8-2 First introduction to masks – Beginner’s tutorial

Before continuing, please make sure you fully understand the knowledge in Chapter #04, that is, the meaning and role of black, white and gray in the channel. Otherwise the following will be difficult to understand. Now imagine that we want to remove the edges of a painting and hang it on the wall. The best way to do this is to use scissors to cut off the unnecessary parts. Cut along the red line as shown in the picture below. It is obvious that this cropping has caused permanent damage to the painting and cannot be restored. This situation is just like the operation we did on the image in Photoshop before, it is a destructive operation. Although the operation can be undone to achieve the purpose of restoration. But we also know that undoing is actually the return of the historical record, and since the operations in the historical record are linear, other operations must be undone even if they are correct. For example, if we crop first and then make color adjustments, then to undo the cropping, we must first undo the color adjustments. Now imagine that we want to remove the edges of a painting and hang…