Start photoshop and open a cartoon tree file.
Select the Lasso tool:
Hold down Shift to draw the following selections.
Press Ctrl+Shift+N to create a new layer, execute "Select"-"Modify"-"Smooth", and set the smoothing radius to 4px. Fill the selection with white, the effect is as follows:
Ctrl+D deselects and adds the "Bevel and Emboss" layer style to this layer. The settings are as follows:
The final effect is as follows: