/*
 * jdmerge.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains code for merged upsampling/color conversion.
 *
 * This file combines functions from jdsample.c and jdcolor.c;
 * read those files first to understand what's going on.
 *
 * When the chroma components are to be upsampled by simple replication
 * (ie, box filtering), we can save some work in color conversion by
 * calculating all the output pixels corresponding to a pair of chroma
 * samples at one time.  In the conversion equations
 *	R = Y           + K1 * Cr
 *	G = Y + K2 * Cb + K3 * Cr
 *	B = Y + K4 * Cb
 * only the Y term varies among the group of pixels corresponding to a pair
 * of chroma samples, so the rest of the terms can be calculated just once.
 * At typical sampling ratios, this eliminates half or three-quarters of the
 * multiplications needed for color conversion.
 *
 * This file currently provides implementations for the following cases:
 *	YCbCr => RGB color conversion only.
 *	Sampling ratios of 2h1v or 2h2v.
 *	No scaling needed at upsample time.
 *	Corner-aligned (non-CCIR601) sampling alignment.
 * Other special cases could be added, but in most applications these are
 * the only common cases.  (For uncommon cases we fall back on the more
 * general code in jdsample.c and jdcolor.c.)
 */

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

#ifdef UPSAMPLE_MERGING_SUPPORTED


/* Private subobject */

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

    /* Pointer to routine to do actual upsampling/conversion of one row group */
    JMETHOD(void, upmethod, (j_decompress_ptr cinfo,
                             JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
                             JSAMPARRAY output_buf));

    /* Private state for YCC->RGB conversion */
    int * Cr_r_tab;		/* => table for Cr to R conversion */
    int * Cb_b_tab;		/* => table for Cb to B conversion */
    INT32 * Cr_g_tab;		/* => table for Cr to G conversion */
    INT32 * Cb_g_tab;		/* => table for Cb to G conversion */

    /* For 2:1 vertical sampling, we produce two output rows at a time.
     * We need a "spare" row buffer to hold the second output row if the
     * application provides just a one-row buffer; we also use the spare
     * to discard the dummy last row if the image height is odd.
     */
    JSAMPROW spare_row;
    boolean spare_full;		/* T if spare buffer is occupied */

    JDIMENSION out_row_width;	/* samples per output row */
    JDIMENSION rows_to_go;	/* counts rows remaining in image */
} my_upsampler;

typedef my_upsampler * my_upsample_ptr;

#define SCALEBITS	16	/* speediest right-shift on some machines */
#define ONE_HALF	((INT32) 1 << (SCALEBITS-1))
#define FIX(x)		((INT32) ((x) * (1L<<SCALEBITS) + 0.5))


/*
 * Initialize tables for YCC->RGB colorspace conversion.
 * This is taken directly from jdcolor.c; see that file for more info.
 */

LOCAL(void)
build_ycc_rgb_table (j_decompress_ptr cinfo)
{
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    int i;
    INT32 x;
    SHIFT_TEMPS

    upsample->Cr_r_tab = (int *)
                         (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                 (MAXJSAMPLE+1) * SIZEOF(int));
    upsample->Cb_b_tab = (int *)
                         (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                 (MAXJSAMPLE+1) * SIZEOF(int));
    upsample->Cr_g_tab = (INT32 *)
                         (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                 (MAXJSAMPLE+1) * SIZEOF(INT32));
    upsample->Cb_g_tab = (INT32 *)
                         (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                 (MAXJSAMPLE+1) * SIZEOF(INT32));

    for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++)
    {
        /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
        /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
        /* Cr=>R value is nearest int to 1.40200 * x */
        upsample->Cr_r_tab[i] = (int)
                                RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
        /* Cb=>B value is nearest int to 1.77200 * x */
        upsample->Cb_b_tab[i] = (int)
                                RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
        /* Cr=>G value is scaled-up -0.71414 * x */
        upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x;
        /* Cb=>G value is scaled-up -0.34414 * x */
        /* We also add in ONE_HALF so that need not do it in inner loop */
        upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
    }
}


/*
 * Initialize for an upsampling pass.
 */

METHODDEF(void)
start_pass_merged_upsample (j_decompress_ptr cinfo)
{
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

    /* Mark the spare buffer empty */
    upsample->spare_full = FALSE;
    /* Initialize total-height counter for detecting bottom of image */
    upsample->rows_to_go = cinfo->output_height;
}


/*
 * Control routine to do upsampling (and color conversion).
 *
 * The control routine just handles the row buffering considerations.
 */

METHODDEF(void)
merged_2v_upsample (j_decompress_ptr cinfo,
                    JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
                    JDIMENSION in_row_groups_avail,
                    JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
                    JDIMENSION out_rows_avail)
/* 2:1 vertical sampling case: may need a spare row. */
{
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    JSAMPROW work_ptrs[2];
    JDIMENSION num_rows;		/* number of rows returned to caller */

    if (upsample->spare_full)
    {
        /* If we have a spare row saved from a previous cycle, just return it. */
        jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
                          1, upsample->out_row_width);
        num_rows = 1;
        upsample->spare_full = FALSE;
    }
    else
    {
        /* Figure number of rows to return to caller. */
        num_rows = 2;
        /* Not more than the distance to the end of the image. */
        if (num_rows > upsample->rows_to_go)
        {
            num_rows = upsample->rows_to_go;
        }
        /* And not more than what the client can accept: */
        out_rows_avail -= *out_row_ctr;
        if (num_rows > out_rows_avail)
        {
            num_rows = out_rows_avail;
        }
        /* Create output pointer array for upsampler. */
        work_ptrs[0] = output_buf[*out_row_ctr];
        if (num_rows > 1)
        {
            work_ptrs[1] = output_buf[*out_row_ctr + 1];
        }
        else
        {
            work_ptrs[1] = upsample->spare_row;
            upsample->spare_full = TRUE;
        }
        /* Now do the upsampling. */
        (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
    }

    /* Adjust counts */
    *out_row_ctr += num_rows;
    upsample->rows_to_go -= num_rows;
    /* When the buffer is emptied, declare this input row group consumed */
    if (! upsample->spare_full)
    {
        (*in_row_group_ctr)++;
    }
}


METHODDEF(void)
merged_1v_upsample (j_decompress_ptr cinfo,
                    JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
                    JDIMENSION in_row_groups_avail,
                    JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
                    JDIMENSION out_rows_avail)
/* 1:1 vertical sampling case: much easier, never need a spare row. */
{
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

    /* Just do the upsampling. */
    (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
                           output_buf + *out_row_ctr);
    /* Adjust counts */
    (*out_row_ctr)++;
    (*in_row_group_ctr)++;
}


/*
 * These are the routines invoked by the control routines to do
 * the actual upsampling/conversion.  One row group is processed per call.
 *
 * Note: since we may be writing directly into application-supplied buffers,
 * we have to be honest about the output width; we can't assume the buffer
 * has been rounded up to an even width.
 */


/*
 * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
 */

METHODDEF(void)
h2v1_merged_upsample (j_decompress_ptr cinfo,
                      JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
                      JSAMPARRAY output_buf)
{
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    register int y, cred, cgreen, cblue;
    int cb, cr;
    register JSAMPROW outptr;
    JSAMPROW inptr0, inptr1, inptr2;
    JDIMENSION col;
    /* copy these pointers into registers if possible */
    register JSAMPLE * range_limit = cinfo->sample_range_limit;
    int * Crrtab = upsample->Cr_r_tab;
    int * Cbbtab = upsample->Cb_b_tab;
    INT32 * Crgtab = upsample->Cr_g_tab;
    INT32 * Cbgtab = upsample->Cb_g_tab;
    SHIFT_TEMPS

    inptr0 = input_buf[0][in_row_group_ctr];
    inptr1 = input_buf[1][in_row_group_ctr];
    inptr2 = input_buf[2][in_row_group_ctr];
    outptr = output_buf[0];
    /* Loop for each pair of output pixels */
    for (col = cinfo->output_width >> 1; col > 0; col--)
    {
        /* Do the chroma part of the calculation */
        cb = GETJSAMPLE(*inptr1++);
        cr = GETJSAMPLE(*inptr2++);
        cred = Crrtab[cr];
        cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
        cblue = Cbbtab[cb];
        /* Fetch 2 Y values and emit 2 pixels */
        y  = GETJSAMPLE(*inptr0++);
        outptr[RGB_RED] =   range_limit[y + cred];
        outptr[RGB_GREEN] = range_limit[y + cgreen];
        outptr[RGB_BLUE] =  range_limit[y + cblue];
        outptr += RGB_PIXELSIZE;
        y  = GETJSAMPLE(*inptr0++);
        outptr[RGB_RED] =   range_limit[y + cred];
        outptr[RGB_GREEN] = range_limit[y + cgreen];
        outptr[RGB_BLUE] =  range_limit[y + cblue];
        outptr += RGB_PIXELSIZE;
    }
    /* If image width is odd, do the last output column separately */
    if (cinfo->output_width & 1)
    {
        cb = GETJSAMPLE(*inptr1);
        cr = GETJSAMPLE(*inptr2);
        cred = Crrtab[cr];
        cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
        cblue = Cbbtab[cb];
        y  = GETJSAMPLE(*inptr0);
        outptr[RGB_RED] =   range_limit[y + cred];
        outptr[RGB_GREEN] = range_limit[y + cgreen];
        outptr[RGB_BLUE] =  range_limit[y + cblue];
    }
}


/*
 * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
 */

METHODDEF(void)
h2v2_merged_upsample (j_decompress_ptr cinfo,
                      JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
                      JSAMPARRAY output_buf)
{
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    register int y, cred, cgreen, cblue;
    int cb, cr;
    register JSAMPROW outptr0, outptr1;
    JSAMPROW inptr00, inptr01, inptr1, inptr2;
    JDIMENSION col;
    /* copy these pointers into registers if possible */
    register JSAMPLE * range_limit = cinfo->sample_range_limit;
    int * Crrtab = upsample->Cr_r_tab;
    int * Cbbtab = upsample->Cb_b_tab;
    INT32 * Crgtab = upsample->Cr_g_tab;
    INT32 * Cbgtab = upsample->Cb_g_tab;
    SHIFT_TEMPS

    inptr00 = input_buf[0][in_row_group_ctr*2];
    inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
    inptr1 = input_buf[1][in_row_group_ctr];
    inptr2 = input_buf[2][in_row_group_ctr];
    outptr0 = output_buf[0];
    outptr1 = output_buf[1];
    /* Loop for each group of output pixels */
    for (col = cinfo->output_width >> 1; col > 0; col--)
    {
        /* Do the chroma part of the calculation */
        cb = GETJSAMPLE(*inptr1++);
        cr = GETJSAMPLE(*inptr2++);
        cred = Crrtab[cr];
        cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
        cblue = Cbbtab[cb];
        /* Fetch 4 Y values and emit 4 pixels */
        y  = GETJSAMPLE(*inptr00++);
        outptr0[RGB_RED] =   range_limit[y + cred];
        outptr0[RGB_GREEN] = range_limit[y + cgreen];
        outptr0[RGB_BLUE] =  range_limit[y + cblue];
        outptr0 += RGB_PIXELSIZE;
        y  = GETJSAMPLE(*inptr00++);
        outptr0[RGB_RED] =   range_limit[y + cred];
        outptr0[RGB_GREEN] = range_limit[y + cgreen];
        outptr0[RGB_BLUE] =  range_limit[y + cblue];
        outptr0 += RGB_PIXELSIZE;
        y  = GETJSAMPLE(*inptr01++);
        outptr1[RGB_RED] =   range_limit[y + cred];
        outptr1[RGB_GREEN] = range_limit[y + cgreen];
        outptr1[RGB_BLUE] =  range_limit[y + cblue];
        outptr1 += RGB_PIXELSIZE;
        y  = GETJSAMPLE(*inptr01++);
        outptr1[RGB_RED] =   range_limit[y + cred];
        outptr1[RGB_GREEN] = range_limit[y + cgreen];
        outptr1[RGB_BLUE] =  range_limit[y + cblue];
        outptr1 += RGB_PIXELSIZE;
    }
    /* If image width is odd, do the last output column separately */
    if (cinfo->output_width & 1)
    {
        cb = GETJSAMPLE(*inptr1);
        cr = GETJSAMPLE(*inptr2);
        cred = Crrtab[cr];
        cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
        cblue = Cbbtab[cb];
        y  = GETJSAMPLE(*inptr00);
        outptr0[RGB_RED] =   range_limit[y + cred];
        outptr0[RGB_GREEN] = range_limit[y + cgreen];
        outptr0[RGB_BLUE] =  range_limit[y + cblue];
        y  = GETJSAMPLE(*inptr01);
        outptr1[RGB_RED] =   range_limit[y + cred];
        outptr1[RGB_GREEN] = range_limit[y + cgreen];
        outptr1[RGB_BLUE] =  range_limit[y + cblue];
    }
}


/*
 * Module initialization routine for merged upsampling/color conversion.
 *
 * NB: this is called under the conditions determined by use_merged_upsample()
 * in jdmaster.c.  That routine MUST correspond to the actual capabilities
 * of this module; no safety checks are made here.
 */

GLOBAL(void)
jinit_merged_upsampler (j_decompress_ptr cinfo)
{
    my_upsample_ptr upsample;

    upsample = (my_upsample_ptr)
               (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                           SIZEOF(my_upsampler));
    cinfo->upsample = (struct jpeg_upsampler *) upsample;
    upsample->pub.start_pass = start_pass_merged_upsample;
    upsample->pub.need_context_rows = FALSE;

    upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;

    if (cinfo->max_v_samp_factor == 2)
    {
        upsample->pub.upsample = merged_2v_upsample;
        upsample->upmethod = h2v2_merged_upsample;
        /* Allocate a spare row buffer */
        upsample->spare_row = (JSAMPROW)
                              (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                      (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
    }
    else
    {
        upsample->pub.upsample = merged_1v_upsample;
        upsample->upmethod = h2v1_merged_upsample;
        /* No spare row needed */
        upsample->spare_row = NULL;
    }

    build_ycc_rgb_table(cinfo);
}

#endif /* UPSAMPLE_MERGING_SUPPORTED */
