フォトショップスケッチで二階調ペンや真っ白の用紙はありますか？

Hi.

I'm sorry, no, there are no two-tone brushes in Sketch, but you could create one in ‎Adobe Capture on the App Store and use it in Sketch.

I'm not sure which version of the app you're using but if you're using Sketch for iOS, you can just double-tap the Background Layer,  bottom-most layer, in the layer thumbnail stack, and when you can see an eye icon with a slash through it that will save the art with a transparent background.

I hope that helps. Please let me know if I can answer any other questions.

Sue.