android根据原图片的路径得到该图片的缩略图

/**
     * 根据图片的路径得到该图片在表中的ID
     * @param cr
     * @param fileName
     * @return
     */
    public static String getImageIdFromPath(ContentResolver cr, String fileName) {

        //select condition.
        String whereClause = MediaStore.Images.Media.DATA + " = '" + fileName + "'";

        //colection of results.
        Cursor cursor = cr.query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, new String[]{MediaStore.Images.Media._ID}, whereClause, null, null);
        if (cursor == null || cursor.getCount() == 0) {
            if (cursor != null)
                cursor.close();
            return null;
        }
        cursor.moveToFirst();
        //image id in image table.
        String imageId = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media._ID));
        cursor.close();
        if (imageId == null) {
            return null;
        }
        return imageId;
    }

    /**
     * 根据图片的ID得到缩略图
     * @param cr
     * @param imageId
     * @return
     */
    public static Bitmap getThumbnailsFromImageId(ContentResolver cr, String imageId) {
        if (imageId == null || imageId.equals(""))
            return null;

        Bitmap bitmap = null;
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inDither = false;
        options.inPreferredConfig = Bitmap.Config.ARGB_8888;

        long imageIdLong = Long.parseLong(imageId);
        //via imageid get the bimap type thumbnail in thumbnail table.
        bitmap = MediaStore.Images.Thumbnails.getThumbnail(cr, imageIdLong, MediaStore.Images.Thumbnails.MINI_KIND, options);

        return bitmap;
    }