113 lines
2.9 KiB
C
113 lines
2.9 KiB
C
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/*
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ucg_ccs.c
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color component slide sub library
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Universal uC Color Graphics Library
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Copyright (c) 2013, olikraus@gmail.com
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All rights reserved.
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice, this list
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of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright notice, this
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list of conditions and the following disclaimer in the documentation and/or other
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materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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e: end
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n: steps
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f(0) = s
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f(n) = e
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f(x) = m*x + s
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f(n-1) = m*(n-1) + s =!= e
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--> m = (e-s)/n
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f(x) = (e-s)/(n-1) * x + s
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f(0) = s
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f(1) = s + (e-s)/(n-1)
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*/
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#include "ucg.h"
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/*
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Setup change from "start" to "end" with a specified amount of "steps".
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After calling this procedure, ccs->current will contain the "start" value.
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*/
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void ucg_ccs_init(ucg_ccs_t *ccs, uint8_t start, uint8_t end, ucg_int_t steps)
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{
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ccs->start = start;
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ccs->num = end-start;
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ccs->den = steps-1;
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ccs->dir = 1;
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ccs->quot = ccs->num / ccs->den;
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if ( ccs->num < 0 )
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{
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ccs->num = -ccs->num;
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ccs->dir = -1;
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}
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ccs->rem = ccs->num % ccs->den;
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ccs->frac = ccs->den/2;
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ccs->current = start;
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}
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/*
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Make one step towards the "end" value.
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ccs->curront will contain the updated value.
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*/
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void ucg_ccs_step(ucg_ccs_t *ccs)
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{
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ccs->current += ccs->quot;
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ccs->frac += ccs->rem;
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if ( ccs->frac >= ccs->den )
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{
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ccs->current += ccs->dir;
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ccs->frac -= ccs->den;
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}
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}
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/*
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f(x) = (e-s)/(n-1) * x + s
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current = (num / den) * (pos / den)
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Seek to the specified "pos"ition.
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"pos" must be between 0 and "end"-1
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*/
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void ucg_ccs_seek(ucg_ccs_t *ccs, ucg_int_t pos)
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{
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ucg_int_t p;
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ccs->current = ccs->quot;
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ccs->current *= pos;
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p = ccs->rem * pos + ccs->den/2;
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if ( ccs->dir >= 0 )
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ccs->current += p / ccs->den;
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else
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ccs->current -= p / ccs->den;
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ccs->frac = p % ccs->den;
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ccs->current += ccs->start;
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}
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