lottie/src/main/java/com/airbnb/lottie/ScaleKeyframeAnimation.java

package com.airbnb.lottie;

import android.view.animation.Interpolator;

import java.util.List;

import static com.airbnb.lottie.MiscUtils.lerp;

class ScaleKeyframeAnimation extends KeyframeAnimation<ScaleXY> {
  private final ScaleXY outTransform = new ScaleXY();
  private final List<ScaleXY> transforms;

  ScaleKeyframeAnimation(long duration, LottieComposition composition, List<Float> keyTimes,
      List<ScaleXY> transforms, List<Interpolator> interpolators) {
    super(duration, composition, keyTimes, interpolators);
    this.transforms = transforms;
  }

  @Override public ScaleXY getValue() {
    if (progress <= 0f) {
      return transforms.get(0);
    } else if (progress >= 1f) {
      return transforms.get(transforms.size() - 1);
    }

    int keyframeIndex = getKeyframeIndex();

    float startKeytime = keyTimes.get(keyframeIndex);
    float endKeytime = keyTimes.get(keyframeIndex + 1);

    float percentageIntoFrame = 0;
    if (!isDiscrete) {
      percentageIntoFrame = (progress - startKeytime) / (endKeytime - startKeytime);
      if (interpolators != null) {
        percentageIntoFrame =
            interpolators.get(keyframeIndex).getInterpolation(percentageIntoFrame);
      }
    }

    ScaleXY startTransform = transforms.get(keyframeIndex);
    ScaleXY endTransform = transforms.get(keyframeIndex + 1);

    outTransform.scale(
        lerp(startTransform.getScaleX(), endTransform.getScaleX(), percentageIntoFrame),
        lerp(startTransform.getScaleY(), endTransform.getScaleY(), percentageIntoFrame));
    return outTransform;
  }
}