/*
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* Copyright (C) 2010 The Android Open Source Project
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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.nineoldandroids.animation;
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/**
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* This evaluator can be used to perform type interpolation between integer
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* values that represent ARGB colors.
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*/
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public class ArgbEvaluator implements TypeEvaluator {
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/**
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* This function returns the calculated in-between value for a color
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* given integers that represent the start and end values in the four
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* bytes of the 32-bit int. Each channel is separately linearly interpolated
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* and the resulting calculated values are recombined into the return value.
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*
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* @param fraction The fraction from the starting to the ending values
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* @param startValue A 32-bit int value representing colors in the
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* separate bytes of the parameter
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* @param endValue A 32-bit int value representing colors in the
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* separate bytes of the parameter
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* @return A value that is calculated to be the linearly interpolated
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* result, derived by separating the start and end values into separate
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* color channels and interpolating each one separately, recombining the
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* resulting values in the same way.
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*/
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public Object evaluate(float fraction, Object startValue, Object endValue) {
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int startInt = (Integer) startValue;
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int startA = (startInt >> 24);
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int startR = (startInt >> 16) & 0xff;
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int startG = (startInt >> 8) & 0xff;
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int startB = startInt & 0xff;
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int endInt = (Integer) endValue;
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int endA = (endInt >> 24);
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int endR = (endInt >> 16) & 0xff;
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int endG = (endInt >> 8) & 0xff;
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int endB = endInt & 0xff;
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return ((startA + (int)(fraction * (endA - startA))) << 24) |
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((startR + (int)(fraction * (endR - startR))) << 16) |
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((startG + (int)(fraction * (endG - startG))) << 8) |
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(startB + (int)(fraction * (endB - startB)));
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}
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}
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