libvips/libvips/deprecated/im_vips2mask.c

/* im_vips2mask
 *
 * Author: J.Cupitt
 * Written on: 6/6/94
 * Modified on:
 *
 * 16/10/06
 * 	- allow 1xn-band images too
 * 23/2/07
 * 	- oop, broken for nx1 m-band images 
 * 	- now casts to double for you
 * 1/2/10
 * 	- gtkdoc
 */

/*

    This file is part of VIPS.
    
    VIPS is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301  USA

 */

/*

    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <string.h>

#include <vips/vips.h>
#include <vips/vips7compat.h>

/**
 * im_vips2mask:
 * @in: input image
 * @filename: name for output mask 
 *
 * Make a mask from an image. All images are cast to %IM_BANDFMT_DOUBLE
 * before processing. There are two cases for handling bands:
 *
 * If the image has a single band, im_vips2mask() will write a mask the same
 * size as the image.
 *
 * If the image has more than one band, it must be one pixel high or wide. In
 * this case the output mask uses that axis to represent band values.
 *
 * See also: im_mask2vips(), im_measure_area().
 *
 * Returns: a #DOUBLEMASK with @outname set as the name, or NULL on error
 */
DOUBLEMASK *
im_vips2mask( IMAGE *in, const char *filename )
{
	int width, height;
	DOUBLEMASK *out;

	/* double* only: cast if necessary.
	 */
	if( in->BandFmt != IM_BANDFMT_DOUBLE ) {
		IMAGE *t;

		if( !(t = im_open( "im_vips2mask", "p" )) )
			return( NULL );
		if( im_clip2fmt( in, t, IM_BANDFMT_DOUBLE ) ||
			!(out = im_vips2mask( t, filename )) ) {
			im_close( t );
			return( NULL );
		}
		im_close( t );

		return( out );
	}

	/* Check the image.
	 */
	if( im_incheck( in ) ||
		im_check_uncoded( "im_vips2mask", in ) )
		return( NULL );

	if( in->Bands == 1 ) {
		width = in->Xsize;
		height = in->Ysize;
	}
	else if( in->Xsize == 1 ) {
		width = in->Bands;
		height = in->Ysize;
	}
	else if( in->Ysize == 1 ) {
		width = in->Xsize;
		height = in->Bands;
	}
	else {
		im_error( "im_vips2mask", 
			"%s", _( "one band, nx1, or 1xn images only" ) );
		return( NULL );
	}

	if( !(out = im_create_dmask( filename, width, height )) )
		return( NULL );
	if( in->Bands > 1 && in->Ysize == 1 ) {
		double *data = (double *) in->data;
		int x, y;

		/* Need to transpose: the image is RGBRGBRGB, we need RRRGGGBBB.
		 */
		for( y = 0; y < height; y++ )
			for( x = 0; x < width; x++ )
				out->coeff[x + y * width] =
					data[x * height + y];
	}
	else
		memcpy( out->coeff, in->data, 
			width * height * sizeof( double ) );

	out->scale = vips_image_get_scale( in );
	out->offset = vips_image_get_offset( in );

	return( out );
}

INTMASK *
im_vips2imask( IMAGE *in, const char *filename )
{
	int width, height;
	INTMASK *out;

	double *data;
	int x, y;
	double double_result;
	int int_result;

	/* double* only: cast if necessary.
	 */
	if( in->BandFmt != IM_BANDFMT_DOUBLE ) {
		IMAGE *t;

		if( !(t = im_open( "im_vips2imask", "p" )) )
			return( NULL );
		if( im_clip2fmt( in, t, IM_BANDFMT_DOUBLE ) ||
			!(out = im_vips2imask( t, filename )) ) {
			im_close( t );
			return( NULL );
		}
		im_close( t );

		return( out );
	}

	/* Check the image.
	 */
	if( im_incheck( in ) ||
		im_check_uncoded( "im_vips2imask", in ) )
		return( NULL );

	if( in->Bands == 1 ) {
		width = in->Xsize;
		height = in->Ysize;
	}
	else if( in->Xsize == 1 ) {
		width = in->Bands;
		height = in->Ysize;
	}
	else if( in->Ysize == 1 ) {
		width = in->Xsize;
		height = in->Bands;
	}
	else {
		im_error( "im_vips2imask", 
			"%s", _( "one band, nx1, or 1xn images only" ) );
		return( NULL );
	}

	data = (double *) in->data;
	if( !(out = im_create_imask( filename, width, height )) )
		return( NULL );

	/* We want to make an intmask which has the same input to output ratio
	 * as the double image.
	 *
	 * Imagine convolving with the double image, what's the ratio of
	 * brightness between input and output? We want the same ratio for the
	 * int version, if we can.
	 *
	 * Imagine an input image where every pixel is 1, what will the output
	 * be?
	 */
	double_result = 0;
	for( y = 0; y < height; y++ )
		for( x = 0; x < width; x++ )
			double_result += data[x + width * y];
	double_result /= vips_image_get_scale( in );

	for( y = 0; y < height; y++ )
		for( x = 0; x < width; x++ )
			if( in->Bands > 1 && in->Ysize == 1 ) 
				/* Need to transpose: the image is RGBRGBRGB, 
				 * we need RRRGGGBBB.
				 */
				out->coeff[x + y * width] =
					VIPS_RINT( data[x * height + y] );
			else
				out->coeff[x + y * width] =
					VIPS_RINT( data[x + y * width] );

	out->scale = VIPS_RINT( vips_image_get_scale( in ) );
	if( out->scale == 0 )
		out->scale = 1;
	out->offset = VIPS_RINT( vips_image_get_offset( in ) );

	/* Now convolve a 1 everywhere image with the int version we've made,
	 * what do we get?
	 */
	int_result = 0;
	for( y = 0; y < height; y++ )
		for( x = 0; x < width; x++ )
			int_result += out->coeff[x + width * y];
	int_result /= out->scale;

	/* And adjust the scale to get as close to a match as we can. 
	 */
	out->scale = VIPS_RINT( out->scale + (int_result - double_result) );
	if( out->scale == 0 ) 
		out->scale = 1;

	return( out );
}