android - 如何使图像透明android

Question

想我有一个从媒体商店的专辑封面加载的位图，它有 100% 的透明值，我怎样才能将其更改为 50 或 30？

另外，您知道我可以使图像变成黑白的任何方法吗？

谢谢

Answer 1

使用以下方法：

/**
 * @param bitmap The source bitmap.
 * @param opacity a value between 0 (completely transparent) and 255 (completely
 * opaque).
 * @return The opacity-adjusted bitmap.  If the source bitmap is mutable it will be
 * adjusted and returned, otherwise a new bitmap is created.
 */
private Bitmap adjustOpacity(Bitmap bitmap, int opacity)
{
    Bitmap mutableBitmap = bitmap.copy(Bitmap.Config.ARGB_8888, true);
    Canvas canvas = new Canvas(mutableBitmap);
    int colour = (opacity & 0xFF) << 24;
    canvas.drawColor(colour, PorterDuff.Mode.DST_IN);
    return mutableBitmap;
}

此处说明：http: //blog.uncommons.org/2011/01/12/adjusting-the-opacity-of-an-android-bitmap/

Answer 2

将 alpha 设置在 0 到 255 之间！！

alpha 设置为 45 将使图像透明

ViewName.getBackground().setAlpha(65);