tests/tests/systemui/src/android/systemui/cts/LightBarTests.java - platform/cts - Git at Google

 /*
  * Copyright (C) 2015 The Android Open Source Project
  *
  * 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 android.systemui.cts;

 import static android.support.test.InstrumentationRegistry.getInstrumentation;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;

 import android.app.ActivityManager;
 import android.app.Notification;
 import android.app.NotificationChannel;
 import android.app.NotificationManager;
 import android.app.UiAutomation;
 import android.content.Context;
 import android.content.pm.PackageManager;
 import android.graphics.Bitmap;
 import android.graphics.Color;
 import android.os.SystemClock;
 import android.support.test.rule.ActivityTestRule;
 import android.support.test.runner.AndroidJUnit4;
 import android.view.InputDevice;
 import android.view.MotionEvent;

 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;

 /**
  * Test for light status bar.
  *
  * atest CtsSystemUiTestCases:LightBarTests
  */
 @RunWith(AndroidJUnit4.class)
 public class LightBarTests extends LightBarTestBase {

     public static final String TAG = "LightStatusBarTests";

     private static final int WAIT_TIME = 2000;

     /**
      * Color may be slightly off-spec when resources are resized for lower densities. Use this error
      * margin to accommodate for that when comparing colors.
      */
     private static final int COLOR_COMPONENT_ERROR_MARGIN = 20;

     private final String NOTIFICATION_TAG = "TEST_TAG";
     private final String NOTIFICATION_CHANNEL_ID = "test_channel";
     private final String NOTIFICATION_GROUP_KEY = "test_group";
     private NotificationManager mNm;

     @Rule
     public ActivityTestRule<LightBarActivity> mActivityRule = new ActivityTestRule<>(
             LightBarActivity.class);

     @Test
     public void testLightStatusBarIcons() throws Throwable {
         assumeHasColoredStatusBar(mActivityRule);

         mNm = (NotificationManager) getInstrumentation().getContext()
                 .getSystemService(Context.NOTIFICATION_SERVICE);
         NotificationChannel channel1 = new NotificationChannel(NOTIFICATION_CHANNEL_ID,
                 NOTIFICATION_CHANNEL_ID, NotificationManager.IMPORTANCE_LOW);
         mNm.createNotificationChannel(channel1);

         // post 10 notifications to ensure enough icons in the status bar
         for (int i = 0; i < 10; i++) {
             Notification.Builder noti1 = new Notification.Builder(getInstrumentation().getContext(),
                     NOTIFICATION_CHANNEL_ID)
                     .setSmallIcon(R.drawable.ic_save)
                     .setChannelId(NOTIFICATION_CHANNEL_ID)
                     .setPriority(Notification.PRIORITY_LOW)
                     .setGroup(NOTIFICATION_GROUP_KEY);
             mNm.notify(NOTIFICATION_TAG, i, noti1.build());
         }
         Thread.sleep(WAIT_TIME);
         Bitmap beforeBitmap = takeStatusBarScreenshot(mActivityRule.getActivity());

         requestLightBars(Color.RED /* background */);
         Thread.sleep(WAIT_TIME);

         Bitmap bitmap = takeStatusBarScreenshot(mActivityRule.getActivity());
         Bitmap result = treatCutoutAsBackground(beforeBitmap, bitmap);
         if (beforeBitmap != null) {
             beforeBitmap.recycle();
         }
         if (bitmap != null && bitmap != result) {
             bitmap.recycle();
         }

         Stats s = evaluateLightBarBitmap(result, Color.RED /* background */);
         assertLightStats(result, s);

         mNm.cancelAll();
         mNm.deleteNotificationChannel(NOTIFICATION_CHANNEL_ID);
     }

     private Bitmap treatCutoutAsBackground(Bitmap before, Bitmap after) {
         if (before == null || after == null || before.getWidth() != after.getWidth()
                 || before.getHeight() != after.getHeight()) {
             return after;
         }

         Bitmap result = after.copy(Bitmap.Config.ARGB_8888, true);

         final int width = before.getWidth();
         final int height = after.getHeight();
         int[] beforePixels = new int[height * width];
         before.getPixels(beforePixels, 0, width, 0, 0, width, height);
         int[] afterPixels = new int[height * width];
         after.getPixels(afterPixels, 0, width, 0, 0, width, height);

         for (int i = 0; i < height; i++) {
             for (int j = 0; j < width; j++) {
                 int cBefore = beforePixels[i * width + j];
                 int cAfter = afterPixels[i * width + j];

                 if (cBefore == cAfter && Color.luminance(cAfter) < 0.01f) {
                     result.setPixel(j, i, Color.RED);
                 }
             }
         }

         return result;
     }

     @Test
     public void testLightNavigationBar() throws Throwable {
         assumeHasColorNavigationBar(mActivityRule);

         requestLightBars(Color.RED /* background */);
         Thread.sleep(WAIT_TIME);

         // Inject a cancelled interaction with the nav bar to ensure it is at full opacity.
         int x = mActivityRule.getActivity().getWidth() / 2;
         int y = mActivityRule.getActivity().getBottom() + 10;
         injectCanceledTap(x, y);
         Thread.sleep(WAIT_TIME);

         Bitmap bitmap = takeNavigationBarScreenshot(mActivityRule.getActivity());
         Stats s = evaluateLightBarBitmap(bitmap, Color.RED /* background */);
         assertLightStats(bitmap, s);
     }

     private void injectCanceledTap(int x, int y) {
         long downTime = SystemClock.uptimeMillis();
         injectEvent(MotionEvent.ACTION_DOWN, x, y, downTime);
         injectEvent(MotionEvent.ACTION_CANCEL, x, y, downTime);
     }

     private void injectEvent(int action, int x, int y, long downTime) {
         final UiAutomation automation = getInstrumentation().getUiAutomation();
         final long eventTime = SystemClock.uptimeMillis();
         MotionEvent event = MotionEvent.obtain(downTime, eventTime, action, x, y, 0);
         event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
         assertTrue(automation.injectInputEvent(event, true));
         event.recycle();
     }

     private void assertLightStats(Bitmap bitmap, Stats s) {
         boolean success = false;
         try {
             assertMoreThan("Not enough background pixels", 0.3f,
                     (float) s.backgroundPixels / s.totalPixels(),
                     "Is the bar background showing correctly (solid red)?");

             assertMoreThan("Not enough pixels colored as in the spec", 0.3f,
                     (float) s.iconPixels / s.foregroundPixels(),
                     "Are the bar icons colored according to the spec "
                             + "(60% black and 24% black)?");

             assertLessThan("Too many lighter pixels lighter than the background", 0.05f,
                     (float) s.sameHueLightPixels / s.foregroundPixels(),
                     "Are the bar icons dark?");

             assertLessThan("Too many pixels with a changed hue", 0.05f,
                     (float) s.unexpectedHuePixels / s.foregroundPixels(),
                     "Are the bar icons color-free?");

             success = true;
         } finally {
             if (!success) {
                 dumpBitmap(bitmap);
             }
         }
     }

     private void assertMoreThan(String what, float expected, float actual, String hint) {
         if (!(actual > expected)) {
             fail(what + ": expected more than " + expected * 100 + "%, but only got " + actual * 100
                     + "%; " + hint);
         }
     }

     private void assertLessThan(String what, float expected, float actual, String hint) {
         if (!(actual < expected)) {
             fail(what + ": expected less than " + expected * 100 + "%, but got " + actual * 100
                     + "%; " + hint);
         }
     }

     private void requestLightBars(final int background) throws Throwable {
         final LightBarActivity activity = mActivityRule.getActivity();
         activity.runOnUiThread(() -> {
             activity.getWindow().setStatusBarColor(background);
             activity.getWindow().setNavigationBarColor(background);
             activity.setLightStatusBar(true);
             activity.setLightNavigationBar(true);
         });
     }

     private static class Stats {
         int backgroundPixels;
         int iconPixels;
         int sameHueDarkPixels;
         int sameHueLightPixels;
         int unexpectedHuePixels;

         int totalPixels() {
             return backgroundPixels + iconPixels + sameHueDarkPixels
                     + sameHueLightPixels + unexpectedHuePixels;
         }

         int foregroundPixels() {
             return iconPixels + sameHueDarkPixels
                     + sameHueLightPixels + unexpectedHuePixels;
         }

         @Override
         public String toString() {
             return String.format("{bg=%d, ic=%d, dark=%d, light=%d, bad=%d}",
                     backgroundPixels, iconPixels, sameHueDarkPixels, sameHueLightPixels,
                     unexpectedHuePixels);
         }
     }

     private Stats evaluateLightBarBitmap(Bitmap bitmap, int background) {
         int iconColor = 0x99000000;
         int iconPartialColor = 0x3d000000;

         int mixedIconColor = mixSrcOver(background, iconColor);
         int mixedIconPartialColor = mixSrcOver(background, iconPartialColor);
         float [] hsvMixedIconColor = new float[3];
         float [] hsvMixedPartialColor = new float[3];
         Color.RGBToHSV(Color.red(mixedIconColor), Color.green(mixedIconColor),
                 Color.blue(mixedIconColor), hsvMixedIconColor);
         Color.RGBToHSV(Color.red(mixedIconPartialColor), Color.green(mixedIconPartialColor),
                 Color.blue(mixedIconPartialColor), hsvMixedPartialColor);

         float maxHsvValue = Math.max(hsvMixedIconColor[2], hsvMixedPartialColor[2]);
         float minHsvValue = Math.min(hsvMixedIconColor[2], hsvMixedPartialColor[2]);

         int[] pixels = new int[bitmap.getHeight() * bitmap.getWidth()];
         bitmap.getPixels(pixels, 0, bitmap.getWidth(), 0, 0, bitmap.getWidth(), bitmap.getHeight());

         Stats s = new Stats();
         float eps = 0.005f;

         float [] hsvPixel = new float[3];
         for (int c : pixels) {
             if (isColorSame(c, background)) {
                 s.backgroundPixels++;
                 continue;
             }

             // What we expect the icons to be colored according to the spec.
             Color.RGBToHSV(Color.red(c), Color.green(c), Color.blue(c), hsvPixel);
             if (isColorSame(c, mixedIconColor) || isColorSame(c, mixedIconPartialColor)
                     || (hsvPixel[2] >= minHsvValue && hsvPixel[2] <= maxHsvValue)) {
                 s.iconPixels++;
                 continue;
             }

             // Due to anti-aliasing, there will be deviations from the ideal icon color, but it
             // should still be mostly the same hue.
             float hueDiff = Math.abs(ColorUtils.hue(background) - ColorUtils.hue(c));
             if (hueDiff < eps || hueDiff > 1 - eps) {
                 // .. it shouldn't be lighter than the original background though.
                 if (ColorUtils.brightness(c) > ColorUtils.brightness(background)) {
                     s.sameHueLightPixels++;
                 } else {
                     s.sameHueDarkPixels++;
                 }
                 continue;
             }

             s.unexpectedHuePixels++;
         }

         return s;
     }

     private int mixSrcOver(int background, int foreground) {
         int bgAlpha = Color.alpha(background);
         int bgRed = Color.red(background);
         int bgGreen = Color.green(background);
         int bgBlue = Color.blue(background);

         int fgAlpha = Color.alpha(foreground);
         int fgRed = Color.red(foreground);
         int fgGreen = Color.green(foreground);
         int fgBlue = Color.blue(foreground);

         return Color.argb(fgAlpha + (255 - fgAlpha) * bgAlpha / 255,
                     fgRed + (255 - fgAlpha) * bgRed / 255,
                     fgGreen + (255 - fgAlpha) * bgGreen / 255,
                     fgBlue + (255 - fgAlpha) * bgBlue / 255);
     }

     /**
      * Check if two colors' diff is in the error margin as defined in
      * {@link #COLOR_COMPONENT_ERROR_MARGIN}.
      */
     private boolean isColorSame(int c1, int c2){
         return Math.abs(Color.alpha(c1) - Color.alpha(c2)) < COLOR_COMPONENT_ERROR_MARGIN
                 && Math.abs(Color.red(c1) - Color.red(c2)) < COLOR_COMPONENT_ERROR_MARGIN
                 && Math.abs(Color.green(c1) - Color.green(c2)) < COLOR_COMPONENT_ERROR_MARGIN
                 && Math.abs(Color.blue(c1) - Color.blue(c2)) < COLOR_COMPONENT_ERROR_MARGIN;
     }
 }
	/*
	* Copyright (C) 2015 The Android Open Source Project
	*
	* 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 android.systemui.cts;

	import static android.support.test.InstrumentationRegistry.getInstrumentation;
	import static org.junit.Assert.assertTrue;
	import static org.junit.Assert.fail;

	import android.app.ActivityManager;
	import android.app.Notification;
	import android.app.NotificationChannel;
	import android.app.NotificationManager;
	import android.app.UiAutomation;
	import android.content.Context;
	import android.content.pm.PackageManager;
	import android.graphics.Bitmap;
	import android.graphics.Color;
	import android.os.SystemClock;
	import android.support.test.rule.ActivityTestRule;
	import android.support.test.runner.AndroidJUnit4;
	import android.view.InputDevice;
	import android.view.MotionEvent;

	import org.junit.Rule;
	import org.junit.Test;
	import org.junit.runner.RunWith;

	/**
	* Test for light status bar.
	*
	* atest CtsSystemUiTestCases:LightBarTests
	*/
	@RunWith(AndroidJUnit4.class)
	public class LightBarTests extends LightBarTestBase {

	public static final String TAG = "LightStatusBarTests";

	private static final int WAIT_TIME = 2000;

	/**
	* Color may be slightly off-spec when resources are resized for lower densities. Use this error
	* margin to accommodate for that when comparing colors.
	*/
	private static final int COLOR_COMPONENT_ERROR_MARGIN = 20;

	private final String NOTIFICATION_TAG = "TEST_TAG";
	private final String NOTIFICATION_CHANNEL_ID = "test_channel";
	private final String NOTIFICATION_GROUP_KEY = "test_group";
	private NotificationManager mNm;

	@Rule
	public ActivityTestRule<LightBarActivity> mActivityRule = new ActivityTestRule<>(
	LightBarActivity.class);

	@Test
	public void testLightStatusBarIcons() throws Throwable {
	assumeHasColoredStatusBar(mActivityRule);

	mNm = (NotificationManager) getInstrumentation().getContext()
	.getSystemService(Context.NOTIFICATION_SERVICE);
	NotificationChannel channel1 = new NotificationChannel(NOTIFICATION_CHANNEL_ID,
	NOTIFICATION_CHANNEL_ID, NotificationManager.IMPORTANCE_LOW);
	mNm.createNotificationChannel(channel1);

	// post 10 notifications to ensure enough icons in the status bar
	for (int i = 0; i < 10; i++) {
	Notification.Builder noti1 = new Notification.Builder(getInstrumentation().getContext(),
	NOTIFICATION_CHANNEL_ID)
	.setSmallIcon(R.drawable.ic_save)
	.setChannelId(NOTIFICATION_CHANNEL_ID)
	.setPriority(Notification.PRIORITY_LOW)
	.setGroup(NOTIFICATION_GROUP_KEY);
	mNm.notify(NOTIFICATION_TAG, i, noti1.build());
	}
	Thread.sleep(WAIT_TIME);
	Bitmap beforeBitmap = takeStatusBarScreenshot(mActivityRule.getActivity());

	requestLightBars(Color.RED /* background */);
	Thread.sleep(WAIT_TIME);

	Bitmap bitmap = takeStatusBarScreenshot(mActivityRule.getActivity());
	Bitmap result = treatCutoutAsBackground(beforeBitmap, bitmap);
	if (beforeBitmap != null) {
	beforeBitmap.recycle();
	}
	if (bitmap != null && bitmap != result) {
	bitmap.recycle();
	}

	Stats s = evaluateLightBarBitmap(result, Color.RED /* background */);
	assertLightStats(result, s);

	mNm.cancelAll();
	mNm.deleteNotificationChannel(NOTIFICATION_CHANNEL_ID);
	}

	private Bitmap treatCutoutAsBackground(Bitmap before, Bitmap after) {
	if (before == null \|\| after == null \|\| before.getWidth() != after.getWidth()
	\|\| before.getHeight() != after.getHeight()) {
	return after;
	}

	Bitmap result = after.copy(Bitmap.Config.ARGB_8888, true);

	final int width = before.getWidth();
	final int height = after.getHeight();
	int[] beforePixels = new int[height * width];
	before.getPixels(beforePixels, 0, width, 0, 0, width, height);
	int[] afterPixels = new int[height * width];
	after.getPixels(afterPixels, 0, width, 0, 0, width, height);

	for (int i = 0; i < height; i++) {
	for (int j = 0; j < width; j++) {
	int cBefore = beforePixels[i * width + j];
	int cAfter = afterPixels[i * width + j];

	if (cBefore == cAfter && Color.luminance(cAfter) < 0.01f) {
	result.setPixel(j, i, Color.RED);
	}
	}
	}

	return result;
	}

	@Test
	public void testLightNavigationBar() throws Throwable {
	assumeHasColorNavigationBar(mActivityRule);

	requestLightBars(Color.RED /* background */);
	Thread.sleep(WAIT_TIME);

	// Inject a cancelled interaction with the nav bar to ensure it is at full opacity.
	int x = mActivityRule.getActivity().getWidth() / 2;
	int y = mActivityRule.getActivity().getBottom() + 10;
	injectCanceledTap(x, y);
	Thread.sleep(WAIT_TIME);

	Bitmap bitmap = takeNavigationBarScreenshot(mActivityRule.getActivity());
	Stats s = evaluateLightBarBitmap(bitmap, Color.RED /* background */);
	assertLightStats(bitmap, s);
	}

	private void injectCanceledTap(int x, int y) {
	long downTime = SystemClock.uptimeMillis();
	injectEvent(MotionEvent.ACTION_DOWN, x, y, downTime);
	injectEvent(MotionEvent.ACTION_CANCEL, x, y, downTime);
	}

	private void injectEvent(int action, int x, int y, long downTime) {
	final UiAutomation automation = getInstrumentation().getUiAutomation();
	final long eventTime = SystemClock.uptimeMillis();
	MotionEvent event = MotionEvent.obtain(downTime, eventTime, action, x, y, 0);
	event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
	assertTrue(automation.injectInputEvent(event, true));
	event.recycle();
	}

	private void assertLightStats(Bitmap bitmap, Stats s) {
	boolean success = false;
	try {
	assertMoreThan("Not enough background pixels", 0.3f,
	(float) s.backgroundPixels / s.totalPixels(),
	"Is the bar background showing correctly (solid red)?");

	assertMoreThan("Not enough pixels colored as in the spec", 0.3f,
	(float) s.iconPixels / s.foregroundPixels(),
	"Are the bar icons colored according to the spec "
	+ "(60% black and 24% black)?");

	assertLessThan("Too many lighter pixels lighter than the background", 0.05f,
	(float) s.sameHueLightPixels / s.foregroundPixels(),
	"Are the bar icons dark?");

	assertLessThan("Too many pixels with a changed hue", 0.05f,
	(float) s.unexpectedHuePixels / s.foregroundPixels(),
	"Are the bar icons color-free?");

	success = true;
	} finally {
	if (!success) {
	dumpBitmap(bitmap);
	}
	}
	}

	private void assertMoreThan(String what, float expected, float actual, String hint) {
	if (!(actual > expected)) {
	fail(what + ": expected more than " + expected * 100 + "%, but only got " + actual * 100
	+ "%; " + hint);
	}
	}

	private void assertLessThan(String what, float expected, float actual, String hint) {
	if (!(actual < expected)) {
	fail(what + ": expected less than " + expected * 100 + "%, but got " + actual * 100
	+ "%; " + hint);
	}
	}

	private void requestLightBars(final int background) throws Throwable {
	final LightBarActivity activity = mActivityRule.getActivity();
	activity.runOnUiThread(() -> {
	activity.getWindow().setStatusBarColor(background);
	activity.getWindow().setNavigationBarColor(background);
	activity.setLightStatusBar(true);
	activity.setLightNavigationBar(true);
	});
	}

	private static class Stats {
	int backgroundPixels;
	int iconPixels;
	int sameHueDarkPixels;
	int sameHueLightPixels;
	int unexpectedHuePixels;

	int totalPixels() {
	return backgroundPixels + iconPixels + sameHueDarkPixels
	+ sameHueLightPixels + unexpectedHuePixels;
	}

	int foregroundPixels() {
	return iconPixels + sameHueDarkPixels
	+ sameHueLightPixels + unexpectedHuePixels;
	}

	@Override
	public String toString() {
	return String.format("{bg=%d, ic=%d, dark=%d, light=%d, bad=%d}",
	backgroundPixels, iconPixels, sameHueDarkPixels, sameHueLightPixels,
	unexpectedHuePixels);
	}
	}

	private Stats evaluateLightBarBitmap(Bitmap bitmap, int background) {
	int iconColor = 0x99000000;
	int iconPartialColor = 0x3d000000;

	int mixedIconColor = mixSrcOver(background, iconColor);
	int mixedIconPartialColor = mixSrcOver(background, iconPartialColor);
	float [] hsvMixedIconColor = new float[3];
	float [] hsvMixedPartialColor = new float[3];
	Color.RGBToHSV(Color.red(mixedIconColor), Color.green(mixedIconColor),
	Color.blue(mixedIconColor), hsvMixedIconColor);
	Color.RGBToHSV(Color.red(mixedIconPartialColor), Color.green(mixedIconPartialColor),
	Color.blue(mixedIconPartialColor), hsvMixedPartialColor);

	float maxHsvValue = Math.max(hsvMixedIconColor[2], hsvMixedPartialColor[2]);
	float minHsvValue = Math.min(hsvMixedIconColor[2], hsvMixedPartialColor[2]);

	int[] pixels = new int[bitmap.getHeight() * bitmap.getWidth()];
	bitmap.getPixels(pixels, 0, bitmap.getWidth(), 0, 0, bitmap.getWidth(), bitmap.getHeight());

	Stats s = new Stats();
	float eps = 0.005f;

	float [] hsvPixel = new float[3];
	for (int c : pixels) {
	if (isColorSame(c, background)) {
	s.backgroundPixels++;
	continue;
	}

	// What we expect the icons to be colored according to the spec.
	Color.RGBToHSV(Color.red(c), Color.green(c), Color.blue(c), hsvPixel);
	if (isColorSame(c, mixedIconColor) \|\| isColorSame(c, mixedIconPartialColor)
	\|\| (hsvPixel[2] >= minHsvValue && hsvPixel[2] <= maxHsvValue)) {
	s.iconPixels++;
	continue;
	}

	// Due to anti-aliasing, there will be deviations from the ideal icon color, but it
	// should still be mostly the same hue.
	float hueDiff = Math.abs(ColorUtils.hue(background) - ColorUtils.hue(c));
	if (hueDiff < eps \|\| hueDiff > 1 - eps) {
	// .. it shouldn't be lighter than the original background though.
	if (ColorUtils.brightness(c) > ColorUtils.brightness(background)) {
	s.sameHueLightPixels++;
	} else {
	s.sameHueDarkPixels++;
	}
	continue;
	}

	s.unexpectedHuePixels++;
	}

	return s;
	}

	private int mixSrcOver(int background, int foreground) {
	int bgAlpha = Color.alpha(background);
	int bgRed = Color.red(background);
	int bgGreen = Color.green(background);
	int bgBlue = Color.blue(background);

	int fgAlpha = Color.alpha(foreground);
	int fgRed = Color.red(foreground);
	int fgGreen = Color.green(foreground);
	int fgBlue = Color.blue(foreground);

	return Color.argb(fgAlpha + (255 - fgAlpha) * bgAlpha / 255,
	fgRed + (255 - fgAlpha) * bgRed / 255,
	fgGreen + (255 - fgAlpha) * bgGreen / 255,
	fgBlue + (255 - fgAlpha) * bgBlue / 255);
	}

	/**
	* Check if two colors' diff is in the error margin as defined in
	* {@link #COLOR_COMPONENT_ERROR_MARGIN}.
	*/
	private boolean isColorSame(int c1, int c2){
	return Math.abs(Color.alpha(c1) - Color.alpha(c2)) < COLOR_COMPONENT_ERROR_MARGIN
	&& Math.abs(Color.red(c1) - Color.red(c2)) < COLOR_COMPONENT_ERROR_MARGIN
	&& Math.abs(Color.green(c1) - Color.green(c2)) < COLOR_COMPONENT_ERROR_MARGIN
	&& Math.abs(Color.blue(c1) - Color.blue(c2)) < COLOR_COMPONENT_ERROR_MARGIN;
	}
	}