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Commit c4bbdff6 authored by Vinit Nayak's avatar Vinit Nayak
Browse files

Use median instead of mean for sampling border luma 

Using median of the luma for all border pixels
gives a more accurate indication of dominant
background color to use during the screen
rotation animation than does using the average.

fixes: 150056201
Test: Existing tests pass
Also can visually see the change in Google
Photos app where you have a bright image on
the black background. Now background stays
as black instead of being gray.

Change-Id: I87bc87930aff48f90f271fc1783e70caf61dc7f4
parent 0b66590f

services/core/java/com/android/server/wm/ScreenRotationAnimation.java

+1 −1
Original line number Diff line number Diff line
@@ -205,7 +205,7 @@ class ScreenRotationAnimation { 
            SurfaceControl.ScreenshotGraphicBuffer gb =

                    mService.mDisplayManagerInternal.screenshot(displayId);

            if (gb != null) {

                mStartLuma = RotationAnimationUtils.getAvgBorderLuma(gb.getGraphicBuffer(),

                mStartLuma = RotationAnimationUtils.getMedianBorderLuma(gb.getGraphicBuffer(),

                        gb.getColorSpace());

                try {

                    surface.attachAndQueueBufferWithColorSpace(gb.getGraphicBuffer(),

services/core/java/com/android/server/wm/utils/RotationAnimationUtils.java

+17 −11
Original line number Diff line number Diff line
@@ -26,6 +26,8 @@ import android.view.Display; 
import android.view.Surface;

import android.view.SurfaceControl;



import java.util.Arrays;





/** Helper functions for the {@link com.android.server.wm.ScreenRotationAnimation} class*/

public class RotationAnimationUtils {
@@ -35,31 +37,35 @@ public class RotationAnimationUtils { 
     * luminance at the borders of the bitmap

     * @return the average luminance of all the pixels at the borders of the bitmap

     */

    public static float getAvgBorderLuma(GraphicBuffer graphicBuffer, ColorSpace colorSpace) {

    public static float getMedianBorderLuma(GraphicBuffer graphicBuffer, ColorSpace colorSpace) {

        Bitmap hwBitmap = Bitmap.wrapHardwareBuffer(graphicBuffer, colorSpace);

        if (hwBitmap == null) {

            return 0;

        }



        Bitmap swaBitmap = hwBitmap.copy(Bitmap.Config.ARGB_8888, false);

        float totalLuma = 0;

        int height = swaBitmap.getHeight();

        int width = swaBitmap.getWidth();

        float[] borderLumas = new float[2 * width + 2 * height];

        int i;

        for (i = 0; i < width; i++) {

            totalLuma += swaBitmap.getColor(i, 0).luminance();

            totalLuma += swaBitmap.getColor(i, height - 1).luminance();

        int index = 0;

        for (i = 0; i < width; i++, index += 2) {

            borderLumas[index] = swaBitmap.getColor(i, 0).luminance();

            borderLumas[index + 1] = swaBitmap.getColor(i, height - 1).luminance();

        }

        for (i = 0; i < height; i++) {

            totalLuma += swaBitmap.getColor(0, i).luminance();

            totalLuma += swaBitmap.getColor(width - 1, i).luminance();

        for (i = 0; i < height; i++, index += 2) {

            borderLumas[index] = swaBitmap.getColor(0, i).luminance();

            borderLumas[index + 1] = swaBitmap.getColor(width - 1, i).luminance();

        }

        return totalLuma / (2 * width + 2 * height);

        // Oh, is this too simple and inefficient for you?

        // How about implementing a O(n) solution? https://en.wikipedia.org/wiki/Median_of_medians

        Arrays.sort(borderLumas);

        return borderLumas[borderLumas.length / 2];

    }



    /**

     * Gets the average border luma by taking a screenshot of the {@param surfaceControl}.

     * @see #getAvgBorderLuma(GraphicBuffer, ColorSpace)

     * @see #getMedianBorderLuma(GraphicBuffer, ColorSpace)

     */

    public static float getLumaOfSurfaceControl(Display display, SurfaceControl surfaceControl) {

        if (surfaceControl ==  null) {
@@ -75,7 +81,7 @@ public class RotationAnimationUtils { 
            return 0;

        }



        return RotationAnimationUtils.getAvgBorderLuma(buffer.getGraphicBuffer(),

        return RotationAnimationUtils.getMedianBorderLuma(buffer.getGraphicBuffer(),

                buffer.getColorSpace());

    }

services/tests/wmtests/src/com/android/server/wm/utils/RotationAnimationUtilsTest.java

+19 −7
Original line number Diff line number Diff line
@@ -50,7 +50,7 @@ public class RotationAnimationUtilsTest { 
    public void blackLuma() {

        Bitmap swBitmap = createBitmap(0);

        GraphicBuffer gb = swBitmapToGraphicsBuffer(swBitmap);

        float borderLuma = RotationAnimationUtils.getAvgBorderLuma(gb, mColorSpace);

        float borderLuma = RotationAnimationUtils.getMedianBorderLuma(gb, mColorSpace);

        assertEquals(0, borderLuma, 0);

    }
@@ -58,7 +58,15 @@ public class RotationAnimationUtilsTest { 
    public void whiteLuma() {

        Bitmap swBitmap = createBitmap(1);

        GraphicBuffer gb = swBitmapToGraphicsBuffer(swBitmap);

        float borderLuma = RotationAnimationUtils.getAvgBorderLuma(gb, mColorSpace);

        float borderLuma = RotationAnimationUtils.getMedianBorderLuma(gb, mColorSpace);

        assertEquals(1, borderLuma, 0);

    }



    @Test

    public void unevenBitmapDimens() {

        Bitmap swBitmap = createBitmap(1, BITMAP_WIDTH + 1, BITMAP_HEIGHT + 1);

        GraphicBuffer gb = swBitmapToGraphicsBuffer(swBitmap);

        float borderLuma = RotationAnimationUtils.getMedianBorderLuma(gb, mColorSpace);

        assertEquals(1, borderLuma, 0);

    }
@@ -67,7 +75,7 @@ public class RotationAnimationUtilsTest { 
        Bitmap swBitmap = createBitmap(1);

        setBorderLuma(swBitmap, 0);

        GraphicBuffer gb = swBitmapToGraphicsBuffer(swBitmap);

        float borderLuma = RotationAnimationUtils.getAvgBorderLuma(gb, mColorSpace);

        float borderLuma = RotationAnimationUtils.getMedianBorderLuma(gb, mColorSpace);

        assertEquals(0, borderLuma, 0);

    }
@@ -76,7 +84,7 @@ public class RotationAnimationUtilsTest { 
        Bitmap swBitmap = createBitmap(0);

        setBorderLuma(swBitmap, 1);

        GraphicBuffer gb = swBitmapToGraphicsBuffer(swBitmap);

        float borderLuma = RotationAnimationUtils.getAvgBorderLuma(gb, mColorSpace);

        float borderLuma = RotationAnimationUtils.getMedianBorderLuma(gb, mColorSpace);

        assertEquals(1, borderLuma, 0);

    }
@@ -123,9 +131,13 @@ public class RotationAnimationUtilsTest { 
    }



    private Bitmap createBitmap(float luma) {

        Bitmap bitmap = Bitmap.createBitmap(BITMAP_WIDTH, BITMAP_HEIGHT, ARGB_8888);

        for (int i = 0; i < BITMAP_WIDTH; i++) {

            for (int j = 0; j < BITMAP_HEIGHT; j++) {

        return createBitmap(luma, BITMAP_WIDTH, BITMAP_HEIGHT);

    }



    private Bitmap createBitmap(float luma, int width, int height) {

        Bitmap bitmap = Bitmap.createBitmap(width, height, ARGB_8888);

        for (int i = 0; i < width; i++) {

            for (int j = 0; j < height; j++) {

                bitmap.setPixel(i, j, Color.argb(1, luma, luma, luma));

            }

        }