riemersma.ts
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/**
* @preserve
* MIT License
*
* Copyright 2015-2016 Igor Bezkrovnyi
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* nearestColor.ts - part of Image Quantization Library
*/
import { IImageDitherer } from "./common"
import { HilbertCurveBase } from "./spaceFillingCurves/hilbertCurve"
import { AbstractDistanceCalculator } from "../distance/abstractDistanceCalculator"
import { PointContainer } from "../utils/pointContainer"
import { Palette } from "../utils/palette"
import { Point } from "../utils/point"
import { inRange0to255Rounded } from "../utils/arithmetic"
export class ErrorDiffusionRiemersma implements IImageDitherer {
private _distance : AbstractDistanceCalculator;
private _weights : number[];
private _errorQueueSize : number;
private _errorPropagation : number;
private _max : number;
constructor(colorDistanceCalculator : AbstractDistanceCalculator, errorQueueSize : number = 16, errorPropagation : number = 1) {
this._distance = colorDistanceCalculator;
this._errorPropagation = errorPropagation;
this._errorQueueSize = errorQueueSize;
this._max = this._errorQueueSize;
this._createWeights();
}
quantize(pointBuffer : PointContainer, palette : Palette) : PointContainer {
const curve = new HilbertCurveBase(),
pointArray = pointBuffer.getPointArray(),
width = pointBuffer.getWidth(),
height = pointBuffer.getHeight(),
errorQueue : {r : number; g : number; b : number; a : number}[] = [];
let head = 0;
for (let i = 0; i < this._errorQueueSize; i++) {
errorQueue[ i ] = { r : 0, g : 0, b : 0, a : 0 };
}
curve.walk(width, height, (x, y) => {
const p = pointArray[ x + y * width ];
let r = p.r, g = p.g, b = p.b, a = p.a;
for (let i = 0; i < this._errorQueueSize; i++) {
const weight = this._weights[ i ],
e = errorQueue[ (i + head) % this._errorQueueSize ];
r += e.r * weight;
g += e.g * weight;
b += e.b * weight;
a += e.a * weight;
}
const correctedPoint = Point.createByRGBA(
inRange0to255Rounded(r),
inRange0to255Rounded(g),
inRange0to255Rounded(b),
inRange0to255Rounded(a)
);
const quantizedPoint = palette.getNearestColor(this._distance, correctedPoint);
// update head and calculate tail
head = (head + 1) % this._errorQueueSize;
const tail = (head + this._errorQueueSize - 1) % this._errorQueueSize;
// update error with new value
errorQueue[ tail ].r = p.r - quantizedPoint.r;
errorQueue[ tail ].g = p.g - quantizedPoint.g;
errorQueue[ tail ].b = p.b - quantizedPoint.b;
errorQueue[ tail ].a = p.a - quantizedPoint.a;
// update point
p.from(quantizedPoint);
});
return pointBuffer;
}
private _createWeights() : void {
this._weights = [];
const multiplier = Math.exp(Math.log(this._max) / (this._errorQueueSize - 1));
for (let i = 0, next = 1; i < this._errorQueueSize; i++) {
this._weights[ i ] = (((next + 0.5) | 0) / this._max) * this._errorPropagation;
next *= multiplier;
}
}
}