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resamplerLinear.js
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resamplerLinear.js
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/*
* Copyright (C) 2015 Stefano D'Angelo <zanga.mail@gmail.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*** Simple linear resampler object (without anti-aliasing). ***/
canvasPlot.resamplerLinear = Object.create(canvasPlot.resampler);
/* Private member. */
canvasPlot.resamplerLinear.prev = NaN;
canvasPlot.resamplerLinear.update = function () {
this.prev = NaN;
};
canvasPlot.resamplerLinear.process = function (yIn, yOut, firstIn, firstOut,
countIn, countOut, rw) {
var lastIn = firstIn + countIn - 1;
var lastOut = firstOut + countOut - 1;
var j = firstOut;
var d = yIn[firstIn] - this.prev;
for (; this.offset < 0.0 && j <= lastOut;
this.offset += this.stepRatio, j++)
yOut[j] = yIn[firstIn] + this.offset * d;
if (this.offset == 0.0 && j <= lastOut) {
yOut[j] = yIn[firstIn];
this.offset += this.stepRatio;
j++;
}
var i = firstIn + this.offset;
var il = -1; // force update on first run
var ih;
for (; i <= lastIn && j <= lastOut; i += this.stepRatio, j++) {
var ix = i - il;
if (ix > 1.0) {
ih = Math.ceil(i);
il = ih - 1;
ix = i - il;
d = yIn[ih] - yIn[il];
}
yOut[j] = yIn[il] + ix * d;
}
rw.nextOut = j;
rw.nextIn = Math.floor(i);
if (rw.nextIn <= lastIn) {
this.prev = yIn[rw.nextIn];
rw.nextIn++;
}
this.offset = i - rw.nextIn;
};