >= 0)
                                        {
                                                pred = (int)(((Q01 << 7) + num) / (Q01 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                        }
                                        else
                                        {
                                                pred = (int)(((Q01 << 7) - num) / (Q01 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                                pred = -pred;
                                        }
                                        workspace[1] = (JCOEF)pred;
                                }
                                /* AC10 */
                                if ((Al = coef_bits[2]) != 0 && workspace[8] == 0)
                                {
                                        num = 36 * Q00 * (DC2 - DC8);
                                        if (num >= 0)
                                        {
                                                pred = (int)(((Q10 << 7) + num) / (Q10 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                        }
                                        else
                                        {
                                                pred = (int)(((Q10 << 7) - num) / (Q10 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                                pred = -pred;
                                        }
                                        workspace[8] = (JCOEF)pred;
                                }
                                /* AC20 */
                                if ((Al = coef_bits[3]) != 0 && workspace[16] == 0)
                                {
                                        num = 9 * Q00 * (DC2 + DC8 - 2 * DC5);
                                        if (num >= 0)
                                        {
                                                pred = (int)(((Q20 << 7) + num) / (Q20 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                        }
                                        else
                                        {
                                                pred = (int)(((Q20 << 7) - num) / (Q20 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                                pred = -pred;
                                        }
                                        workspace[16] = (JCOEF)pred;
                                }
                                /* AC11 */
                                if ((Al = coef_bits[4]) != 0 && workspace[9] == 0)
                                {
                                        num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
                                        if (num >= 0)
                                        {
                                                pred = (int)(((Q11 << 7) + num) / (Q11 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                        }
                                        else
                                        {
                                                pred = (int)(((Q11 << 7) - num) / (Q11 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                                pred = -pred;
                                        }
                                        workspace[9] = (JCOEF)pred;
                                }
                                /* AC02 */
                                if ((Al = coef_bits[5]) != 0 && workspace[2] == 0)
                                {
                                        num = 9 * Q00 * (DC4 + DC6 - 2 * DC5);
                                        if (num >= 0)
                                        {
                                                pred = (int)(((Q02 << 7) + num) / (Q02 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                        }
                                        else
                                        {
                                                pred = (int)(((Q02 << 7) - num) / (Q02 << 8));
                                                if (Al > 0 && pred >= (1 << Al)) pred = (1 << Al) - 1;
                                                pred = -pred;
                                        }
                                        workspace[2] = (JCOEF)pred;
                                }
                                /* OK, do the IDCT */
                                (*inverse_DCT)(
                                        cinfo, compptr, (JCOEFPTR)workspace, output_ptr,
                                        output_col);
                                /* Advance for next column */
                                DC1 = DC2;
                                DC2 = DC3;
                                DC4 = DC5;
                                DC5 = DC6;
                                DC7 = DC8;
                                DC8 = DC9;
                                buffer_ptr++, prev_block_row++, next_block_row++;
                                output_col += compptr->DCT_scaled_size;
                        }
                        output_ptr += compptr->DCT_scaled_size;
                }
        }

        if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
                return JPEG_ROW_COMPLETED;
        return JPEG_SCAN_COMPLETED;
}

#endif /* BLOCK_SMOOTHING_SUPPORTED */

/*
 * Initialize coefficient buffer controller.
 */

GLOBAL(void)
jinit_d_coef_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
{
        my_coef_ptr coef;

        coef = (my_coef_ptr)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_IMAGE, SIZEOF(my_coef_controller));
        cinfo->coef = (struct jpeg_d_coef_controller*)coef;
        coef->pub.start_input_pass = start_input_pass;
        coef->pub.start_output_pass = start_output_pass;
#ifdef BLOCK_SMOOTHING_SUPPORTED
        coef->coef_bits_latch = nullptr;
#endif

        /* Create the coefficient buffer. */
        if (need_full_buffer)
        {
#ifdef D_MULTISCAN_FILES_SUPPORTED
                /* Allocate a full-image virtual array for each component, */
                /* padded to a multiple of samp_factor DCT blocks in each direction. */
                /* Note we ask for a pre-zeroed array. */
                int ci, access_rows;
                jpeg_component_info* compptr;

                for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                         ci++, compptr++)
                {
                        access_rows = compptr->v_samp_factor;
#ifdef BLOCK_SMOOTHING_SUPPORTED
                        /* If block smoothing could be used, need a bigger window */
                        if (cinfo->progressive_mode) access_rows *= 3;
#endif
                        coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)(
                                (j_common_ptr)cinfo, JPOOL_IMAGE, TRUE,
                                (JDIMENSION)jround_up(
                                        (long)compptr->width_in_blocks,
                                        (long)compptr->h_samp_factor),
                                (JDIMENSION)jround_up(
                                        (long)compptr->height_in_blocks,
                                        (long)compptr->v_samp_factor),
                                (JDIMENSION)access_rows);
                }
                coef->pub.consume_data = consume_data;
                coef->pub.decompress_data = decompress_data;
                coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
#else
                ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
        }
        else
        {
                /* We only need a single-MCU buffer. */
                JBLOCKROW buffer;
                int i;

                buffer = (JBLOCKROW)(*cinfo->mem->alloc_large)(
                        (j_common_ptr)cinfo, JPOOL_IMAGE,
                        D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
                for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++)
                {
                        coef->MCU_buffer[i] = buffer + i;
                }
                coef->pub.consume_data = dummy_consume_data;
                coef->pub.decompress_data = decompress_onepass;
                coef->pub.coef_arrays = nullptr; /* flag for no virtual arrays */
        }
}