How does PS button the picture with black background?

Cutout method of clear outline of black background object

Example diagram:

Open the file, copy the layer, and select the background with the magic wand tool.

2. Menu bar, select/deselect (ctrl+shift+i).

3. Menu bar, select/modify/reduce (1 pixel).

4. Copy the selection to the layer, (ctrl+j), and hide the layer under the main body for viewing.

5. Fill a color, move it under the main layer and check the final effect.

The method of unclear outline of black background object

Example diagram:

Insert the material into the background file and change the material layer blending mode to color filter.