83 lines
2.5 KiB
Java
83 lines
2.5 KiB
Java
/*
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* Copyright (C) 2014 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.android.systemui;
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import android.graphics.Bitmap;
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/**
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* Utility class for image analysis and processing.
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*/
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public class ImageUtils {
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// Amount (max is 255) that two channels can differ before the color is no longer "gray".
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private static final int TOLERANCE = 20;
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// Alpha amount for which values below are considered transparent.
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private static final int ALPHA_TOLERANCE = 50;
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private int[] mTempBuffer;
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/**
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* Checks whether a bitmap is grayscale. Grayscale here means "very close to a perfect
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* gray".
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*/
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public boolean isGrayscale(Bitmap bitmap) {
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final int height = bitmap.getHeight();
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final int width = bitmap.getWidth();
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int size = height*width;
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ensureBufferSize(size);
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bitmap.getPixels(mTempBuffer, 0, width, 0, 0, width, height);
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for (int i = 0; i < size; i++) {
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if (!isGrayscale(mTempBuffer[i])) {
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return false;
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}
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}
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return true;
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}
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/**
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* Makes sure that {@code mTempBuffer} has at least length {@code size}.
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*/
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private void ensureBufferSize(int size) {
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if (mTempBuffer == null || mTempBuffer.length < size) {
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mTempBuffer = new int[size];
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}
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}
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/**
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* Classifies a color as grayscale or not. Grayscale here means "very close to a perfect
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* gray"; if all three channels are approximately equal, this will return true.
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*
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* Note that really transparent colors are always grayscale.
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*/
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public boolean isGrayscale(int color) {
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int alpha = 0xFF & (color >> 24);
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if (alpha < ALPHA_TOLERANCE) {
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return true;
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}
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int r = 0xFF & (color >> 16);
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int g = 0xFF & (color >> 8);
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int b = 0xFF & color;
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return Math.abs(r - g) < TOLERANCE
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&& Math.abs(r - b) < TOLERANCE
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&& Math.abs(g - b) < TOLERANCE;
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}
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}
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