Super simple method to cut out a wedding dress

Original picture

final renderings
Step 1: Open the original image, create three new layers, and set the mode to Screen.

Step 2: Open the channel panel and load the bright and dark channels.

Step 3: Fill in pure red, green and blue colors respectively, click the link and merge the three layers.

Step 4: Drag in the landscape (layer four), copy the person (background layer) to the top, and set the mode to Screen. Duplicate the person (background layer) again, put it on top, and add a mask. Use a brush to erase the new background and transparent wedding dress on the mask, and it's done.