mirror of https://github.com/GNOME/gimp.git
47 lines
1.9 KiB
C
47 lines
1.9 KiB
C
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/* GIMP - The GNU Image Manipulation Program
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* Copyright (C) 1995 Spencer Kimball and Peter Mattis
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU 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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*
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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 General Public License for more details.
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*
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* You should have received a copy of the GNU 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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#ifndef __PAINT_FUNCS_UTILS_H__
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#define __PAINT_FUNCS_UTILS_H__
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#define INT_MULT(a,b,t) ((t) = (a) * (b) + 0x80, ((((t) >> 8) + (t)) >> 8))
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/* This version of INT_MULT3 is very fast, but suffers from some
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slight roundoff errors. It returns the correct result 99.987
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percent of the time */
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#define INT_MULT3(a,b,c,t) ((t) = (a) * (b) * (c) + 0x7F5B, \
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((((t) >> 7) + (t)) >> 16))
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/*
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This version of INT_MULT3 always gives the correct result, but runs at
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approximatly one third the speed. */
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/* #define INT_MULT3(a,b,c,t) (((a) * (b) * (c) + 32512) / 65025.0)
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*/
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#define INT_BLEND(a,b,alpha,tmp) (INT_MULT((a) - (b), alpha, tmp) + (b))
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/* A drawable has an alphachannel if contains either 4 or 2 bytes data
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* aka GRAYA and RGBA and thus the macro below works. This will have
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* to change if we support bigger formats. We'll do it so for now because
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* masking is always cheaper than passing parameters over the stack. */
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/* FIXME: Move to a global place */
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#define HAS_ALPHA(bytes) (~bytes & 1)
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#endif /* __PAINT_FUNCS_UTILS_H__ */
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