io.plaidapp.core.util.ScrimUtil.java Source code

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Here is the source code for io.plaidapp.core.util.ScrimUtil.java

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/*
 * Copyright 2018 Google LLC
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor
 * license agreements. See the NOTICE file distributed with this work for
 * additional information regarding copyright ownership. The ASF licenses this
 * file to you under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package io.plaidapp.core.util;

import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Shader;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.PaintDrawable;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.RectShape;
import android.support.annotation.ColorInt;
import android.support.v4.math.MathUtils;
import android.view.Gravity;

import io.plaidapp.core.util.ColorUtils;

/**
 * * Borrowed from github.com/romannurik/muzei
 */
public class ScrimUtil {

    private ScrimUtil() {
    }

    /**
     * Creates an approximated cubic gradient using a multi-stop linear gradient. See
     * <a href="https://plus.google.com/+RomanNurik/posts/2QvHVFWrHZf">this post</a> for more
     * details.
     */
    public static Drawable makeCubicGradientScrimDrawable(@ColorInt int baseColor, int numStops, int gravity) {
        numStops = Math.max(numStops, 2);

        PaintDrawable paintDrawable = new PaintDrawable();
        paintDrawable.setShape(new RectShape());

        final int[] stopColors = new int[numStops];

        int alpha = Color.alpha(baseColor);

        for (int i = 0; i < numStops; i++) {
            float x = i * 1f / (numStops - 1);
            float opacity = MathUtils.clamp((float) Math.pow(x, 3), 0, 1);
            stopColors[i] = ColorUtils.modifyAlpha(baseColor, (int) (alpha * opacity));
        }

        final float x0, x1, y0, y1;
        switch (gravity & Gravity.HORIZONTAL_GRAVITY_MASK) {
        case Gravity.LEFT:
            x0 = 1;
            x1 = 0;
            break;
        case Gravity.RIGHT:
            x0 = 0;
            x1 = 1;
            break;
        default:
            x0 = 0;
            x1 = 0;
            break;
        }
        switch (gravity & Gravity.VERTICAL_GRAVITY_MASK) {
        case Gravity.TOP:
            y0 = 1;
            y1 = 0;
            break;
        case Gravity.BOTTOM:
            y0 = 0;
            y1 = 1;
            break;
        default:
            y0 = 0;
            y1 = 0;
            break;
        }

        paintDrawable.setShaderFactory(new ShapeDrawable.ShaderFactory() {
            @Override
            public Shader resize(int width, int height) {
                LinearGradient linearGradient = new LinearGradient(width * x0, height * y0, width * x1, height * y1,
                        stopColors, null, Shader.TileMode.CLAMP);
                return linearGradient;
            }
        });

        return paintDrawable;
    }
}