Image layers, used in image editors, work like transparent paper. The layers allow you to draw on top of the image beneath them without actually altering the image itself. But once you add lines or shapes to a layer, you'll want to secure the layer. Locking a layer maintains the opacity of the objects on it, which safeguards the visibility of the layers from any effects you may add later on. If you use Paint Tools SAI to handle your image editing project, you can secure your layers with the image editor's lock feature.
Launch Paint Tools SAI. Select the "Open" option from SAI's "File" heading to load an existing project or a new image into the program.
Click on the layer you'd like to lock in the SAI's layers window. The unlabeled "Layers" window is located in the bottom left corner of the program.
Drag the "Opacity" slider to the left or right to set your layer's transparency level before locking it.
Click inside of the "Preserve Opacity" check box to lock the selected layer's opacity. The word "Lock" will appear on top of the layer. To unlock the layer, reselect it. Clear the check from the "Preserve Opacity" check box.
Select the "Save" option from SAI's "File" heading to preserve your changes.
If you're starting a new project, select the "New Layer" option from the "Layers" heading to add a new layer to your image. To work with a project that has multiple layers, simply click on the desired layer in SAI's "Layers" window.