/*
* Copyright 2014 Google Inc.
*
* Licensed 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.hefuyi.listener.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.util.LruCache;
import android.view.Gravity;
public class ScrimUtil {
private static final LruCache<Integer, Drawable> cubicGradientScrimCache = new LruCache<>(10);
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(int baseColor, int numStops, final int gravity) {
// Generate a cache key by hashing together the inputs, based on the method described in the Effective Java book
int cacheKeyHash = baseColor;
cacheKeyHash = 31 * cacheKeyHash + numStops;
cacheKeyHash = 31 * cacheKeyHash + gravity;
Drawable cachedGradient = cubicGradientScrimCache.get(cacheKeyHash);
if (cachedGradient != null) {
return cachedGradient;
}
numStops = Math.max(numStops, 2);
PaintDrawable paintDrawable = new PaintDrawable();
paintDrawable.setShape(new RectShape());
final int[] stopColors = new int[numStops];
int red = Color.red(baseColor);
int green = Color.green(baseColor);
int blue = Color.blue(baseColor);
int alpha = Color.alpha(baseColor);
for (int i = 0; i < numStops; i++) {
float x = i * 1f / (numStops - 1);
float opacity = MathUtil.constrain(0, 1, (float) Math.pow(x, 3));
stopColors[i] = Color.argb((int) (alpha * opacity), red, green, blue);
}
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;
case Gravity.CENTER_HORIZONTAL:
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;
case Gravity.CENTER_VERTICAL:
default: y0 = 0; y1 = 0; break;
}
paintDrawable.setShaderFactory(new ShapeDrawable.ShaderFactory() {
@Override
public Shader resize(int width, int height) {
return new LinearGradient(
width * x0,
height * y0,
gravity == Gravity.CENTER_VERTICAL ? width : width * x1,
gravity == Gravity.CENTER_HORIZONTAL ? height : height * y1,
gravity == Gravity.CENTER_HORIZONTAL || gravity == Gravity.CENTER_VERTICAL ? makeDoubleStopColors(stopColors) : stopColors,
null,
Shader.TileMode.CLAMP);
}
});
cubicGradientScrimCache.put(cacheKeyHash, paintDrawable);
return paintDrawable;
}
public static int[] makeDoubleStopColors(int[] stopColors) {
int length = stopColors.length;
int[] doubleStopColors = new int[length * 2];
for (int i=0;i<length;i++) {
doubleStopColors[i] = stopColors[length - 1 - i];
}
for (int j=length;j<length*2;j++) {
doubleStopColors[j] = stopColors[j - length];
}
return doubleStopColors;
}
public static class MathUtil {
public static float constrain(float min, float max, float v) {
return Math.max(min, Math.min(max, v));
}
}
}