I have not tested with other data types. Here is code:

<pre>
GpuMat dst;

Size s = Size(x, y);

if (gpu) {

gpu::resize(src, dst, s, 0, 0, INTER_CUBIC);

} else {

Mat m = Mat(src);

Mat m2;

resize(m, m2, s, 0, 0, INTER_CUBIC);

dst = GpuMat(m2);

}
</pre>

Resulting image have alpha applied at all image (i guess ~50%). If i do with cpu method image is ok.