jcsample.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"

/* Pointer to routine to downsample a single component */
typedef JMETHOD(
        void, downsample1_ptr, (j_compress_ptr cinfo, jpeg_component_info* compptr,
                                                        JSAMPARRAY input_data, JSAMPARRAY output_data));

/* Private subobject */

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

        /* Downsampling method pointers, one per component */
        downsample1_ptr methods[MAX_COMPONENTS];
} my_downsampler;

typedef my_downsampler* my_downsample_ptr;

/*
 * Initialize for a downsampling pass.
 */

METHODDEF(void)
start_pass_downsample(j_compress_ptr) { /* no work for now */}
/*
 * Expand a component horizontally from width input_cols to width output_cols,
 * by duplicating the rightmost samples.
 */

LOCAL(void)
expand_right_edge(
        JSAMPARRAY image_data, int num_rows, JDIMENSION input_cols,
        JDIMENSION output_cols)
{
        JSAMPROW ptr;
        JSAMPLE pixval;
        int count;
        int row;
        int numcols = (int)(output_cols - input_cols);

        if (numcols > 0)
        {
                for (row = 0; row < num_rows; row++)
                {
                        ptr = image_data[row] + input_cols;
                        pixval = ptr[-1]; /* don't need GETJSAMPLE() here */
                        for (count = numcols; count > 0; count--) *ptr++ = pixval;
                }
        }
}

/*
 * Do downsampling for a whole row group (all components).
 *
 * In this version we simply downsample each component independently.
 */

METHODDEF(void)
sep_downsample(
        j_compress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION in_row_index,
        JSAMPIMAGE output_buf, JDIMENSION out_row_group_index)
{
        my_downsample_ptr downsample = (my_downsample_ptr)cinfo->downsample;
        int ci;
        jpeg_component_info* compptr;
        JSAMPARRAY in_ptr, out_ptr;

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                in_ptr = input_buf[ci] + in_row_index;
                out_ptr =
                        output_buf[ci] + (out_row_group_index * compptr->v_samp_factor);
                (*downsample->methods[ci])(cinfo, compptr, in_ptr, out_ptr);
        }
}

/*
 * Downsample pixel values of a single component.
 * One row group is processed per call.
 * This version handles arbitrary integral sampling ratios, without smoothing.
 * Note that this version is not actually used for customary sampling ratios.
 */

METHODDEF(void)
int_downsample(
        j_compress_ptr cinfo, jpeg_component_info* compptr, JSAMPARRAY input_data,
        JSAMPARRAY output_data)
{
        int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
        JDIMENSION outcol, outcol_h; /* outcol_h == outcol*h_expand */
        JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
        JSAMPROW inptr, outptr;
        INT32 outvalue;

        h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
        v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
        numpix = h_expand * v_expand;
        numpix2 = numpix / 2;

        /* Expand input data enough to let all the output samples be generated
         * by the standard loop.  Special-casing padded output would be more
         * efficient.
         */
        expand_right_edge(
                input_data, cinfo->max_v_samp_factor, cinfo->image_width,
                output_cols * h_expand);

        inrow = 0;
        for (outrow = 0; outrow < compptr->v_samp_factor; outrow++)
        {
                outptr = output_data[outrow];
                for (outcol = 0, outcol_h = 0; outcol < output_cols;
                         outcol++, outcol_h += h_expand)
                {
                        outvalue = 0;
                        for (v = 0; v < v_expand; v++)
                        {
                                inptr = input_data[inrow + v] + outcol_h;
                                for (h = 0; h < h_expand; h++)
                                {
                                        outvalue += (INT32)GETJSAMPLE(*inptr++);
                                }
                        }
                        *outptr++ = (JSAMPLE)((outvalue + numpix2) / numpix);
                }
                inrow += v_expand;
        }
}

/*
 * Downsample pixel values of a single component.
 * This version handles the special case of a full-size component,
 * without smoothing.
 */

METHODDEF(void)
fullsize_downsample(
        j_compress_ptr cinfo, jpeg_component_info* compptr, JSAMPARRAY input_data,
        JSAMPARRAY output_data)
{
        /* Copy the data */
        jcopy_sample_rows(
                input_data, 0, output_data, 0, cinfo->max_v_samp_factor,
                cinfo->image_width);
        /* Edge-expand */
        expand_right_edge(
                output_data, cinfo->max_v_samp_factor, cinfo->image_width,
                compptr->width_in_blocks * DCTSIZE);
}

/*
 * Downsample pixel values of a single component.
 * This version handles the common case of 2:1 horizontal and 1:1 vertical,
 * without smoothing.
 *
 * A note about the "bias" calculations: when rounding fractional values to
 * integer, we do not want to always round 0.5 up to the next integer.
 * If we did that, we'd introduce a noticeable bias towards larger values.
 * Instead, this code is arranged so that 0.5 will be rounded up or down at
 * alternate pixel locations (a simple ordered dither pattern).
 */

METHODDEF(void)
h2v1_downsample(
        j_compress_ptr cinfo, jpeg_component_info* compptr, JSAMPARRAY input_data,
        JSAMPARRAY output_data)
{
        int outrow;
        JDIMENSION outcol;
        JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
        JSAMPROW inptr, outptr;
        int bias;

        /* Expand input data enough to let all the output samples be generated
         * by the standard loop.  Special-casing padded output would be more
         * efficient.
         */
        expand_right_edge(
                input_data, cinfo->max_v_samp_factor, cinfo->image_width,
                output_cols * 2);

        for (outrow = 0; outrow < compptr->v_samp_factor; outrow++)
        {
                outptr = output_data[outrow];
                inptr = input_data[outrow];
                bias = 0; /* bias = 0,1,0,1,... for successive samples */
                for (outcol = 0; outcol < output_cols; outcol++)
                {
                        *outptr++ = (JSAMPLE)(
                                (GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1]) + bias) >> 1);
                        bias ^= 1; /* 0=>1, 1=>0 */
                        inptr += 2;
                }
        }
}

/*
 * Downsample pixel values of a single component.
 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
 * without smoothing.
 */

METHODDEF(void)
h2v2_downsample(
        j_compress_ptr cinfo, jpeg_component_info* compptr, JSAMPARRAY input_data,
        JSAMPARRAY output_data)
{
        int inrow, outrow;
        JDIMENSION outcol;
        JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
        JSAMPROW inptr0, inptr1, outptr;
        int bias;

        /* Expand input data enough to let all the output samples be generated
         * by the standard loop.  Special-casing padded output would be more
         * efficient.
         */
        expand_right_edge(
                input_data, cinfo->max_v_samp_factor, cinfo->image_width,
                output_cols * 2);

        inrow = 0;
        for (outrow = 0; outrow < compptr->v_samp_factor; outrow++)
        {
                outptr = output_data[outrow];
                inptr0 = input_data[inrow];
                inptr1 = input_data[inrow + 1];
                bias = 1; /* bias = 1,2,1,2,... for successive samples */
                for (outcol = 0; outcol < output_cols; outcol++)
                {
                        *outptr++ = (JSAMPLE)(
                                (GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
                                 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]) + bias) >>
                                2);
                        bias ^= 3; /* 1=>2, 2=>1 */
                        inptr0 += 2;
                        inptr1 += 2;
                }
                inrow += 2;
        }
}

#ifdef INPUT_SMOOTHING_SUPPORTED

/*
 * Downsample pixel values of a single component.
 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
 * with smoothing.  One row of context is required.
 */

METHODDEF(void)
h2v2_smooth_downsample(
        j_compress_ptr cinfo, jpeg_component_info* compptr, JSAMPARRAY input_data,
        JSAMPARRAY output_data)
{
        int inrow, outrow;
        JDIMENSION colctr;
        JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
        JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
        INT32 membersum, neighsum, memberscale, neighscale;

        /* Expand input data enough to let all the output samples be generated
         * by the standard loop.  Special-casing padded output would be more
         * efficient.
         */
        expand_right_edge(
                input_data - 1, cinfo->max_v_samp_factor + 2, cinfo->image_width,
                output_cols * 2);

        /* We don't bother to form the individual "smoothed" input pixel values;
         * we can directly compute the output which is the average of the four
         * smoothed values.  Each of the four member pixels contributes a fraction
         * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
         * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
         * output.  The four corner-adjacent neighbor pixels contribute a fraction
         * SF to just one smoothed pixel, or SF/4 to the final output; while the
         * eight edge-adjacent neighbors contribute SF to each of two smoothed
         * pixels, or SF/2 overall.  In order to use integer arithmetic, these
         * factors are scaled by 2^16 = 65536.
         * Also recall that SF = smoothing_factor / 1024.
         */

        memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
        neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */

        inrow = 0;
        for (outrow = 0; outrow < compptr->v_samp_factor; outrow++)
        {
                outptr = output_data[outrow];
                inptr0 = input_data[inrow];
                inptr1 = input_data[inrow + 1];
                above_ptr = input_data[inrow - 1];
                below_ptr = input_data[inrow + 2];

                /* Special case for first column: pretend column -1 is same as column 0
                 */
                membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
                                        GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
                neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
                                   GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
                                   GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
                                   GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
                neighsum += neighsum;
                neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
                                        GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
                membersum = membersum * memberscale + neighsum * neighscale;
                *outptr++ = (JSAMPLE)((membersum + 32768) >> 16);
                inptr0 += 2;
                inptr1 += 2;
                above_ptr += 2;
                below_ptr += 2;

                for (colctr = output_cols - 2; colctr > 0; colctr--)
                {
                        /* sum of pixels directly mapped to this output element */
                        membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
                                                GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
                        /* sum of edge-neighbor pixels */
                        neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
                                           GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
                                           GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
                                           GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
                        /* The edge-neighbors count twice as much as corner-neighbors */
                        neighsum += neighsum;
                        /* Add in the corner-neighbors */
                        neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
                                                GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
                        /* form final output scaled up by 2^16 */
                        membersum = membersum * memberscale + neighsum * neighscale;
                        /* round, descale and output it */
                        *outptr++ = (JSAMPLE)((membersum + 32768) >> 16);
                        inptr0 += 2;
                        inptr1 += 2;
                        above_ptr += 2;
                        below_ptr += 2;
                }

                /* Special case for last column */
                membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
                                        GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
                neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
                                   GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
                                   GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
                                   GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
                neighsum += neighsum;
                neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
                                        GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
                membersum = membersum * memberscale + neighsum * neighscale;
                *outptr = (JSAMPLE)((membersum + 32768) >> 16);

                inrow += 2;
        }
}

/*
 * Downsample pixel values of a single component.
 * This version handles the special case of a full-size component,
 * with smoothing.  One row of context is required.
 */

METHODDEF(void)
fullsize_smooth_downsample(
        j_compress_ptr cinfo, jpeg_component_info* compptr, JSAMPARRAY input_data,
        JSAMPARRAY output_data)
{
        int outrow;
        JDIMENSION colctr;
        JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
        JSAMPROW inptr, above_ptr, below_ptr, outptr;
        INT32 membersum, neighsum, memberscale, neighscale;
        int colsum, lastcolsum, nextcolsum;

        /* Expand input data enough to let all the output samples be generated
         * by the standard loop.  Special-casing padded output would be more
         * efficient.
         */
        expand_right_edge(
                input_data - 1, cinfo->max_v_samp_factor + 2, cinfo->image_width,
                output_cols);

        /* Each of the eight neighbor pixels contributes a fraction SF to the
         * smoothed pixel, while the main pixel contributes (1-8*SF).  In order
         * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
         * Also recall that SF = smoothing_factor / 1024.
         */

        memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
        neighscale = cinfo->smoothing_factor * 64; /* scaled SF */

        for (outrow = 0; outrow < compptr->v_samp_factor; outrow++)
        {
                outptr = output_data[outrow];
                inptr = input_data[outrow];
                above_ptr = input_data[outrow - 1];
                below_ptr = input_data[outrow + 1];

                /* Special case for first column */
                colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
                                 GETJSAMPLE(*inptr);
                membersum = GETJSAMPLE(*inptr++);
                nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
                                         GETJSAMPLE(*inptr);
                neighsum = colsum + (colsum - membersum) + nextcolsum;
                membersum = membersum * memberscale + neighsum * neighscale;
                *outptr++ = (JSAMPLE)((membersum + 32768) >> 16);
                lastcolsum = colsum;
                colsum = nextcolsum;

                for (colctr = output_cols - 2; colctr > 0; colctr--)
                {
                        membersum = GETJSAMPLE(*inptr++);
                        above_ptr++;
                        below_ptr++;
                        nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
                                                 GETJSAMPLE(*inptr);
                        neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
                        membersum = membersum * memberscale + neighsum * neighscale;
                        *outptr++ = (JSAMPLE)((membersum + 32768) >> 16);
                        lastcolsum = colsum;
                        colsum = nextcolsum;
                }

                /* Special case for last column */
                membersum = GETJSAMPLE(*inptr);
                neighsum = lastcolsum + (colsum - membersum) + colsum;
                membersum = membersum * memberscale + neighsum * neighscale;
                *outptr = (JSAMPLE)((membersum + 32768) >> 16);
        }
}

#endif /* INPUT_SMOOTHING_SUPPORTED */

/*
 * Module initialization routine for downsampling.
 * Note that we must select a routine for each component.
 */

GLOBAL(void)
jinit_downsampler(j_compress_ptr cinfo)
{
        my_downsample_ptr downsample;
        int ci;
        jpeg_component_info* compptr;
        boolean smoothok = TRUE;

        downsample = (my_downsample_ptr)(*cinfo->mem->alloc_small)(
                (j_common_ptr)cinfo, JPOOL_IMAGE, SIZEOF(my_downsampler));
        cinfo->downsample = (struct jpeg_downsampler*)downsample;
        downsample->pub.start_pass = start_pass_downsample;
        downsample->pub.downsample = sep_downsample;
        downsample->pub.need_context_rows = FALSE;

        if (cinfo->CCIR601_sampling) ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

        /* Verify we can handle the sampling factors, and set up method pointers */
        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
                 ci++, compptr++)
        {
                if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
                        compptr->v_samp_factor == cinfo->max_v_samp_factor)
                {
#ifdef INPUT_SMOOTHING_SUPPORTED
                        if (cinfo->smoothing_factor)
                        {
                                downsample->methods[ci] = fullsize_smooth_downsample;
                                downsample->pub.need_context_rows = TRUE;
                        }
                        else
#endif
                                downsample->methods[ci] = fullsize_downsample;
                }
                else if (
                        compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
                        compptr->v_samp_factor == cinfo->max_v_samp_factor)
                {
                        smoothok = FALSE;
                        downsample->methods[ci] = h2v1_downsample;
                }
                else if (
                        compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
                        compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor)
                {
#ifdef INPUT_SMOOTHING_SUPPORTED
                        if (cinfo->smoothing_factor)
                        {
                                downsample->methods[ci] = h2v2_smooth_downsample;
                                downsample->pub.need_context_rows = TRUE;
                        }
                        else
#endif
                                downsample->methods[ci] = h2v2_downsample;
                }
                else if (
                        (cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
                        (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
                {
                        smoothok = FALSE;
                        downsample->methods[ci] = int_downsample;
                }
                else
                        ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
        }

#ifdef INPUT_SMOOTHING_SUPPORTED
        if (cinfo->smoothing_factor && !smoothok)
                TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);
#endif
}