libvips/libsrc/colour/im_LabS2LabQ.c

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2007-08-29 18:23:50 +02:00
/* @(#) im_LabS2LabQ() - convert short LAB format to IM_CODING_LABQ.
* @(#)
* @(#) int im_LabS2LabQ( IMAGE *in, IMAGE *out )
* @(#)
* @(#)
*
* 17/11/93 JC
* - adapted from im_LabQ2LabS()
* 16/11/94 JC
* - adapted to new im_wrap_oneonebuf() function
* 15/6/95 JC
* - oops! rounding was broken
* 6/6/95 JC
* - added round-to-nearest
* - somewhat slower ...
* 21/12/99 JC
* - a/b ==0 rounding was broken
*/
/*
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 <vips/vips.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
/* Convert n pels from signed short to IM_CODING_LABQ.
*/
void
imb_LabS2LabQ( signed short *in, unsigned char *out, int n )
{
int c;
signed short *p = in;
int l, a, b;
unsigned char *q = out;
unsigned char ext;
for( c = 0; c < n; c++ ) {
/* Get LAB, rounding to 10, 11, 11.
*/
l = p[0] + 16;
if( l < 0 )
l = 0;
else if( l > 32767 )
l = 32767;
l >>= 5;
/* Make sure we round -ves in the right direction!
*/
a = p[1];
if( a >= 0 )
a += 16;
else
a -= 16;
if( a < -32768 )
a = -32768;
else if( a > 32767 )
a = 32767;
a >>= 5;
b = p[2];
if( b >= 0 )
b += 16;
else
b -= 16;
if( b < -32768 )
b = -32768;
else if( b > 32767 )
b = 32767;
b >>= 5;
p += 3;
/* Extract top 8 bits.
*/
q[0] = l >> 2;
q[1] = a >> 3;
q[2] = b >> 3;
/* Form extension byte.
*/
ext = (l << 6) & 0xc0;
ext |= (a << 3) & 0x38;
ext |= b & 0x7;
q[3] = ext;
q += 4;
}
}
int
im_LabS2LabQ( IMAGE *in, IMAGE *out )
{
/* Check type.
*/
if( in->Coding != IM_CODING_NONE ) {
im_errormsg( "im_LabS2LabQ: not an uncoded image" );
return( -1 );
}
if( in->BandFmt != IM_BANDFMT_SHORT || in->Bands != 3 ) {
im_errormsg( "im_LabS2LabQ: not a 3-band signed short image" );
return( -1 );
}
/* Set up output image
*/
if( im_cp_desc( out, in ) )
return( -1 );
out->Bands = 4;
out->Type = IM_TYPE_LAB;
out->BandFmt = IM_BANDFMT_UCHAR;
out->Bbits = 8;
out->Coding = IM_CODING_LABQ;
if( im_wrapone( in, out,
(im_wrapone_fn) imb_LabS2LabQ, NULL, NULL ) )
return( -1 );
return( 0 );
}