The use of Photoshop masks (also called masks)

Mask, also known as mask. It is used to realize image transition or fusion.

The working principle is: to use a mask on a layer, it is to cover the layer with white or black: the part covered with pure white, fully displayed, and covered with pure black, transparent Display (that is, do not display .) The non-black and non-white parts are displayed in a transitional manner. Partial transparent output of the background color. The foreign name is "mask" and the Chinese name is "Key-out ".
Mask Tool

To achieve image fusion, three steps are required:
1. Create two layers in an image. Layers 1 and 2.

2. Use the mask on Layer 2. When Layer 2 is selected, click the mask tool on the panel. Effect

3. Use the gradient tool on Layer 2. Set the foreground color to black and the background color to white. On the toolbar, select the gradient tool and pull the image from left to right. Effect

At this time, if we hide Layer 1 (the small eye at the front of Layer 2 in the dot layer Panel), we can see that the layer is displayed in transition. This is the transitional effect of the mask.