Academic Technology Center
Learning with Technology Collaboratory

Tutorial: Combining Images

(Continuation from the "Cutting Out an Image" Tutorial)Finished Image

When we combine several images together, it is common to run into problems of scale, position, and rotation. In this tutorial, we are going to continue creating the image to the right. In the first section of the tutorial, we cropped and straightened the background and selected the sailor using these files: Meredith.jpg  sailor.jpg

So far, we cut out a Sailor from an image

If you went on to the advanced step, your sailor has a layer mask applied, but it still needs to be moved over to the background image. Even if you did not use a layer mask for this project, it's very important to know how to move layers between documents.

To move layers between documents

The easiest way to move layers from one document into another is to saparate the documents from the tabbed interface:

Click and drag the tab corresponding to the document you want to copy from. Pull the tab away from the top of the window, and it will separate into its own document window

Why is there a locked background layer?

Some image formats, like jpg, do not store transparency information.When you open one of these formats in Photoshop, the background layer is locked, preventing you from adding tranparency information. We convert the background layer into a regular layer so that we can hide portions of the layer.

Unlocking a layer

Finally, we can add a Layer Mask

With the sailor selected, you can open the Layer menu and select Layer Mask > Reveal Selection. This will create a mask that hides everything on the layer except the sailor that you selected.

There is a quick shortcut to add a layer mask, too. Instead of using the Layer menu, you can simply click the "Add Layer Mask" button at the bottom of the Layers panel.

Two ways of adding a Layer mask (Click to expand)

Both methods, side by side


How Layer Masks work: A side note

Before continuing, let's take a moment to discuss how a layer mask works. It is important to understand why the technique above produces a cut-out of your image.

A layer mask is a greyscale image that affects the visibility of the layer that it is attached to. When a layer mask is black, the contents of its layer are hidden. When a mask is white, the contents are completely visible. Shades of grey make the contents partially transparent. Compare the ordinary document below with the two layer mask examples to see how layer masks can affect layers.

Ordinary Layers
An ordinary document, with no layer masks added.

Example: a circular cutout mask (Click to expand)

Layer Mask Added
Layer mask with a black circle added--a portion of the top layer is hidden.

Example: a gradient mask (Click to expand)

Layer Mask with a gradient
Layer mask with a gradient added--the layer's visibility varies as the gradient changes.

Masks provide a very flexible and non-destructive way to modify the appearance of a layer. Most of the drawing tools, filters, and image adjustment features provided by Photoshop can be used with layer masks, so as you learn more advanced editing techniques, this feature will become increasingly useful.


Take a look at the mask you've just created

Now we know that in the world of layer masks, Black means "show" and White means "hide." When you create a selection and add a layer mask, Photoshop automatically creates a black and white image based on the selection. At this point, you can adjust the borders of your mask using the Masks Panel (new in CS4) or by using painting tools and image filters. This method is much more flexible than copy and paste because you can add to or subtract from your mask at any time as you create your final image.

This section is complete!

Maintained by
Last modified: May 04, 2007, 08:28 EDT
[WPI] [ATC] [Back] [Top]