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57 lines
1.9 KiB
57 lines
1.9 KiB
/*
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* Copyright 2021 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.ux.material.libmonet.quantize;
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import com.google.ux.material.libmonet.utils.ColorUtils;
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/**
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* Provides conversions needed for K-Means quantization. Converting input to points, and converting
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* the final state of the K-Means algorithm to colors.
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*/
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public final class PointProviderLab implements PointProvider {
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/**
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* Convert a color represented in ARGB to a 3-element array of L*a*b* coordinates of the color.
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*/
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@Override
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public double[] fromInt(int argb) {
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double[] lab = ColorUtils.labFromArgb(argb);
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return new double[] {lab[0], lab[1], lab[2]};
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}
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/** Convert a 3-element array to a color represented in ARGB. */
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@Override
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public int toInt(double[] lab) {
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return ColorUtils.argbFromLab(lab[0], lab[1], lab[2]);
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}
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/**
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* Standard CIE 1976 delta E formula also takes the square root, unneeded here. This method is
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* used by quantization algorithms to compare distance, and the relative ordering is the same,
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* with or without a square root.
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*
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* <p>This relatively minor optimization is helpful because this method is called at least once
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* for each pixel in an image.
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*/
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@Override
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public double distance(double[] one, double[] two) {
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double dL = (one[0] - two[0]);
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double dA = (one[1] - two[1]);
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double dB = (one[2] - two[2]);
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return (dL * dL + dA * dA + dB * dB);
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}
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}
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