Size of laplacian pyramid?

[tuanhanhdmprof]

Hello everyone,
I have a question about the size of the laplacian pyramid.
According to the specification of the khronos, the Laplacian level Li is computed as:

Li = Gi - UpSample(Gi+1). (1)

UpSample(I) is computed by injecting even zero rows and columns and then convolves the result with the Gaussian 5x5 filter multiplied by 4.

After upsample, size of image is 2 times the original size. But to create Gi+1 we need to downsample using VX_INTERPOLATION_NEAREST_NEIGHBOR. After downsample, size of downsample image is ceil(size of prev image * scale).

For example, i have an image 9x9:

• Apply gaussian and downsample: ceil(9x9 * 0.5) = 5x5
• Apply laplacian: 5x5 *2 = 10x10.

In fomula 1, Gi has size 9x9, upsample(gi+1) has size 10x10
so how much will Li have? (9x9 or 10x10)