Original picture
1. First, open the original image and draw a selection of transparent objects. Press Ctrl+J again to copy the effects wheel to a new layer, and then hide the background layer.
2. Next go to the channel panel, press Ctrl and click on the RGB channel, load the selection, and create a new channel Alpha1.
3. Press Ctrl+Shift+I to invert the selection and fill it with white.
4. Press Ctrl+D to cancel the selection, go to the layer panel and create a new layer (layer 2), fill it with black, move it below the plate layer (layer 1), then observe the light and dark relationship of each channel, and then copy the blue color channel.
