How can I select the convex hull of an existing selection in Photoshop. In other words, how does one fill the holes in a selection in Photoshop?
Consider a donut shape. You use the wand to create a selection of the donut shape, but the hole of the donut remains unselected. Is there a tool or sequence of actions to fill the "donut holes" in a selection, preserving the precision of the outermost selection lines?
This same question was asked previously, but for Gimp.
You can hold down the Shift key and use any selection tool to add to an existing selection.
You can also hold down the Option/Alt key and use any selection tool to subtract from an existing selection.
You could also switch to Quick Mask Mode and use painting tools to "paint" your selection.
You could also create a Layer Mask of the current selection, then paint on the layer mask.
You could also Save the Selection via
Select > Save Selection, then paint on the alpha channel which is created in the Channels Panel.
The Photoshop help files may be enlightening for general operations such as this.