/*

 * jdsample.c

 *

 * Copyright (C) 1991-1996, 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 upsampling routines.

 *

 * Upsampling 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.  Upsampling will normally produce

 * max_v_samp_factor pixel rows from each row group (but this could vary

 * if the upsampler is applying a scale factor of its own).

 *

 * An excellent reference for image resampling is

 *   Digital Image Warping, George Wolberg, 1990.

 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.

 */

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

/* Pointer to routine to upsample a single component */

typedef JMETHOD(void, upsample1_ptr,

		(j_decompress_ptr cinfo, jpeg_component_info * compptr,

		 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));

/* Private subobject */

typedef struct {

  struct jpeg_upsampler pub;	/* public fields */

  /* Color conversion buffer.  When using separate upsampling and color

   * conversion steps, this buffer holds one upsampled row group until it

   * has been color converted and output.

   * Note: we do not allocate any storage for component(s) which are full-size,

   * ie do not need rescaling.  The corresponding entry of color_buf[] is

   * simply set to point to the input data array, thereby avoiding copying.

   */

  JSAMPARRAY color_buf[MAX_COMPONENTS];

  /* Per-component upsampling method pointers */

  upsample1_ptr methods[MAX_COMPONENTS];

  int next_row_out;		/* counts rows emitted from color_buf */

  JDIMENSION rows_to_go;	/* counts rows remaining in image */

  /* Height of an input row group for each component. */

  int rowgroup_height[MAX_COMPONENTS];

  /* These arrays save pixel expansion factors so that int_expand need not

   * recompute them each time.  They are unused for other upsampling methods.

   */

  UINT8 h_expand[MAX_COMPONENTS];

  UINT8 v_expand[MAX_COMPONENTS];

} my_upsampler;

typedef my_upsampler * my_upsample_ptr;

/*

 * Initialize for an upsampling pass.

 */

METHODDEF(void)

start_pass_upsample (j_decompress_ptr cinfo)

{

  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

  /* Mark the conversion buffer empty */

  upsample->next_row_out = cinfo->max_v_samp_factor;

  /* Initialize total-height counter for detecting bottom of image */

  upsample->rows_to_go = cinfo->output_height;

}

/*

 * Control routine to do upsampling (and color conversion).

 *

 * In this version we upsample each component independently.

 * We upsample one row group into the conversion buffer, then apply

 * color conversion a row at a time.

 */

METHODDEF(void)

sep_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)

{

  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

  int ci;

  jpeg_component_info * compptr;

  JDIMENSION num_rows;

  /* Fill the conversion buffer, if it's empty */

  if (upsample->next_row_out >= cinfo->max_v_samp_factor) {

    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

	 ci++, compptr++) {

      /* Invoke per-component upsample method.  Notice we pass a POINTER

       * to color_buf[ci], so that fullsize_upsample can change it.

       */

      (*upsample->methods[ci]) (cinfo, compptr,

	input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),

	upsample->color_buf + ci);

    }

    upsample->next_row_out = 0;

  }

  /* Color-convert and emit rows */

  /* How many we have in the buffer: */

  num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);

  /* Not more than the distance to the end of the image.  Need this test

   * in case the image height is not a multiple of max_v_samp_factor:

   */

  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;

  (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,

				     (JDIMENSION) upsample->next_row_out,

				     output_buf + *out_row_ctr,

				     (int) num_rows);

  /* Adjust counts */

  *out_row_ctr += num_rows;

  upsample->rows_to_go -= num_rows;

  upsample->next_row_out += num_rows;

  /* When the buffer is emptied, declare this input row group consumed */

  if (upsample->next_row_out >= cinfo->max_v_samp_factor)

    (*in_row_group_ctr)++;

}

/*

 * These are the routines invoked by sep_upsample to upsample pixel values

 * of a single component.  One row group is processed per call.

 */

/*

 * For full-size components, we just make color_buf[ci] point at the

 * input buffer, and thus avoid copying any data.  Note that this is

 * safe only because sep_upsample doesn't declare the input row group

 * "consumed" until we are done color converting and emitting it.

 */

METHODDEF(void)

fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

		   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

{

  *output_data_ptr = input_data;

}

/*

 * This is a no-op version used for "uninteresting" components.

 * These components will not be referenced by color conversion.

 */

METHODDEF(void)

noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

{

  *output_data_ptr = NULL;	/* safety check */

}

/*

 * This version handles any integral sampling ratios.

 * This is not used for typical JPEG files, so it need not be fast.

 * Nor, for that matter, is it particularly accurate: the algorithm is

 * simple replication of the input pixel onto the corresponding output

 * pixels.  The hi-falutin sampling literature refers to this as a

 * "box filter".  A box filter tends to introduce visible artifacts,

 * so if you are actually going to use 3:1 or 4:1 sampling ratios

 * you would be well advised to improve this code.

 */

METHODDEF(void)

int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

	      JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

{

  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

  JSAMPARRAY output_data = *output_data_ptr;

  register JSAMPROW inptr, outptr;

  register JSAMPLE invalue;

  register int h;

  JSAMPROW outend;

  int h_expand, v_expand;

  int inrow, outrow;

  h_expand = upsample->h_expand[compptr->component_index];

  v_expand = upsample->v_expand[compptr->component_index];

  inrow = outrow = 0;

  while (outrow < cinfo->max_v_samp_factor) {

    /* Generate one output row with proper horizontal expansion */

    inptr = input_data[inrow];

    outptr = output_data[outrow];

    outend = outptr + cinfo->output_width;

    while (outptr < outend) {

      invalue = *inptr++;	/* don't need GETJSAMPLE() here */

      for (h = h_expand; h > 0; h--) {

	*outptr++ = invalue;

      }

    }

    /* Generate any additional output rows by duplicating the first one */

    if (v_expand > 1) {

      jcopy_sample_rows(output_data, outrow, output_data, outrow+1,

			v_expand-1, cinfo->output_width);

    }

    inrow++;

    outrow += v_expand;

  }

}

/*

 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.

 * It's still a box filter.

 */

METHODDEF(void)

h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

{

  JSAMPARRAY output_data = *output_data_ptr;

  register JSAMPROW inptr, outptr;

  register JSAMPLE invalue;

  JSAMPROW outend;

  int inrow;

  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {

    inptr = input_data[inrow];

    outptr = output_data[inrow];

    outend = outptr + cinfo->output_width;

    while (outptr < outend) {

      invalue = *inptr++;	/* don't need GETJSAMPLE() here */

      *outptr++ = invalue;

      *outptr++ = invalue;

    }

  }

}

/*

 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.

 * It's still a box filter.

 */

METHODDEF(void)

h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

{

  JSAMPARRAY output_data = *output_data_ptr;

  register JSAMPROW inptr, outptr;

  register JSAMPLE invalue;

  JSAMPROW outend;

  int inrow, outrow;

  inrow = outrow = 0;

  while (outrow < cinfo->max_v_samp_factor) {

    inptr = input_data[inrow];

    outptr = output_data[outrow];

    outend = outptr + cinfo->output_width;

    while (outptr < outend) {

      invalue = *inptr++;	/* don't need GETJSAMPLE() here */

      *outptr++ = invalue;

      *outptr++ = invalue;

    }

    jcopy_sample_rows(output_data, outrow, output_data, outrow+1,

		      1, cinfo->output_width);

    inrow++;

    outrow += 2;

  }

}

/*

 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.

 *

 * The upsampling algorithm is linear interpolation between pixel centers,

 * also known as a "triangle filter".  This is a good compromise between

 * speed and visual quality.  The centers of the output pixels are 1/4 and 3/4

 * of the way between input pixel centers.

 *

 * 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_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

		     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

{

  JSAMPARRAY output_data = *output_data_ptr;

  register JSAMPROW inptr, outptr;

  register int invalue;

  register JDIMENSION colctr;

  int inrow;

  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {

    inptr = input_data[inrow];

    outptr = output_data[inrow];

    /* Special case for first column */

    invalue = GETJSAMPLE(*inptr++);

    *outptr++ = (JSAMPLE) invalue;

    *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);

    for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {

      /* General case: 3/4 * nearer pixel + 1/4 * further pixel */

      invalue = GETJSAMPLE(*inptr++) * 3;

      *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);

      *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);

    }

    /* Special case for last column */

    invalue = GETJSAMPLE(*inptr);

    *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);

    *outptr++ = (JSAMPLE) invalue;

  }

}

/*

 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.

 * Again a triangle filter; see comments for h2v1 case, above.

 *

 * It is OK for us to reference the adjacent input rows because we demanded

 * context from the main buffer controller (see initialization code).

 */

METHODDEF(void)

h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,

		     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)

{

  JSAMPARRAY output_data = *output_data_ptr;

  register JSAMPROW inptr0, inptr1, outptr;

#if BITS_IN_JSAMPLE == 8

  register int thiscolsum, lastcolsum, nextcolsum;

#else

  register INT32 thiscolsum, lastcolsum, nextcolsum;

#endif

  register JDIMENSION colctr;

  int inrow, outrow, v;

  inrow = outrow = 0;

  while (outrow < cinfo->max_v_samp_factor) {

    for (v = 0; v < 2; v++) {

      /* inptr0 points to nearest input row, inptr1 points to next nearest */

      inptr0 = input_data[inrow];

      if (v == 0)		/* next nearest is row above */

	inptr1 = input_data[inrow-1];

      else			/* next nearest is row below */

	inptr1 = input_data[inrow+1];

      outptr = output_data[outrow++];

      /* Special case for first column */

      thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);

      nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);

      *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);

      *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);

      lastcolsum = thiscolsum; thiscolsum = nextcolsum;

      for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {

	/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */

	/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */

	nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);

	*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);

	*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);

	lastcolsum = thiscolsum; thiscolsum = nextcolsum;

      }

      /* Special case for last column */

      *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);

      *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);

    }

    inrow++;

  }

}

/*

 * Module initialization routine for upsampling.

 */

GLOBAL(void)

jinit_upsampler (j_decompress_ptr cinfo)

{

  my_upsample_ptr upsample;

  int ci;

  jpeg_component_info * compptr;

  boolean need_buffer, do_fancy;

  int h_in_group, v_in_group, h_out_group, v_out_group;

  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_upsample;

  upsample->pub.upsample = sep_upsample;

  upsample->pub.need_context_rows = FALSE; /* until we find out differently */

  if (cinfo->CCIR601_sampling)	/* this isn't supported */

    ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

  /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,

   * so don't ask for it.

   */

  do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;

  /* Verify we can handle the sampling factors, select per-component methods,

   * and create storage as needed.

   */

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

       ci++, compptr++) {

    /* Compute size of an "input group" after IDCT scaling.  This many samples

     * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.

     */

    h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) /

		 cinfo->min_DCT_scaled_size;

    v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) /

		 cinfo->min_DCT_scaled_size;

    h_out_group = cinfo->max_h_samp_factor;

    v_out_group = cinfo->max_v_samp_factor;

    upsample->rowgroup_height[ci] = v_in_group; /* save for use later */

    need_buffer = TRUE;

    if (! compptr->component_needed) {

      /* Don't bother to upsample an uninteresting component. */

      upsample->methods[ci] = noop_upsample;

      need_buffer = FALSE;

    } else if (h_in_group == h_out_group && v_in_group == v_out_group) {

      /* Fullsize components can be processed without any work. */

      upsample->methods[ci] = fullsize_upsample;

      need_buffer = FALSE;

    } else if (h_in_group * 2 == h_out_group &&

	       v_in_group == v_out_group) {

      /* Special cases for 2h1v upsampling */

      if (do_fancy && compptr->downsampled_width > 2)

	upsample->methods[ci] = h2v1_fancy_upsample;

      else

	upsample->methods[ci] = h2v1_upsample;

    } else if (h_in_group * 2 == h_out_group &&

	       v_in_group * 2 == v_out_group) {

      /* Special cases for 2h2v upsampling */

      if (do_fancy && compptr->downsampled_width > 2) {

	upsample->methods[ci] = h2v2_fancy_upsample;

	upsample->pub.need_context_rows = TRUE;

      } else

	upsample->methods[ci] = h2v2_upsample;

    } else if ((h_out_group % h_in_group) == 0 &&

	       (v_out_group % v_in_group) == 0) {

      /* Generic integral-factors upsampling method */

      upsample->methods[ci] = int_upsample;

      upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);

      upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);

    } else

      ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);

    if (need_buffer) {

      upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)

	((j_common_ptr) cinfo, JPOOL_IMAGE,

	 (JDIMENSION) jround_up((long) cinfo->output_width,

				(long) cinfo->max_h_samp_factor),

	 (JDIMENSION) cinfo->max_v_samp_factor);

    }

  }

}