Custom ImageView with drop shadow

Question

Okay, I've been reading and searching around, and am now banging my head against the wall trying to figure this out. Here's what I have so far:

package com.pockdroid.sandbox;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.widget.ImageView;

public class ShadowImageView extends ImageView {

private Rect mRect;
private Paint mPaint;

public ShadowImageView(Context context)
{
    super(context);
    mRect = new Rect();
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setShadowLayer(2f, 1f, 1f, Color.BLACK);
}

@Override
protected void onDraw(Canvas canvas) 
{
    Rect r = mRect;
    Paint paint = mPaint;

    canvas.drawRect(r, paint);
    super.onDraw(canvas);
}

@Override
protected void onMeasure(int w, int h)
{
    super.onMeasure(w,h);
    int mH, mW;
    mW = getSuggestedMinimumWidth() < getMeasuredWidth()? getMeasuredWidth() : getSuggestedMinimumWidth();
    mH = getSuggestedMinimumHeight() < getMeasuredHeight()? getMeasuredHeight() : getSuggestedMinimumHeight();
    setMeasuredDimension(mW + 5, mH + 5);
}

}

The "+5" in the measurements are there as temporary; From what I understand I'll need to do some math to determine the size that the drop shadow adds to the canvas, right?

But when I use this:

public View getView(int position, View convertView, ViewGroup parent) {
    ShadowImageView sImageView;
    if (convertView == null) {
        sImageView = new ShadowImageView(mContext);
        GridView.LayoutParams lp = new GridView.LayoutParams(85, 85);
        sImageView.setLayoutParams(lp);

        sImageView.setScaleType(ImageView.ScaleType.CENTER);
        sImageView.setPadding(5,5,5,5);
    } else {
        sImageView = (ShadowImageView) convertView;
    }

    sImageView.setImageBitmap(bitmapList.get(position));
    return sImageView;
}

in my ImageView, I still get just a normal ImageView when I run the program.

Any thoughts? Thanks.

EDIT: So I spoke with RomainGuy some in the IRC channel, and I have it working now for plain rectangular images with the below code. It still won't draw the shadow directly to my bitmap's transparency though, so I'm still working on that.

@Override
protected void onDraw(Canvas canvas) 
{
    Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.omen);
    Paint paint = new Paint();
    paint.setAntiAlias(true);
    paint.setShadowLayer(5.5f, 6.0f, 6.0f, Color.BLACK);
    canvas.drawColor(Color.GRAY);
    canvas.drawRect(50, 50, 50 + bmp.getWidth(), 50 + bmp.getHeight(), paint);
    canvas.drawBitmap(bmp, 50, 50, null);       
}

user_321697 · Answer

Okay, I don't foresee any more answers on this one, so what I ended up going with for now is just a solution for rectangular images. I've used the following NinePatch:

alt text

along with the appropriate padding in XML:

to get a fairly good result:

alt text

Not ideal, but it'll do.

user_1325942 · Answer

Use this class to draw shadow on bitmaps

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;
    }

}

user_6907714 · Answer

If you want to use the custom imageView, I suggest you use this one

View look perfect and dont't use any nine path image

Custom ImageView with drop shadow

11 Answers