libvips/libsrc/colour/im_Lab2LabQ.c

159 lines
3.8 KiB
C

/* @(#) im_Lab2LabQ: quantise FLOAT Lab image into 10 11 11 format
* 4 bytes per pel: l a b lsbs
* this is an image wrapper which calls line-wise packing
* Copyright K.Martinez 3/5/93
* Modified:
* 7/6/93 JC
* - adapted for partial v2
* 5/5/94 JC
* - some nint->+0.5, for speed and to ease portability
* - other nint->rint
* - now inclues <math.h>!
* 15/11/94 JC
* - all nint(), rint() removed for speed
* - now -128 rather than -127 for a, b
* - checks input type properly
* 16/11/94 JC
* - uses new im_wrap_oneonebuf()
* 22/5/95 JC
* - changed L to scale by 10.24, not 10.23
* 11/7/95 JC
* - now uses IM_RINT() for rounding
* 4/9/97 JC
* - L* = 100.0 now allowed
* 5/11/00 JC
* - go int earlier for speed up
* 20/6/02 JC
* - oops, were not clipping a/b range correctly
*/
/*
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 <vips/vips.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
/* @(#) convert float Lab to packed Lab32 format 10 11 11 bits
* works only on buffers, not IMAGEs
* Copyright 1993 K.Martinez
* Modified: 3/5/93, 16/6/93
*/
void
imb_Lab2LabQ( float *inp, unsigned char *outbuf, int n )
{
float *f, fval;
int lsbs, intv;
int Xc;
unsigned char *out;
out = outbuf;
f = inp;
for( Xc = 0; Xc < n; Xc++) {
/* Scale L up to 10 bits. Add 0.5 rather than call IM_RINT for
* speed. This will not round negatives correctly! But this
* does not matter, since L is >0. L*=100.0 -> 1023.
*/
intv = 10.23 * f[0] + 0.5; /* scale L up to 10 bits */
if( intv > 1023 )
intv = 1023;
if( intv < 0 )
intv = 0;
lsbs = (intv & 0x3) << 6; /* 00000011 -> 11000000 */
out[0] = (intv >> 2); /* drop bot 2 bits and store */
fval = 8.0 * f[1]; /* do a */
intv = IM_RINT( fval );
if( intv > 1023 )
intv = 1023;
else if( intv < -1024 )
intv = -1024;
/* Break into bits.
*/
lsbs |= (intv & 0x7) << 3; /* 00000111 -> 00111000 */
out[1] = (intv >> 3); /* drop bot 3 bits & store */
fval = 8.0 * f[2]; /* do b */
intv = IM_RINT( fval );
if( intv > 1023 )
intv = 1023;
else if( intv < -1024 )
intv = -1024;
lsbs |= (intv & 0x7);
out[2] = (intv >> 3);
out[3] = lsbs; /* store lsb band */
f += 3;
out += 4;
}
}
int
im_Lab2LabQ( IMAGE *labim, IMAGE *outim )
{
/* Check for uncoded Lab type
*/
if( labim->Coding != IM_CODING_NONE ) {
im_errormsg( "im_Lab2LabQ: uncoded input only" );
return( -1 );
}
if( labim->BandFmt != IM_BANDFMT_FLOAT || labim->Bands != 3 ) {
im_errormsg( "im_Lab2LabQ: three-band float input only" );
return( -1 );
}
/* Set up output image.
*/
if( im_cp_desc( outim, labim ) )
return( -1 );
outim->Bands = 4;
outim->Type = IM_TYPE_LAB;
outim->BandFmt = IM_BANDFMT_UCHAR;
outim->Bbits = 8;
outim->Coding = IM_CODING_LABQ;
/* Process.
*/
if( im_wrapone( labim, outim,
(im_wrapone_fn) imb_Lab2LabQ, NULL, NULL ) )
return( -1 );
return( 0 );
}