ImageView personalizado con sombra paralela

Esto está tomado de la presentación de Romain Guy en Devoxx, pdf encontrado aquí.

Paint mShadow = new Paint(); 
// radius=10, y-offset=2, color=black 
mShadow.setShadowLayer(10.0f, 0.0f, 2.0f, 0xFF000000); 
// in onDraw(Canvas) 
canvas.drawBitmap(bitmap, 0.0f, 0.0f, mShadow);

Espero que esto ayude.

NOTAS

1. No olvides que para Honeycomb y superior necesitas invocar setLayerType(LAYER_TYPE_SOFTWARE, mShadow), de lo contrario no verás tu sombra! (@Dmitriy_Boichenko)
2. SetShadowLayer hace no funciona con aceleración de hardware por desgracia, por lo que en gran medida reduce el rendimiento (@Matt Wear) [1] [2]

Creo que esta respuesta de UIFuel

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

     <!-- Drop Shadow Stack -->
     <item>
        <shape>
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#00CCCCCC" />
        </shape>
    </item>
     <item>
        <shape>
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#10CCCCCC" />
        </shape>
    </item>
     <item>
        <shape>
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#20CCCCCC" />
        </shape>
    </item>
     <item>
        <shape>
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#30CCCCCC" />
        </shape>
    </item>
    <item>
        <shape>
            <padding android:top="1dp" android:right="1dp" android:bottom="1dp" android:left="1dp" />
            <solid android:color="#50CCCCCC" />
        </shape>
    </item>

    <!-- Background -->
    <item>
    <shape>
            <solid android:color="@color/white" />
        <corners android:radius="3dp" />
    </shape>
    </item>
</layer-list>

Mi solución sucia:

private static Bitmap getDropShadow3(Bitmap bitmap) {

    if (bitmap==null) return null;
    int think = 6;
    int w = bitmap.getWidth();
    int h = bitmap.getHeight();

    int newW = w - (think);
    int newH = h - (think);

    Bitmap.Config conf = Bitmap.Config.ARGB_8888;
    Bitmap bmp = Bitmap.createBitmap(w, h, conf);
    Bitmap sbmp = Bitmap.createScaledBitmap(bitmap, newW, newH, false);

    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    Canvas c = new Canvas(bmp);

    // Right
    Shader rshader = new LinearGradient(newW, 0, w, 0, Color.GRAY, Color.LTGRAY, Shader.TileMode.CLAMP);
    paint.setShader(rshader);
    c.drawRect(newW, think, w, newH, paint);

    // Bottom
    Shader bshader = new LinearGradient(0, newH, 0, h, Color.GRAY, Color.LTGRAY, Shader.TileMode.CLAMP);
    paint.setShader(bshader);
    c.drawRect(think, newH, newW  , h, paint);

    //Corner
    Shader cchader = new LinearGradient(0, newH, 0, h, Color.LTGRAY, Color.LTGRAY, Shader.TileMode.CLAMP);
    paint.setShader(cchader);
    c.drawRect(newW, newH, w  , h, paint);


    c.drawBitmap(sbmp, 0, 0, null);

    return bmp;
}

Resultado:

Aquí estás. Establezca el origen de ImageView estáticamente en xml o dinámicamente en código.

La sombra está aquí blanca.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content" android:layout_height="wrap_content">

    <View android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:background="@android:color/white" android:layout_alignLeft="@+id/image"
        android:layout_alignRight="@id/image" android:layout_alignTop="@id/image"
        android:layout_alignBottom="@id/image" android:layout_marginLeft="10dp"
        android:layout_marginBottom="10dp" />

    <ImageView android:id="@id/image" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:src="..."
        android:padding="5dp" />

</RelativeLayout>

Me las arreglo para aplicar el borde degradado usando este código..

public static Bitmap drawShadow(Bitmap bitmap, int leftRightThk, int bottomThk, int padTop) {
    int w = bitmap.getWidth();
    int h = bitmap.getHeight();

    int newW = w - (leftRightThk * 2);
    int newH = h - (bottomThk + padTop);

    Bitmap.Config conf = Bitmap.Config.ARGB_8888;
    Bitmap bmp = Bitmap.createBitmap(w, h, conf);
    Bitmap sbmp = Bitmap.createScaledBitmap(bitmap, newW, newH, false);

    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    Canvas c = new Canvas(bmp);

    // Left
    int leftMargin = (leftRightThk + 7)/2;
    Shader lshader = new LinearGradient(0, 0, leftMargin, 0, Color.TRANSPARENT, Color.BLACK, TileMode.CLAMP);
    paint.setShader(lshader);
    c.drawRect(0, padTop, leftMargin, newH, paint); 

    // Right
    Shader rshader = new LinearGradient(w - leftMargin, 0, w, 0, Color.BLACK, Color.TRANSPARENT, TileMode.CLAMP);
    paint.setShader(rshader);
    c.drawRect(newW, padTop, w, newH, paint);

    // Bottom
    Shader bshader = new LinearGradient(0, newH, 0, bitmap.getHeight(), Color.BLACK, Color.TRANSPARENT, TileMode.CLAMP);
    paint.setShader(bshader);
    c.drawRect(leftMargin -3, newH, newW + leftMargin + 3, bitmap.getHeight(), paint);
    c.drawBitmap(sbmp, leftRightThk, 0, null);

    return bmp;
}

Espero que esto ayude !

Esto funciona para mí ...

public class ShadowImage extends Drawable {

Bitmap bm;

@Override
public void draw(Canvas canvas) {

    Paint mShadow = new Paint();
    Rect rect = new Rect(0,0,bm.getWidth(), bm.getHeight());

    mShadow.setAntiAlias(true);
    mShadow.setShadowLayer(5.5f, 4.0f, 4.0f, Color.BLACK);

    canvas.drawRect(rect, mShadow);
    canvas.drawBitmap(bm, 0.0f, 0.0f, null);

}

public ShadowImage(Bitmap bitmap) {
    super();
    this.bm = bitmap;
} ... }

Aquí la Implementación dela respuesta de Paul Burke :

public class ShadowImageView extends ImageView {

    public ShadowImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public ShadowImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public ShadowImageView(Context context) {
        super(context);
    }

    private Paint createShadow() {
        Paint mShadow = new Paint();

        float radius = 10.0f;
        float xOffset = 0.0f;
        float yOffset = 2.0f;

        // color=black
        int color = 0xFF000000;
        mShadow.setShadowLayer(radius, xOffset, yOffset, color);


        return mShadow;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        Paint mShadow = createShadow();
        Drawable d = getDrawable();
        if (d != null){
            setLayerType(LAYER_TYPE_SOFTWARE, mShadow);
            Bitmap bitmap = ((BitmapDrawable) getDrawable()).getBitmap();
            canvas.drawBitmap(bitmap, 0.0f, 0.0f, mShadow);
        } else {
            super.onDraw(canvas);
        }

    };

}

TODO: ejecutar setLayerType(LAYER_TYPE_SOFTWARE, mShadow); solo si el nivel de API es > 10

He construido sobre la respuesta anterior - https://stackoverflow.com/a/11155031/2060486 - para crear una sombra alrededor de TODOS los lados..

 private static final int GRAY_COLOR_FOR_SHADE = Color.argb(50, 79, 79, 79);

// this method takes a bitmap and draws around it 4 rectangles with gradient to create a
// shadow effect.
public static Bitmap addShadowToBitmap(Bitmap origBitmap) {
    int shadowThickness = 13; // can be adjusted as needed
    int bmpOriginalWidth = origBitmap.getWidth();
    int bmpOriginalHeight = origBitmap.getHeight();
    int bigW = bmpOriginalWidth + shadowThickness * 2; // getting dimensions for a bigger bitmap with margins
    int bigH = bmpOriginalHeight + shadowThickness * 2;
    Bitmap containerBitmap = Bitmap.createBitmap(bigW, bigH, Bitmap.Config.ARGB_8888);
    Bitmap copyOfOrigBitmap = Bitmap.createScaledBitmap(origBitmap, bmpOriginalWidth, bmpOriginalHeight, false);
    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    Canvas canvas = new Canvas(containerBitmap); // drawing the shades on the bigger bitmap
    //right shade - direction of gradient is positive x (width)
    Shader rightShader = new LinearGradient(bmpOriginalWidth, 0, bigW, 0, GRAY_COLOR_FOR_SHADE,
            Color.TRANSPARENT, Shader.TileMode.CLAMP);
    paint.setShader(rightShader);
    canvas.drawRect(bigW - shadowThickness, shadowThickness, bigW, bigH - shadowThickness, paint);
    //bottom shade - direction is positive y (height)
    Shader bottomShader = new LinearGradient(0, bmpOriginalHeight, 0, bigH, GRAY_COLOR_FOR_SHADE,
            Color.TRANSPARENT, Shader.TileMode.CLAMP);
    paint.setShader(bottomShader);
    canvas.drawRect(shadowThickness, bigH - shadowThickness, bigW - shadowThickness, bigH, paint);
    //left shade - direction is negative x
    Shader leftShader = new LinearGradient(shadowThickness, 0, 0, 0, GRAY_COLOR_FOR_SHADE,
            Color.TRANSPARENT, Shader.TileMode.CLAMP);
    paint.setShader(leftShader);
    canvas.drawRect(0, shadowThickness, shadowThickness, bigH - shadowThickness, paint);
    //top shade - direction is negative y
    Shader topShader = new LinearGradient(0, shadowThickness, 0, 0, GRAY_COLOR_FOR_SHADE,
            Color.TRANSPARENT, Shader.TileMode.CLAMP);
    paint.setShader(topShader);
    canvas.drawRect(shadowThickness, 0, bigW - shadowThickness, shadowThickness, paint);
    // starting to draw bitmap not from 0,0 to get margins for shade rectangles
    canvas.drawBitmap(copyOfOrigBitmap, shadowThickness, shadowThickness, null);
    return containerBitmap;
}

Cambie el color de la const como mejor le parezca.

Utilice esta clase para dibujar sombras en mapas de bits

public class ShadowGenerator {

    // Percent of actual icon size
    private static final float HALF_DISTANCE = 0.5f;
    public static final float BLUR_FACTOR = 0.5f/48;

    // Percent of actual icon size
    private static final float KEY_SHADOW_DISTANCE = 1f/48;
    public static final int KEY_SHADOW_ALPHA = 61;

    public static final int AMBIENT_SHADOW_ALPHA = 30;

    private static final Object LOCK = new Object();
    // Singleton object guarded by {@link #LOCK}
    private static ShadowGenerator sShadowGenerator;

    private  int mIconSize;

    private final Canvas mCanvas;
    private final Paint mBlurPaint;
    private final Paint mDrawPaint;
    private final Context mContext;

    private ShadowGenerator(Context context) {
        mContext = context;
        mIconSize = Utils.convertDpToPixel(context,63);
        mCanvas = new Canvas();
        mBlurPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);
        mBlurPaint.setMaskFilter(new BlurMaskFilter(mIconSize * BLUR_FACTOR, Blur.NORMAL));
        mDrawPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG);
    }

    public synchronized Bitmap recreateIcon(Bitmap icon) {
        mIconSize = Utils.convertDpToPixel(mContext,3)+icon.getWidth();
        int[] offset = new int[2];
        Bitmap shadow = icon.extractAlpha(mBlurPaint, offset);
        Bitmap result = Bitmap.createBitmap(mIconSize, mIconSize, Config.ARGB_8888);
        mCanvas.setBitmap(result);

        // Draw ambient shadow
        mDrawPaint.setAlpha(AMBIENT_SHADOW_ALPHA);
        mCanvas.drawBitmap(shadow, offset[0], offset[1], mDrawPaint);

        // Draw key shadow
        mDrawPaint.setAlpha(KEY_SHADOW_ALPHA);
        mCanvas.drawBitmap(shadow, offset[0], offset[1] + KEY_SHADOW_DISTANCE * mIconSize, mDrawPaint);

        // Draw the icon
        mDrawPaint.setAlpha(255);
        mCanvas.drawBitmap(icon, 0, 0, mDrawPaint);

        mCanvas.setBitmap(null);
        return result;
    }



    public static ShadowGenerator getInstance(Context context) {

        synchronized (LOCK) {
            if (sShadowGenerator == null) {
                sShadowGenerator = new ShadowGenerator(context);
            }
        }
        return sShadowGenerator;
    }

}