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%%	options

copyright owner	=	Dirk Krause
copyright year	=	2017-xxxx
SPDX-License-Identifier:	BSD-3-Clause


%%	header

/**	@file	dk4pxres.h	Pixel resampling.
*/

#ifndef	DK4CONF_H_INCLUDED
#if DK4_BUILDING_DKTOOLS4
#include "dk4conf.h"
#else
#include <dktools-4/dk4conf.h>
#endif
#endif

#ifndef	DK4PXBIT_H_INCLUDED
#if DK4_BUILDING_DKTOOLS4
#include "dk4pxbit.h"
#else
#include <dktools-4/dk4pxbit.h>
#endif
#endif

/**	Structure to resample pixels.
*/
typedef struct {
	unsigned long	nom;		/**< Nominator in scale factor. */
	unsigned long	denom;		/**< Denominator in scale factor. */
	unsigned long	denom2;		/**< Half of the denominator. */
} dk4_px_resample_t;

#ifdef	__cplusplus
extern "C" {
#endif

/**	Initialize resampler structure.
	@param	pxrptr	Resampler structure to initialize.
*/

void
dk4pxres_init(dk4_px_resample_t *pxrptr);


/**	Set up resample structure for conversions.
	@param	pxrptr	Resample structure to set up.
	@param	ibits	Number of input bits.
	@param	obits	Number of output (result) bits.
	@return	1 on success, 0 on error.
*/

int
dk4pxres_setup(
	dk4_px_resample_t	*pxrptr,
	size_t				 ibits,
	size_t				 obits
);


/**	Set up resample structure for conversions for unusual maxval values.
	Input is from a range with unusual maxval, output is prepared
	for a given bit depth.
	@param	pxrptr	Resample structure to set up.
	@param	imaxval	Maximum value for input pixel data.
	@param	obits	Number of output (result) bits.
	@return	1 on success, 0 on error.
*/

int
dk4pxres_setup_from_maxval(
	dk4_px_resample_t	*pxrptr,
	dk4_px_t			 imaxval,
	size_t				 obits
);


/**	Set up resample structure for conversions for unusual maxval values.
	Input has a given bit depth, output must be in the range up to s
	specified maxval.
	@param	pxrptr	Resample structure to set up.
	@param	ibits	Input bit depth.
	@param	omaxval	Maximum value for output pixel data.
	@return	1 on success, 0 on error.
*/
int
dk4pxres_setup_to_maxval(
	dk4_px_resample_t	*pxrptr,
	size_t				 ibits,
	dk4_px_t			 omaxval
);


/**	Resample pixel component from old bit width to new bit width.
	@param	pxrptr	Resample structure to use.
	@param	in		Component value in old bit depth.
	@return	Resampling result (component value in new bit depth).
*/

dk4_px_t
dk4pxres_get(
	dk4_px_resample_t const	*pxrptr,
	dk4_px_t				 in
);


/**	Check whether a component value can be resampled without quality loss.
	@param	pxrptr	Resample structure to use.
	@param	in		Component value in old bit depth.
	@return	1 on success (no division remainder), 0 on error
	(skipped division remainder results in quality loss).
*/

int
dk4pxres_check(
	dk4_px_resample_t const	*pxrptr,
	dk4_px_t				 in
);


/**	Resample multiple values to new bit depth.
	@param	dptr	Array containing values to resample, results on output.
	@param	dsz		Number of elements in array.
	@param	pxrptr	Resample structure to use.
	@return	1 on success, 0 on error.
*/

int
dk4pxres_multiple(
	dk4_px_t				*dptr,
	size_t					 dsz,
	dk4_px_resample_t const	*pxrptr
);


#ifdef	__cplusplus
}
#endif


/* vim: set ai sw=4 ts=4 : */


%%	module

#include "dk4conf.h"

#ifndef	DK4PXRES_H_INCLUDED
#include "dk4pxres.h"
#endif

#ifndef	DK4PXBIT_H_INCLUDED
#include "dk4pxbit.h"
#endif

#if DK4_HAVE_ASSERT_H
#ifndef	ASSERT_H_INCLUDED
#include <assert.h>
#define	ASSERT_H_INCLUDED 1
#endif
#endif


$!trace-include



void
dk4pxres_init(dk4_px_resample_t *pxrptr)
{
	$? "+ dk4pxres_init ptr=%d", TR_IPTR(pxrptr)
#if	DK4_USE_ASSERT
	assert(NULL != pxrptr);
#endif
	if (NULL != pxrptr) {
		pxrptr->nom		= 255UL;
		pxrptr->denom	= 255UL;
		pxrptr->denom2	= 127UL;
	}
	$? "- dk4pxres_init"
}



int
dk4pxres_setup(
	dk4_px_resample_t	*pxrptr,
	size_t				 ibits,
	size_t				 obits
)
{
	dk4_px_t	nom;
	dk4_px_t	denom;
	int		 	back	= 0;
	$? "+ dk4pxres_setup in=%u out=%u", (unsigned)ibits, (unsigned)obits
#if	DK4_USE_ASSERT
	assert(NULL != pxrptr);
#endif
	/*
		Check pointer
	*/
	if (NULL == pxrptr) {
		goto finished;
	}
	pxrptr->nom = 255UL;
	pxrptr->denom = 255UL;
	pxrptr->denom2 = 127UL;
	/*
		Attempt to retrieve values
	*/
	nom		= dk4pxbit_get_max(obits);
	denom	= dk4pxbit_get_max(ibits);
	if ((0 == nom) || (0 == denom)) {
		goto finished;
	}
	/*
		Set values and indicate success
	*/
	pxrptr->nom		= (unsigned long)nom;
	pxrptr->denom	= (unsigned long)denom;
	pxrptr->denom2	= pxrptr->denom / 2UL;
	$? ". factor = %lu / %lu", (unsigned long)nom, (unsigned long)denom
	back = 1;
	finished:
	$? "- dk4pxres_setup %d", back
	return back;
}



int
dk4pxres_setup_from_maxval(
	dk4_px_resample_t	*pxrptr,
	dk4_px_t			 imaxval,
	size_t				 obits
)
{
	int		 		back	= 0;
	unsigned long	nom;
	unsigned long	denom;
	$? "+ dk4pxres_setup_from_maxval p=%d maxval=%u obits=%u", TR_IPTR(pxrptr), (unsigned)imaxval, (unsigned)obits
#if	DK4_USE_ASSERT
	assert(NULL != pxrptr);
#endif
	/*
		Check pointer
	*/
	if (NULL == pxrptr) {
		goto finished;
	}
	/*
		Set defaults
	*/
	pxrptr->nom = 255UL;
	pxrptr->denom = 255UL;
	pxrptr->denom2 = 127UL;
	/*
		Retrieve values
	*/
	nom = dk4pxbit_get_max(obits);
	if ((0 == nom) || (0 == imaxval)) {
		goto finished;
	}
	/*	Set values and indicate success
	*/
	pxrptr->nom		= (unsigned long)nom;
	pxrptr->denom	= denom	= (unsigned long)imaxval;
	pxrptr->denom2	= (unsigned long)imaxval / 2UL;
	$? ". factor = %lu / %lu", (unsigned long)nom, (unsigned long)denom
	back = 1;

	finished:
	$? "- dk4pxres_setup_from_maxval %d", back
	return back;
}



int
dk4pxres_setup_to_maxval(
	dk4_px_resample_t	*pxrptr,
	size_t				 ibits,
	dk4_px_t			 omaxval
)
{
	unsigned long	nom;
	unsigned long	denom;
	int			 	back	= 0;
	$? "+ dk4pxres_setup_to_maxval"
#if	DK4_USE_ASSERT
	assert(NULL != pxrptr);
#endif
	/*
		Check pointer
	*/
	if (NULL == pxrptr) { goto finished; }
	/*
		Set defaults
	*/
	pxrptr->nom = 255UL;
	pxrptr->denom = 255UL;
	pxrptr->denom2 = 127UL;
	/*
		Find nominator and denominator
	*/
	nom = (unsigned long)omaxval;
	denom = (unsigned long)dk4pxbit_get_max(ibits);
	if ((0UL == nom) || (0UL == denom)) { goto finished; }
	pxrptr->nom = nom;
	pxrptr->denom = denom;
	pxrptr->denom2 = denom / 2UL;
	$? ". factor = %lu / %lu", nom, denom
	back = 1;

	finished:
	$? "- dk4pxres_setup_to_maxval %d", back
	return back;
}



dk4_px_t
dk4pxres_get(
	dk4_px_resample_t const	*pxrptr,
	dk4_px_t				 in
)
{
	unsigned long	prod;
	dk4_px_t		back	= 0U;
	$? "+ dk4pxres_get %lu", (unsigned long)in
#if	DK4_USE_ASSERT
	assert(NULL != pxrptr);
#endif
	/*
		Check pointer
	*/
	if (NULL == pxrptr) {
		goto finished;
	}
	/*
		Leave value unchanged for equal size
	*/
	if (pxrptr->nom == pxrptr->denom) {
		back = in;
		goto finished;
	}
	/*
		Calculate
	*/
	if (0 == pxrptr->denom) {
		goto finished;
	}
	prod = (unsigned long)in * pxrptr->nom;
	back = (dk4_px_t)(prod / pxrptr->denom);
	if (pxrptr->denom2 < (prod % pxrptr->denom)) {
		back++;
	}
	finished:
	$? "- dk4pxres_get %lu", (unsigned long)back
	return back;
}



int
dk4pxres_check(
	dk4_px_resample_t const	*pxrptr,
	dk4_px_t				 in
)
{
	unsigned long	prod;
	int				back	= 0;
	$? "+ dk4pxres_check %lu", (unsigned long)in
#if	DK4_USE_ASSERT
	assert(NULL != pxrptr);
#endif
	if (NULL == pxrptr) {
		goto finished;
	}
	if (pxrptr->nom == pxrptr->denom) {
		back = 1;
		goto finished;
	}
	if (0 == pxrptr->denom) {
		goto finished;
	}
	prod = (unsigned long)in * pxrptr->nom;
	if (0 == (prod % pxrptr->denom)) {
		back = 1;
	}
	finished:
	$? "- dk4pxres_check %d", back
	return back;
}



int
dk4pxres_multiple(
	dk4_px_t				*dptr,
	size_t					 dsz,
	dk4_px_resample_t const	*pxrptr
)
{
	int		 back	= 0;
	$? "+ dk4pxres_multiple %u", (unsigned)dsz
#if	DK4_USE_ASSERT
	assert(NULL != dptr);
	assert(0 < dsz);
#endif
	if ((NULL == dptr) || (NULL == pxrptr)) {
		goto finished;
	}
	back = 1;
	while (0 < dsz--) {
		*dptr = dk4pxres_get(pxrptr, *dptr);
		dptr++;
	}
	finished:
	$? "- dk4pxres_multiple %d", back
	return back;
}



/* vim: set ai sw=4 ts=4 : */