Masking An Image In Photoshop

Let’s say you have a great shot you want to use on your website but you want to change the backdrop. You need to remove the areas of the image that you do not want. To do this we use a layer mask. A mask is a black and white layer which determines what parts of the layer are shown and which are hid. By simply changing areas on the mask from white to back will remove parts of the image.

I’m going to give an example of how to use the masking tool which is covered on our Photoshop CS 4 Level 2 Course, so basic Photoshop knowledge is required for this exercise. If your interested in photoshop training courses check out what Systematix can offer you.

Adding a Mask to a Layer

To add a mask to a layer, simply select the layer and then hit the “Add Layer Mask” button at the bottom of the layers dialog. This will then create the mask which will sit to the right of the layer preview.

Add a background

At this point I’m going to create another layer to serve as a temporary background to aid the masking process. In this case I’m choosing to use a green background as it will contrast well with the colours on the image. It should help in determining the mask's accuracy. So I create a new layer behind my original layer and fill it with green.

Range Mask the Image

You can mask an image in many ways but in this example the image I am using has a solid background that makes it easy for us to do as we can use Photoshop’s Colour Range tool.

To do this I select the mask on my image layer. Then open the Colour Range tool which is found under Selection -> Colour Range.

Inside the range match tool I firstly click on the white background to sample the colour I want to match. Then I select invert to tell the tool that I want remove the matched area. I then adjust the fuzziness until I feel that the tool has taken care of any intricate details in this case her hair. I do not worry about it removing some of the image as I can repair this more easily than I can the intricate areas.

Touch Up

Once I have removed most of the background I have to do some touching up as I’ve removed slightly too much of the white in the image. Now using the colours black and white I can add and remove areas from the mask. I use the brush tool (Shortcut: B) and white to restore the areas that were affected by the mask. I also use the brush with black to tidy up any rough edges.

Finalizing

Once you have touched up your mask all you can then add your desired background and scale your image to your liking.