以下方法是拼接两个Bitmap的方法；
但发现这个方法生成的位图背景色为黑色。
原因是 Bitmap.Config.RGB_565；
若要使背景为透明，必须设置为Config.ARGB_4444，或者Config.ARGB_8888， 而不是Bitmap.Config.RGB_565。

/**
 * 把两个位图覆盖合成为一个位图，上下拼接
 *
 * @param topBitmap
 * @param bottomBitmap
 * @param isBaseMax    是否以高度大的位图为准，true则小图等比拉伸，false则大图等比压缩
 * @return
 */
public static Bitmap mergeBitmap_TB(Bitmap topBitmap, Bitmap bottomBitmap, boolean isBaseMax) {

    if (topBitmap == null || topBitmap.isRecycled()
            || bottomBitmap == null || bottomBitmap.isRecycled()) {
        return null;
    }
    int width = 0;
    if (isBaseMax) {
        width = topBitmap.getWidth() > bottomBitmap.getWidth() ? topBitmap.getWidth() : bottomBitmap.getWidth();
    } else {
        width = topBitmap.getWidth() < bottomBitmap.getWidth() ? topBitmap.getWidth() : bottomBitmap.getWidth();
    }
    Bitmap tempBitmapT = topBitmap;
    Bitmap tempBitmapB = bottomBitmap;

    if (topBitmap.getWidth() != width) {
        tempBitmapT = Bitmap.createScaledBitmap(topBitmap, width, (int) (topBitmap.getHeight() * 1f / topBitmap.getWidth() * width), false);
    } else if (bottomBitmap.getWidth() != width) {
        tempBitmapB = Bitmap.createScaledBitmap(bottomBitmap, width, (int) (bottomBitmap.getHeight() * 1f / bottomBitmap.getWidth() * width), false);
    }

    int height = tempBitmapT.getHeight() + tempBitmapB.getHeight();
    Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(bitmap);
    Rect topRect = new Rect(0, 0, tempBitmapT.getWidth(), tempBitmapT.getHeight());
    Rect bottomRect = new Rect(0, 0, tempBitmapB.getWidth(), tempBitmapB.getHeight());
    Rect bottomRectT = new Rect(0, tempBitmapT.getHeight(), width, height);
    canvas.drawBitmap(tempBitmapT, topRect, topRect, null);
    canvas.drawBitmap(tempBitmapB, bottomRect, bottomRectT, null);
    return bitmap;
}