libvips/libsrc/colour/im_LabQ2disp.c

/* @(#) Turn Lab 32bit packed format into displayable rgb. Fast, but very
 * @(#) inaccurate: for display only!
 * @(#) 
 * @(#) Usage:  
 * @(#)   int im_LabQ2disp( IMAGE *in, IMAGE *out, struct im_col_display *d )
 * @(#) 
 * @(#) Returns: -1 on error, else 0
 *
 * 5/11/97 Steve Perry
 *	- adapted from old ip code
 * 7/11/97 JC
 * 	- small tidies, added to VIPS
 * 	- LUT build split into separate function
 */

/*

    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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  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 <vips/intl.h>

#include <stdio.h>
#include <math.h>
#include <assert.h>
 
#include <vips/vips.h>

#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
 
/* Hold a display characterisation, and a set of tables
 * computed from that. 
 */
typedef struct {
        struct im_col_display *disp;
        struct im_col_tab_disp *dtab;
        PEL red[ 64 * 64 * 64 ];
        PEL green[ 64 * 64 * 64 ];
        PEL blue[ 64 * 64 * 64 ];
} CalibrateInfo;

/* Do our own indexing of the arrays, to make sure we get efficient mults.
 */
#define index( L, A, B ) (L + (A << 6) + (B << 12))
 
/* Process a buffer of data.
 */
static void
imb_LabQ2disp( PEL *p, PEL *q, int n, CalibrateInfo *cal )
{ 
        int x, t;

	/* Current error.
	 */
	int le = 0;
	int ae = 0;
	int be = 0;

        for( x = 0; x < n; x++ ) {
		/* Get colour, add in error from previous pixel. 
		 */
                int L = p[0] + le;
                int A = (signed char) p[1] + ae;
                int B = (signed char) p[2] + be;
		p += 4;

		/* Look out for overflow.
		 */
		L = IM_MIN( 255, L );
		A = IM_MIN( 127, A );
		B = IM_MIN( 127, B );

		/* Find new quant error. This will always be +ve. 
		 */
		le = L & 3;
		ae = A & 3;
		be = B & 3;

		/* Scale to 0-63.
		 */
                L = (L >> 2) & 63;
                A = (A >> 2) & 63;
                B = (B >> 2) & 63;

		/* Convert to RGB.
		 */
		t = index( L, A, B );
                q[0] = cal->red[t];
                q[1] = cal->green[t];
                q[2] = cal->blue[t];
                q += 3;
        }
}

/* Build Lab->disp tables. 
 */
void *
im_LabQ2disp_build_table( IMAGE *out, struct im_col_display *d )
{
        CalibrateInfo *cal;
        int l, a, b;
	int t;

        if( !(cal = IM_NEW( out, CalibrateInfo )) )
                return( NULL );
        cal->disp = d;
        if( !(cal->dtab = im_col_make_tables_RGB( out, d ) ) ) {
		if( !out )
			im_free( cal );
                return( NULL );
	}

        /* Build our tables.
         */
        for( l = 0; l < 64; l++ ) {
                for( a = 0; a < 64; a++ ) {
                        for( b = 0; b < 64; b++ ) {
                                /* Scale to lab space.
                                 */
                                float L = (l << 2) * (100.0/256.0);
                                float A = (signed char) (a << 2);
                                float B = (signed char) (b << 2);
                                float X, Y, Z;
                                int rb, gb, bb;
                                int oflow;
 
                                /* Convert to XYZ.
                                 */
                                im_col_Lab2XYZ( L, A, B, &X, &Y, &Z );

                                /* Convert to display. 
                                 */
                                im_col_XYZ2rgb( cal->disp, cal->dtab,
                                        X, Y, Z, &rb, &gb, &bb, &oflow );

				/* Save RGB.
				 */
				t = index( l, a, b );
                                cal->red[t] = rb;
                                cal->green[t] = gb;
                                cal->blue[t] = bb;
                        }
                }
        }

	return( (void *) cal );
}
 
int 
im_LabQ2disp_table( IMAGE *in, IMAGE *out, void *table )
{
        CalibrateInfo *cal = (CalibrateInfo *) table;

        if ( in->Coding != IM_CODING_LABQ ) {
                im_errormsg( "im_LabQ2Lab: not a packed Lab image" );
                return( -1 );
        }
 
        if( im_cp_desc( out, in ) )
                return( -1 );
        out->Bands = 3;
        out->Bbits = IM_BBITS_BYTE;
        out->BandFmt = IM_BANDFMT_UCHAR;
        out->Coding = IM_CODING_NONE;
        out->Type = IM_TYPE_RGB;

        if( im_wrapone( in, out, (im_wrapone_fn) imb_LabQ2disp, cal, NULL ) )
                return( -1 );

        return( 0 );
}
 
int 
im_LabQ2disp( IMAGE *in, IMAGE *out, struct im_col_display *d )
{
        void *table;

	if( !(table = im_LabQ2disp_build_table( out, d )) ||
		im_LabQ2disp_table( in, out, table ) )
		return( -1 );

	return( 0 );
}