Duotone - The Basics
  Duotone - Advanced
  Direct from RGB
    - HSL
    - Colour Balance
    - Selective Color
    - Color Hue & Tone
  Using Masks
 8. Using Masks with Colour Alteration Tools

Using Masks

Masks provide an excellent way to isolate portions of an image. Once isolated, the mask is used either to direct an alteration to a specific area, or to protect the area from an otherwise global alteration.

The use of masks in combination with many of the tools we have been discussing here brings real power to your graphics armory. Photo-Paint has some of the best masking tools in the business - but that is another story entirely. For the current exercise we will use a fairly simple mask to isolate a portion of an image and then apply colour changes either within or outside the mask. The methods described here are commonly used to create grayscale images containing specific, brightly coloured objects, to name but just one possible use. In reality, once you set masks in motion (especially when combined with layers) there are almost unlimited possibilities for creative expression in digital imagery. But of course, you know all this already, so lets get started !


"Let's Go Surfin' Now
Everybody's Surfin' Now..."

For this final exercise I have selected an image from Draw 8 disk 3, image 834001.wi in the Photos/Active folder.

This image was resampled to a width of 600 pixels and sharpened slightly with the Unsharp Mask.

If you need a copy of the resampled, slightly sharpened image you can get it HERE or click on the picture.



Making the Mask

I created a mask around the yellow surf board using the following tools in this order:

  1. The Lasso Mask tool around the basic shape.
  2. The Magic Wand Mask tool with a tolerance of 8 in subtractive mode at high magnification to remove extra areas outside the board.
  3. The Mask Brush Tool in both additive and subtractive modes at high magnification to clean up the edges.
  4. The Mask > Shape > Smooth command, radius = 4 to smooth the edges.
  5. And finally the Mask > Shape > Feather command, direction = Average, distance = 4.

If you don't wish to recreate it, you can download it HERE
(or click on the mask image to the left).
But then you will miss out on all the fun of creating it !

To use the supplied mask you must first load it.

   - Mask > Load from Disk     to load it into your image.

Once the mask is loaded create a checkpoint so that you can return to this stage.

Your image should look like this one:

If you cannot see the mask marquee then you will need to make it visible

   - Mask > Marquee Visible

The mask can be used as is to focus changes TO the yellow board. Or it can be inverted to protect the board FROM changes.

The mask can also be used on a copy of the original image object or even on another object if it has a similar shape.


Desaturated Background

Lets try some simple colour alterations using some of the tools we used earlier.

Here I want to change the background to grayscale (desaturate) and leave the surfboard in full colour. In order to operate on a section of the image other than the surfboard, we need to INVERT the current mask.

   - Mask > Invert or click the Invert Mask icon on the Tool bar


Now remove all the colour from the inverted mask area

   - Image > Adjust > Desaturate.

Now everything except the yellow surfboard appears to be in grayscale.


Paint it Red!

Lets take it a bit further. Lets Paint it Red !

    - Edit > Undo Special > Restore to Checkpoint (PP8) or
      Edit > Restore to Checkpoint (PP9).

    - Repeat the steps above:
      invert the mask, then
      desaturate the background.

    - Image > Adjust > Color Balance
      use the following settings:
      CR100, MG-60, YB-80, S M L
      (using the same codes as before).

Your image should look like the red one above.


Paint it Sepia !

Alternatively you can create an old sepia looking image using the following settings in the Colour Balance Dialogue:

CR40, MG0, YB-70, M H


Blue Hawaii at the Moulin Rouge

To make the surf board really stand out all we need to do is to invert the mask again and apply additional colour adjustments to the board itself.

    - Restore to the checkpoint again if you need to and
    - Recreate the red backgrounded image (see above), then invert the mask:
Mask > Invert

If you cannot see which is selected or not, turn ON the Mask Marquee

   - Mask > Marquee Visible (or click the Mask Marquee Visible icon on the Tool bar)

Now transform the image simply by inverting the colours within the masked surf board region:

   - Image > Transform > Invert.

Now the surf board will appear blue as shown here


Adding Effects

Using masks and colour transformations plus other effects lets you create some quite stunning images.

Try to recreate some of these (hints are provided):

(zoom blur then colour balance)
(impressionist, solarise, swirl then vignette)


(sorry, no hints on this last one)


Almost finished - just the concluding remarks to go.


Copyright ©, 1999. David Mutch Ph.D. and Visionary Voyager Corporation.
All rights reserved.