How does the mobile phone change the photo background to black?

The phone can change the photo background to black, as shown below:

1. First import the material photos into snapseed, and then select the Text tool.

2. Enter a space when prompted, and then click OK.

3. Click the water drop icon below and click "Inverted". Then click the palette icon and select black. Click the check mark to confirm.

4. Click the icon with an arrow in the upper right corner, click "View Modification", click "Text" in the lower right corner, and click the pop-up brush icon.

5. Click OK after the effect is satisfactory, and return to the main interface to save or export.