/*

 * jdscale.c

 *

 * Copyright (C) 1998, 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 sample scaling for lossless JPEG.  This is a

 * combination of upscaling the undifferenced sample by 2^Pt and downscaling

 * the sample to fit into JSAMPLE.

 */

#define JPEG_INTERNALS

#include "jinclude16.h"

#include "jpeglib16.h"

#include "jlossls16.h"    /* Private declarations for lossless codec */

#ifdef D_LOSSLESS_SUPPORTED

/*

 * Private scaler object for lossless decoding.

 */

typedef struct {

  int scale_factor;

} scaler;

typedef scaler * scaler_ptr;

/*

 * Scalers for packing sample differences into JSAMPLEs.

 */

METHODDEF(void)

simple_upscale(j_decompress_ptr cinfo,

         const JDIFFROW diff_buf, JSAMPROW output_buf,

         JDIMENSION width)

{

  j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;

  scaler_ptr scale = (scaler_ptr) losslsd->scaler_private;

  int scale_factor = scale->scale_factor;

  unsigned int xindex;

  for (xindex = 0; xindex < width; xindex++)

    output_buf[xindex] = (JSAMPLE) (diff_buf[xindex] << scale_factor);

}

METHODDEF(void)

simple_downscale(j_decompress_ptr cinfo,

     const JDIFFROW diff_buf, JSAMPROW output_buf,

     JDIMENSION width)

{

  j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;

  scaler_ptr scale = (scaler_ptr) losslsd->scaler_private;

  int scale_factor = scale->scale_factor;

  unsigned int xindex;

  SHIFT_TEMPS

  for (xindex = 0; xindex < width; xindex++)

    output_buf[xindex] = (JSAMPLE) RIGHT_SHIFT(diff_buf[xindex], scale_factor);

}

METHODDEF(void)

noscale(j_decompress_ptr cinfo,

  const JDIFFROW diff_buf, JSAMPROW output_buf,

  JDIMENSION width)

{

  (void)cinfo;

  unsigned int xindex;

  for (xindex = 0; xindex < width; xindex++)

    output_buf[xindex] = (JSAMPLE) diff_buf[xindex];

}

METHODDEF(void)

scaler_start_pass (j_decompress_ptr cinfo)

{

  j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;

  scaler_ptr scale = (scaler_ptr) losslsd->scaler_private;

  int downscale;

  /*

   * Downscale by the difference in the input vs. output precision.  If the

   * output precision >= input precision, then do not downscale.

   */

  downscale = BITS_IN_JSAMPLE < cinfo->data_precision ?

    cinfo->data_precision - BITS_IN_JSAMPLE : 0;

  scale->scale_factor = cinfo->Al - downscale;

  /* Set scaler functions based on scale_factor (positive = left shift) */

  if (scale->scale_factor > 0)

    losslsd->scaler_scale = simple_upscale;

  else if (scale->scale_factor < 0) {

    scale->scale_factor = -scale->scale_factor;

    losslsd->scaler_scale = simple_downscale;

  }

  else

    losslsd->scaler_scale = noscale;

}

GLOBAL(void)

jinit_d_scaler (j_decompress_ptr cinfo)

{

  j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;

  scaler_ptr scale;

  scale = (scaler_ptr)

    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

        SIZEOF(scaler));

  losslsd->scaler_private = (void *) scale;

  losslsd->scaler_start_pass = scaler_start_pass;

}

#endif /* D_LOSSLESS_SUPPORTED */