File: siscale.c

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/* Copyright (C) 2001-2006 Artifex Software, Inc.
   All Rights Reserved.
  
   This software is provided AS-IS with no warranty, either express or
   implied.

   This software is distributed under license and may not be copied, modified
   or distributed except as expressly authorized under the terms of that
   license.  Refer to licensing information at http://www.artifex.com/
   or contact Artifex Software, Inc.,  7 Mt. Lassen Drive - Suite A-134,
   San Rafael, CA  94903, U.S.A., +1(415)492-9861, for further information.
*/

/* $Id: siscale.c 9872 2009-07-20 05:10:46Z alexcher $ */
/* Image scaling filters */
#include "math_.h"
#include "memory_.h"
#include "stdio_.h"
#include "stdint_.h"
#include "gdebug.h"
#include "strimpl.h"
#include "siscale.h"

/*
 *    Image scaling code is based on public domain code from
 *      Graphics Gems III (pp. 414-424), Academic Press, 1992.
 */

/* ---------------- ImageScaleEncode/Decode ---------------- */

/* Auxiliary structures. */
typedef struct {
    float weight;		/* float or scaled fraction */
} CONTRIB;

typedef struct {
    int index;			/* index of first element in list of */
    /* contributors */
    int n;			/* number of contributors */
    /* (not multiplied by stride) */
    int first_pixel;		/* offset of first value in source data */
} CLIST;

/* ImageScaleEncode / ImageScaleDecode */
typedef struct stream_IScale_state_s {
    /* The client sets the params values before initialization. */
    stream_image_scale_state_common;  /* = state_common + params */
    /* The init procedure sets the following. */
    int sizeofPixelIn;		/* bytes per input value, 1 or 2 */
    int sizeofPixelOut;		/* bytes per output value, 1 or 2 */
    void /*PixelIn */ *src;
    void /*PixelOut */ *dst;
    byte *tmp;
    CLIST *contrib;
    CONTRIB *items;
    /* The following are updated dynamically. */
    int src_y;
    uint src_offset, src_size;
    int dst_y;
    int src_y_offset;
    uint dst_offset, dst_size;
    CLIST dst_next_list;	/* for next output value */
    int dst_last_index;		/* highest index used in list */
    CONTRIB dst_items[MAX_ISCALE_SUPPORT];	/* ditto */
} stream_IScale_state;

gs_private_st_ptrs5(st_IScale_state, stream_IScale_state,
    "ImageScaleEncode/Decode state",
    iscale_state_enum_ptrs, iscale_state_reloc_ptrs,
    dst, src, tmp, contrib, items);

/* ------ Digital filter definition ------ */

/* Mitchell filter definition */
#define Mitchell_support 2.0
#define B (1.0 / 3.0)
#define C (1.0 / 3.0)
static double
Mitchell_filter(double t)
{
    double t2 = t * t;

    if (t < 0)
	t = -t;

    if (t < 1)
	return
	    ((12 - 9 * B - 6 * C) * (t * t2) +
	     (-18 + 12 * B + 6 * C) * t2 +
	     (6 - 2 * B)) / 6;
    else if (t < 2)
	return
	    ((-1 * B - 6 * C) * (t * t2) +
	     (6 * B + 30 * C) * t2 +
	     (-12 * B - 48 * C) * t +
	     (8 * B + 24 * C)) / 6;
    else
	return 0;
}

#define filter_support Mitchell_support
#define filter_proc Mitchell_filter
#define fproc(t) filter_proc(t)
#define fWidthIn filter_support

/*
 * The environment provides the following definitions:
 *      double fproc(double t)
 *      double fWidthIn
 *      PixelTmp {min,max,unit}PixelTmp
 */
#define CLAMP(v, mn, mx)\
  (v < mn ? mn : v > mx ? mx : v)

/* ------ Auxiliary procedures ------ */

/* Define the minimum scale. */
#define min_scale ((fWidthIn * 2) / (MAX_ISCALE_SUPPORT - 1.01))

/* Calculate the support for a given scale. */
/* The value is always in the range 1 .. MAX_ISCALE_SUPPORT. */
static int
contrib_pixels(double scale)
{
    return (int)(fWidthIn / (scale >= 1.0 ? 1.0 : max(scale, min_scale))
		 * 2 + 1.5);
}

/* Pre-calculate filter contributions for a row or a column. */
/* Return the highest input pixel index used. */
static int
calculate_contrib(
	/* Return weight list parameters in contrib[0 .. size-1]. */
		     CLIST * contrib,
	/* Store weights in items[0 .. contrib_pixels(scale)*size-1]. */
	/* (Less space than this may actually be needed.) */
		     CONTRIB * items,
	/* The output image is scaled by 'scale' relative to the input. */
		     double scale,
	/* Start generating weights for input pixel 'starting_output_index'. */
		     int starting_output_index,
	/* Offset of input subimage from the input image start. */
		     int src_y_offset,
	/* Entire output image size. */
		     int dst_size,
	/* Entire input image size. */
		     int src_size,
	/* Generate 'size' weight lists. */
		     int size,
	/* Limit pixel indices to 'limit', for clamping at the edges */
	/* of the image. */
		     int limit,
	/* Wrap pixel indices modulo 'modulus'. */
		     int modulus,
	/* Successive pixel values are 'stride' distance apart -- */
	/* normally, the number of color components. */
		     int stride,
	/* The unit of output is 'rescale_factor' times the unit of input. */
		     double rescale_factor
)
{
    double WidthIn, fscale;
    bool squeeze;
    int npixels;
    int i, j;
    int last_index = -1;

    if_debug1('w', "[w]calculate_contrib scale=%lg\n", scale);
    if (scale < 1.0) {
	double clamped_scale = max(scale, min_scale);

	WidthIn = fWidthIn / clamped_scale;
	fscale = 1.0 / clamped_scale;
	squeeze = true;
    } else {
	WidthIn = fWidthIn;
	fscale = 1.0;
	squeeze = false;
    }
    npixels = (int)(WidthIn * 2 + 1);

    for (i = 0; i < size; ++i) {
	/* Here we need :
	   double scale = (double)dst_size / src_size;
	   float dst_offset_fraction = floor(dst_offset) - dst_offset;
	   double center = (starting_output_index  + i + dst_offset_fraction + 0.5) / scale - 0.5;
	   int left = (int)ceil(center - WidthIn);
	   int right = (int)floor(center + WidthIn);
	   We can't compute 'right' in floats because float arithmetics is not associative.
	   In older versions tt caused a 1 pixel bias of image bands due to 
	   rounding direction appears to depend on src_y_offset. So compute in rationals.
	   Since pixel center fall to half integers, we subtract 0.5 
	   in the image space and add 0.5 in the device space.
	 */
	int dst_y_offset_fraction_num = (int)((int64_t)src_y_offset * dst_size % src_size) * 2 <= src_size
			? -(int)((int64_t)src_y_offset * dst_size % src_size)
			: src_size - (int)((int64_t)src_y_offset * dst_size % src_size);
	int center_denom = dst_size * 2; 
	int64_t center_num = /* center * center_denom * 2 = */ 
	    (starting_output_index  + i) * src_size * 2 + src_size + dst_y_offset_fraction_num * 2 - dst_size;
	int left = (int)ceil((center_num - WidthIn * center_denom) / center_denom);
	int right = (int)floor((center_num + WidthIn * center_denom) / center_denom);
	double center = (double)center_num / center_denom;
#define clamp_pixel(j) (j < 0 ? 0 : j >= limit ? limit - 1 : j)
	int first_pixel = clamp_pixel(left);
	int last_pixel = clamp_pixel(right);
	CONTRIB *p;

	if_debug4('w', "[w]i=%d, i+offset=%lg scale=%lg center=%lg : ", starting_output_index + i, 
		starting_output_index + i + (double)src_y_offset / src_size * dst_size, scale, center);
	if (last_pixel > last_index)
	    last_index = last_pixel;
	contrib[i].first_pixel = (first_pixel % modulus) * stride;
	contrib[i].n = last_pixel - first_pixel + 1;
	contrib[i].index = i * npixels;
	p = items + contrib[i].index;
	for (j = 0; j < npixels; ++j)
	    p[j].weight = 0;
	if (squeeze) {
            double sum = 0;
	    for (j = left; j <= right; ++j)
		sum += fproc((center - j) / fscale) / fscale;
	    for (j = left; j <= right; ++j) {
		double weight = fproc((center - j) / fscale) / fscale / sum;
		int n = clamp_pixel(j);
		int k = n - first_pixel;

                p[k].weight +=
		    (float) (weight * rescale_factor);
		if_debug2('w', " %d %f", k, (float)p[k].weight);
	    }

	} else {
            double sum = 0;
	    for (j = left; j <= right; ++j)
		sum += fproc(center - j);
	    for (j = left; j <= right; ++j) {
		double weight = fproc(center - j) / sum;
		int n = clamp_pixel(j);
		int k = n - first_pixel;

		p[k].weight +=
		    (float) (weight * rescale_factor);
		if_debug2('w', " %d %f", k, (float)p[k].weight);
	    }
	}
	if_debug0('w', "\n");
    }
    return last_index;
}


/* Apply filter to zoom horizontally from src to tmp. */
static void
zoom_x(byte * tmp, const void /*PixelIn */ *src, int sizeofPixelIn,
       int tmp_width, int WidthIn, int Colors, const CLIST * contrib,
       const CONTRIB * items)
{
    int c, i;

    for (c = 0; c < Colors; ++c) {
	byte *tp = tmp + c;
	const CLIST *clp = contrib;

	if_debug1('W', "[W]zoom_x color %d:", c);
	if (sizeofPixelIn == 1) {
	    const byte *raster = (const byte *)src + c;

	    for ( i = 0; i < tmp_width; tp += Colors, ++clp, ++i ) {
	       	double weight = 0;
		int pixel, j = clp->n;
		const byte *pp = raster + clp->first_pixel;
		const CONTRIB *cp = items + clp->index;

		switch ( Colors ) {
		  case 1:
		      for ( ; j > 0; pp += 1, ++cp, --j )
		          weight += *pp * cp->weight;
		      break;
		  case 3:
		      for ( ; j > 0; pp += 3, ++cp, --j )
		          weight += *pp * cp->weight;
		      break;
		  default:
		      for ( ; j > 0; pp += Colors, ++cp, --j )
		          weight += *pp * cp->weight;
		}
		pixel = (int)(weight + 0.5);
		if_debug1('W', " %x", pixel);
		*tp = (byte)CLAMP(pixel, 0, 255);
	    }
	} else {		/* sizeofPixelIn == 2 */
	    const bits16 *raster = (const bits16 *)src + c;
	    for ( i = 0; i < tmp_width; tp += Colors, ++clp, ++i ) {
            	double weight = 0;
		int pixel, j = clp->n;
		const bits16 *pp = raster + clp->first_pixel;
		const CONTRIB *cp = items + clp->index;

		switch ( Colors ) {
		  case 1:
		      for ( ; j > 0; pp += 1, ++cp, --j )
		          weight += *pp * cp->weight;
		      break;
		  case 3:
		      for ( ; j > 0; pp += 3, ++cp, --j )
		          weight += *pp * cp->weight;
		      break;
		  default:
		      for ( ; j > 0; pp += Colors, ++cp, --j )
		          weight += *pp * cp->weight;
		}
		pixel = (int)(weight + 0.5);
		if_debug1('W', " %x", pixel);
		*tp = (byte)CLAMP(pixel, 0, 255);
	    }
	}
	if_debug0('W', "\n");
    }
}


/*
 * Apply filter to zoom vertically from tmp to dst.
 * This is simpler because we can treat all columns identically
 * without regard to the number of samples per pixel.
 */
static void
zoom_y(void /*PixelOut */ *dst, int sizeofPixelOut, uint MaxValueOut,
       const byte * tmp, int WidthOut, int tmp_width,
       int Colors, const CLIST * contrib, const CONTRIB * items)
{
    int kn = WidthOut * Colors;
    int cn = contrib->n;
    int first_pixel = contrib->first_pixel;
    const CONTRIB *cbp = items + contrib->index;
    int kc;
    int max_weight = MaxValueOut;

    if_debug0('W', "[W]zoom_y: ");

    if (sizeofPixelOut == 1) {
	for ( kc = 0; kc < kn; ++kc ) {
	    double weight = 0;
	    const byte *pp = &tmp[kc + first_pixel];
	    int pixel, j = cn;
	    const CONTRIB *cp = cbp;

	    for ( ; j > 0; pp += kn, ++cp, --j )
		weight += *pp * cp->weight;
	    pixel = (int)(weight + 0.5);
	    if_debug1('W', " %x", pixel);
	    ((byte *)dst)[kc] = (byte)CLAMP(pixel, 0, max_weight);
	}
    } else {			/* sizeofPixelOut == 2 */
	for ( kc = 0; kc < kn; ++kc ) {
	    double weight = 0;
	    const byte *pp = &tmp[kc + first_pixel];
	    int pixel, j = cn;
	    const CONTRIB *cp = cbp;

	    for ( ; j > 0; pp += kn, ++cp, --j )
		weight += *pp * cp->weight;
	    pixel = (int)(weight + 0.5);
	    if_debug1('W', " %x", pixel);
	    ((bits16 *)dst)[kc] = (bits16)CLAMP(pixel, 0, max_weight);
	}
    }
    if_debug0('W', "\n");
}

/* ------ Stream implementation ------ */

/* Forward references */
static void s_IScale_release(stream_state * st);

/* Calculate the weights for an output row. */
static void
calculate_dst_contrib(stream_IScale_state * ss, int y)
{
    uint row_size = ss->params.WidthOut * ss->params.Colors;
    int last_index =
    calculate_contrib(&ss->dst_next_list, ss->dst_items, 
		      (double)ss->params.EntireHeightOut / ss->params.EntireHeightIn,
		      y, ss->src_y_offset, ss->params.EntireHeightOut, ss->params.EntireHeightIn, 
		      1, ss->params.HeightIn, MAX_ISCALE_SUPPORT, row_size,
		      (double)ss->params.MaxValueOut / 255 );
    int first_index_mod = ss->dst_next_list.first_pixel / row_size;

    if_debug2('w', "[W]calculate_dst_contrib for y = %d, y+offset=%d\n", y, y + ss->src_y_offset);
    ss->dst_last_index = last_index;
    last_index %= MAX_ISCALE_SUPPORT;
    if (last_index < first_index_mod) {		/* Shuffle the indices to account for wraparound. */
	CONTRIB shuffle[MAX_ISCALE_SUPPORT];
	int i;

	for (i = 0; i < MAX_ISCALE_SUPPORT; ++i) {
	    shuffle[i].weight =
		(i <= last_index ?
		 ss->dst_items[i + MAX_ISCALE_SUPPORT - first_index_mod].weight :
		 i >= first_index_mod ?
		 ss->dst_items[i - first_index_mod].weight :
		 0);
	    if_debug1('W', " %f", shuffle[i].weight);
	}
	memcpy(ss->dst_items, shuffle, MAX_ISCALE_SUPPORT * sizeof(CONTRIB));
	ss->dst_next_list.n = MAX_ISCALE_SUPPORT;
	ss->dst_next_list.first_pixel = 0;
    }
    if_debug0('W', "\n");
}

/* Set default parameter values (actually, just clear pointers). */
static void
s_IScale_set_defaults(stream_state * st)
{
    stream_IScale_state *const ss = (stream_IScale_state *) st;

    ss->src = 0;
    ss->dst = 0;
    ss->tmp = 0;
    ss->contrib = 0;
    ss->items = 0;
}

/* Initialize the filter. */
static int
s_IScale_init(stream_state * st)
{
    stream_IScale_state *const ss = (stream_IScale_state *) st;
    gs_memory_t *mem = ss->memory;

    ss->sizeofPixelIn = ss->params.BitsPerComponentIn / 8;
    ss->sizeofPixelOut = ss->params.BitsPerComponentOut / 8;

    ss->src_y = 0;
    ss->src_size = ss->params.WidthIn * ss->sizeofPixelIn * ss->params.Colors;
    ss->src_offset = 0;
    ss->dst_y = 0;
    ss->src_y_offset = ss->params.src_y_offset;
    ss->dst_size = ss->params.WidthOut * ss->sizeofPixelOut * ss->params.Colors;
    ss->dst_offset = 0;

    /* create intermediate image to hold horizontal zoom */
    ss->tmp = (byte *) gs_alloc_byte_array(mem,
					   min(ss->params.HeightIn, MAX_ISCALE_SUPPORT),
			      ss->params.WidthOut * ss->params.Colors * sizeof(byte),
					       "image_scale tmp");
    ss->contrib = (CLIST *) gs_alloc_byte_array(mem,
					   max(ss->params.WidthOut, ss->params.HeightOut),
				      sizeof(CLIST), "image_scale contrib");
    ss->items = (CONTRIB *) gs_alloc_byte_array(mem,
				  contrib_pixels((double)ss->params.EntireWidthOut / 
					ss->params.EntireWidthIn) * ss->params.WidthOut,
				 sizeof(CONTRIB), "image_scale contrib[*]");
    /* Allocate buffers for 1 row of source and destination. */
    ss->dst = gs_alloc_byte_array(mem, ss->params.WidthOut * ss->params.Colors,
				  ss->sizeofPixelOut, "image_scale dst");
    ss->src = gs_alloc_byte_array(mem, ss->params.WidthIn * ss->params.Colors,
				  ss->sizeofPixelIn, "image_scale src");
    if (ss->tmp == 0 || ss->contrib == 0 || ss->items == 0 ||
	ss->dst == 0 || ss->src == 0
	) {
	s_IScale_release(st);
	return ERRC;
/****** WRONG ******/
    }
    /* Pre-calculate filter contributions for a row. */
    calculate_contrib(ss->contrib, ss->items,
		      (double)ss->params.EntireWidthOut / ss->params.EntireWidthIn,
		      0, 0, ss->params.WidthOut, ss->params.WidthIn, 
		      ss->params.WidthOut, ss->params.WidthIn, ss->params.WidthIn,
		      ss->params.Colors, 255. / ss->params.MaxValueIn);

    /* Prepare the weights for the first output row. */
    calculate_dst_contrib(ss, 0);

    return 0;

}

/* Process a buffer.  Note that this handles Encode and Decode identically. */
static int
s_IScale_process(stream_state * st, stream_cursor_read * pr,
		 stream_cursor_write * pw, bool last)
{
    stream_IScale_state *const ss = (stream_IScale_state *) st;

    /* Check whether we need to deliver any output. */

  top:while (ss->src_y > ss->dst_last_index) {	/* We have enough horizontally scaled temporary rows */
	/* to generate a vertically scaled output row. */
	uint wleft = pw->limit - pw->ptr;

	if (ss->dst_y == ss->params.HeightOut)
	    return EOFC;
	if (wleft == 0)
	    return 1;
	if (ss->dst_offset == 0) {
	    byte *row;

	    if (wleft >= ss->dst_size) {	/* We can scale the row directly into the output. */
		row = pw->ptr + 1;
		pw->ptr += ss->dst_size;
	    } else {		/* We'll have to buffer the row. */
		row = ss->dst;
	    }
	    /* Apply filter to zoom vertically from tmp to dst. */
	    zoom_y(row, ss->sizeofPixelOut, ss->params.MaxValueOut, ss->tmp,
		   ss->params.WidthOut, ss->params.WidthOut, ss->params.Colors,
		   &ss->dst_next_list, ss->dst_items);
	    /* Idiotic C coercion rules allow T* and void* to be */
	    /* inter-assigned freely, but not compared! */
	    if ((void *)row != ss->dst)		/* no buffering */
		goto adv;
	} 
	{			/* We're delivering a buffered output row. */
	    uint wcount = ss->dst_size - ss->dst_offset;
	    uint ncopy = min(wleft, wcount);

	    memcpy(pw->ptr + 1, (byte *) ss->dst + ss->dst_offset, ncopy);
	    pw->ptr += ncopy;
	    ss->dst_offset += ncopy;
	    if (ncopy != wcount)
		return 1;
	    ss->dst_offset = 0;
	}
	/* Advance to the next output row. */
      adv:++ss->dst_y;
	if (ss->dst_y != ss->params.HeightOut)
	    calculate_dst_contrib(ss, ss->dst_y);
    }

    /* Read input data and scale horizontally into tmp. */

    {
	uint rleft = pr->limit - pr->ptr;
	uint rcount = ss->src_size - ss->src_offset;

	if (rleft == 0)
	    return 0;		/* need more input */
	if (ss->src_y >= ss->params.HeightIn)
	    return ERRC;
	if (rleft >= rcount) {	/* We're going to fill up a row. */
	    const byte *row;

	    if (ss->src_offset == 0) {	/* We have a complete row.  Read the data */
		/* directly from the input. */
		row = pr->ptr + 1;
	    } else {		/* We're buffering a row in src. */
		row = ss->src;
		memcpy((byte *) ss->src + ss->src_offset, pr->ptr + 1,
		       rcount);
		ss->src_offset = 0;
	    }
	    /* Apply filter to zoom horizontally from src to tmp. */
	    if_debug2('w', "[w]zoom_x y = %d to tmp row %d\n",
		      ss->src_y, (ss->src_y % MAX_ISCALE_SUPPORT));
	    zoom_x(ss->tmp + (ss->src_y % MAX_ISCALE_SUPPORT) *
		   ss->params.WidthOut * ss->params.Colors, row,
		   ss->sizeofPixelIn, ss->params.WidthOut, ss->params.WidthIn,
		   ss->params.Colors, ss->contrib, ss->items);
	    pr->ptr += rcount;
	    ++(ss->src_y);
	    goto top;
	} else {		/* We don't have a complete row.  Copy data to src buffer. */
	    memcpy((byte *) ss->src + ss->src_offset, pr->ptr + 1, rleft);
	    ss->src_offset += rleft;
	    pr->ptr += rleft;
	    return 0;
	}
    }
}

/* Release the filter's storage. */
static void
s_IScale_release(stream_state * st)
{
    stream_IScale_state *const ss = (stream_IScale_state *) st;
    gs_memory_t *mem = ss->memory;

    gs_free_object(mem, (void *)ss->src, "image_scale src");	/* no longer const */
    ss->src = 0;
    gs_free_object(mem, ss->dst, "image_scale dst");
    ss->dst = 0;
    gs_free_object(mem, ss->items, "image_scale contrib[*]");
    ss->items = 0;
    gs_free_object(mem, ss->contrib, "image_scale contrib");
    ss->contrib = 0;
    gs_free_object(mem, ss->tmp, "image_scale tmp");
    ss->tmp = 0;
}

/* Stream template */
const stream_template s_IScale_template = {
    &st_IScale_state, s_IScale_init, s_IScale_process, 1, 1,
    s_IScale_release, s_IScale_set_defaults
};