152 lines
3.0 KiB
C
152 lines
3.0 KiB
C
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/* @(#) im_LabS2LabQ() - convert short LAB format to IM_CODING_LABQ.
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* @(#)
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* @(#) int im_LabS2LabQ( IMAGE *in, IMAGE *out )
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* @(#)
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* @(#)
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*
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* 17/11/93 JC
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* - adapted from im_LabQ2LabS()
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* 16/11/94 JC
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* - adapted to new im_wrap_oneonebuf() function
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* 15/6/95 JC
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* - oops! rounding was broken
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* 6/6/95 JC
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* - added round-to-nearest
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* - somewhat slower ...
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* 21/12/99 JC
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* - a/b ==0 rounding was broken
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif /*HAVE_CONFIG_H*/
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#include <vips/intl.h>
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#include <stdio.h>
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#include <vips/vips.h>
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#ifdef WITH_DMALLOC
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#include <dmalloc.h>
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#endif /*WITH_DMALLOC*/
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/* Convert n pels from signed short to IM_CODING_LABQ.
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*/
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void
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imb_LabS2LabQ( signed short *in, unsigned char *out, int n )
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{
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int c;
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signed short *p = in;
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int l, a, b;
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unsigned char *q = out;
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unsigned char ext;
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for( c = 0; c < n; c++ ) {
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/* Get LAB, rounding to 10, 11, 11.
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*/
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l = p[0] + 16;
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if( l < 0 )
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l = 0;
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else if( l > 32767 )
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l = 32767;
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l >>= 5;
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/* Make sure we round -ves in the right direction!
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*/
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a = p[1];
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if( a >= 0 )
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a += 16;
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else
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a -= 16;
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if( a < -32768 )
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a = -32768;
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else if( a > 32767 )
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a = 32767;
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a >>= 5;
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b = p[2];
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if( b >= 0 )
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b += 16;
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else
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b -= 16;
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if( b < -32768 )
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b = -32768;
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else if( b > 32767 )
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b = 32767;
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b >>= 5;
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p += 3;
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/* Extract top 8 bits.
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*/
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q[0] = l >> 2;
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q[1] = a >> 3;
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q[2] = b >> 3;
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/* Form extension byte.
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*/
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ext = (l << 6) & 0xc0;
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ext |= (a << 3) & 0x38;
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ext |= b & 0x7;
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q[3] = ext;
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q += 4;
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}
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}
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int
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im_LabS2LabQ( IMAGE *in, IMAGE *out )
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{
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/* Check type.
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*/
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if( in->Coding != IM_CODING_NONE ) {
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im_errormsg( "im_LabS2LabQ: not an uncoded image" );
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return( -1 );
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}
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if( in->BandFmt != IM_BANDFMT_SHORT || in->Bands != 3 ) {
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im_errormsg( "im_LabS2LabQ: not a 3-band signed short image" );
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return( -1 );
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}
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/* Set up output image
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*/
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if( im_cp_desc( out, in ) )
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return( -1 );
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out->Bands = 4;
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out->Type = IM_TYPE_LAB;
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out->BandFmt = IM_BANDFMT_UCHAR;
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out->Bbits = 8;
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out->Coding = IM_CODING_LABQ;
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if( im_wrapone( in, out,
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(im_wrapone_fn) imb_LabS2LabQ, NULL, NULL ) )
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return( -1 );
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return( 0 );
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}
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