The generator seems didn't use "mask" information.

[penguinbing]

As the title said. Thank you.

[abtExp]

It does use the mask, the x (input) is a combination of the sketch, color, noise, mask and masked image.
The generator produces the completed image which is then multiplied with the mask to obtain only the masked portion from the generated image and the unmasked image is kept the same, thus reducing the noise introduced by the generator.

[penguinbing]

Thank you very much. The generator input parameters were misleading.