Android How to - Get Bitmap Thumbnail

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Question

We would like to know how to get Bitmap Thumbnail.

Answer

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
// w  w  w .  ja  v a2s .  c  o m
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;

public class Main {
    public static Bitmap getThumbnail(Context context, Uri uri, int size)
            throws FileNotFoundException, IOException {
        InputStream input = context.getContentResolver().openInputStream(uri);

        BitmapFactory.Options onlyBoundsOptions = new BitmapFactory.Options();
        onlyBoundsOptions.inJustDecodeBounds = true;
        onlyBoundsOptions.inDither = true;// optional
        onlyBoundsOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;// optional
        BitmapFactory.decodeStream(input, null, onlyBoundsOptions);
        input.close();
        if ((onlyBoundsOptions.outWidth == -1) || (onlyBoundsOptions.outHeight == -1))
            return null;

        int originalSize = (onlyBoundsOptions.outHeight > onlyBoundsOptions.outWidth) ? onlyBoundsOptions.outHeight
                : onlyBoundsOptions.outWidth;

        double ratio = (originalSize > size) ? (originalSize / size) : 1.0;

        BitmapFactory.Options bitmapOptions = new BitmapFactory.Options();
        bitmapOptions.inSampleSize = getPowerOfTwoForSampleRatio(ratio);
        bitmapOptions.inDither = true;// optional
        bitmapOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;// optional
        input = context.getContentResolver().openInputStream(uri);
        Bitmap bitmap = BitmapFactory.decodeStream(input, null, bitmapOptions);
        input.close();
        return bitmap;
    }
    private static int getPowerOfTwoForSampleRatio(double ratio) {
        int k = Integer.highestOneBit((int) Math.floor(ratio));
        if (k == 0)
            return 1;
        else
            return k;
    }
}

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