FadingShadow.java 文件源码

/**
 * @param shadowColor The color of the shadow, e.g. 0x11000000.
 */
public FadingShadow(int shadowColor) {
    final int n = SMOOTH_ALGORITHM_INTERPOLATION_POINTS_NUM;
    float[] positions = new float[n];
    int[] colors = new int[n];
    int transparentShadowColor = shadowColor & 0x00FFFFFF;
    int shadowAlpha = Color.alpha(shadowColor);

    // Piece-wise linear interpolation of the smooth cubic function below.
    for (int i = 0; i < n; ++i) {
        float x = (float) i / (n - 1);
        // Polynomial computation by Estrin's scheme.
        float value = (1.0f - 2.2f * x) + (1.8f - 0.6f * x) * (x * x);

        positions[i] = x;
        colors[i] = (Math.round(shadowAlpha * value) << 24) | transparentShadowColor;
    }

    mShadowShader = new LinearGradient(0, 0, 0, 1, colors, positions, Shader.TileMode.CLAMP);

}