The Art of Masking
Michael Cervantes Michael Cervantes is a Corel® C-Tech volunteer, CorelDRAW® Certified Expert, and Certified Instructor. He graduated from the Southern Institute of Business and Technology in Dallas, Texas. In addition to being a desktop publisher, Michael has been a freelance graphic artist since 1989. He has published several articles about CorelDRAW and Corel PHOTO-PAINT®, and he routinely helps Corel users in the Corel newsgroups. Michael was a contributing author to CorelDRAW 10: The Official Guide and other publications.
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CorelDRAW X4 — Insights from the Experts
The art of masking Corel PHOTO-PAINT is an extraordinary bitmap-editing application that features many tools for masking digital images according to user convenience and needs. Some of these tools are based on techniques used traditionally in printing, photography, and painting, while others have come from the imaginations of software engineers. These versatile masking tools offer the skilled user many masking techniques, some of which are so creative that their use constitutes a form of art. The most important and efficient Corel PHOTO-PAINT masking technique is the clip mask. What is a clip mask, and how does it work? Imagine a transparent piece of paper placed over a photograph. You can paint over this paper with a magic ink that adds transparency to the underlying photograph or subtracts transparency from it. The advantage of this method is that the ink does not dry until you are satisfied with your work, and only then do the changes become permanent. The original image is kept intact, because you are not painting directly over the photograph. Why is this so fantastic? First, the technique is nondestructive; second, you can use almost all Corel PHOTO-PAINT tools and effects while working on the mask; third, changes are displayed immediately; and fourth, you can apply or discard the clip mask whenever you want. The clip mask is associated with an object, which is why you should convert the background to an object if you want to use a clip mask on it. Converting the background to an object is not a problem, because you can combine any object or layer with the background whenever necessary, even if the background is clip-masked. In addition to providing useful tips about working with clip masks, this tutorial also gives you some general tips about masking. You will learn some techniques that will help you increase your productivity and improve the quality of your masks. Learning these methods is the first step in improving your masking technique.
Example 1: Use masking to create transparent edges You need to create soft transparent edges on three sides of an image, because the image will be used on the interior left-hand page of a magazine.
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Open the sample image in Corel PHOTO-PAINT (locate the file strawberries.tif in the folder Program Files\Corel\CorelDRAW Graphics Suite X4\Tutorial files). If necessary, choose To fit from the zoom level list box on the property bar. CorelDRAW X4 — The art of masking
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Open the Objects docker (press Ctrl + F7, or from the menu bar, click Window Dockers Objects).
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Convert the background to an object. To do this, click the Create an object from the background button at the bottom of the Objects docker, or from the menu bar, click Object Create From background.
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Double-click the Rectangle mask tool in the toolbox to create a mask around the image.
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Click Mask Mask outline Reduce, and set Width to 50 pixels. This setting evenly reduces the size of the mask 50 pixels from the border. This approach is faster, and more precise, than drawing the mask and aligning it with the center of the image.
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Right-click the object thumbnail in the Objects docker, and select Create clip mask From mask, or from the menu bar, click Object Clip mask Create From mask. A clip mask icon is created to the right of the object thumbnail in the Objects docker. The clip mask represents the special transparent sheet of paper mentioned previously. Notice the red outline around the clip mask icon in the Objects docker (Figure 1), which tells you that the clip mask is active. You can click the object thumbnail to deactivate the clip mask and work directly on the image, or you can click the clip mask icon to reactivate it.
Figure 1: The red outline shows that the clip mask is active.
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Now a magic moment: Open the Gaussian blur dialog box (from the menu bar, click Effects Blur Gaussian blur), and play with the Radius slider until the image borders appear with a soft transition from solid to transparent.
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We want to return the right side of the image to normal (hard edge) while keeping a soft border for the other three sides. To do this, activate the Paint tool (press the P key, or click the Paint tool in the toolbox), and select Airbrush from the Paint tool picker on the property bar. Click the Open advanced options button on the property bar to expand the advanced options, and set brush Transparency to 95. Set Foreground color to white (click the White swatch on the color palette), and paint on the right side of the image. The edges are now complete (Figure 2).
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CorelDRAW X4 — Insights from the Experts
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To make the changes permanent, combine the clip mask with the object (right-click the clip mask icon in the Objects docker, and select Combine clip mask, or from the menu bar, click Object Clip mask Combine).
Figure 2: Transparent edges are created on three sides.
Example 2: Use masking to change image luminosity The clip mask is useful not only for masking transparencies, but also for masking color and correcting luminosity. Frequently, you find images that are highly contrasted or that have shadows that cover large areas of the image. By using image luminosity to mask these types of images, you can bring out image detail. The process is simple: you invert the image luminosity, so that what is white changes to black, and what is black changes to white. The black area of the mask protects the highlights, and the white area exposes the shadows to changes and gradually exposes the rest of the image. Study the following example to see how this works.
CorelDRAW X4 — The art of masking
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A travel agency is promoting a destination. You have been assigned to enhance the shadows in this photograph to expose important details (Figure 3).
Figure 3: The photograph contains shadows that need to be adjusted without affecting the highlights in the image.
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Open the sample image with Corel PHOTO-PAINT (locate the file seaside_village_shadows.tif in the folder Program Files\Corel\CorelDRAW Graphics Suite X4\Tutorial files). If necessary, choose To fit from the zoom level list box on the property bar.
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Duplicate the image (click Image Duplicate).
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Convert the duplicate to Lab Color mode by clicking Image Convert to Lab color (24 bit).
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Press Alt + 1 to open the Channels docker and activate the Lightness channel (or from the menu bar, click Window Dockers Channels, and then click Lightness channel).
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Copy the Lightness channel to the Clipboard (press Ctrl + C, or from the menu bar, click Edit Copy).
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CorelDRAW X4 — Insights from the Experts
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Activate the original image (click Window seaside_village_shadows.tif).
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Duplicate the background object by pressing Ctrl + D or clicking Object Duplicate from the menu bar. (You can also right-click the Background object in the Objects docker and choose Duplicate selected.)
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Rename the new object. To do this, right-click the object in the Objects docker, and choose Properties . In the Object properties dialog box, type “Enhanced” in the Name field, and click OK.
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Activate Paint on mask mode (press Ctrl + K, or from the menu bar, click Mask Paint on mask).
10 Paste the Lightness channel from the Clipboard into the Paint on mask image (click Edit Paste Paste as new selection). 11 Invert the mask by clicking Image Transform Invert. Note that the highlights are now black and that the shadows are white (Figure 4).
Figure 4: The highlights and shadows have been inverted.
12 Deactivate Paint on mask mode (press Ctrl + K, or from the menu bar, click Mask Paint on mask). 13 Create a clip mask on the “Enhanced” object by right-clicking the “Enhanced” thumbnail in the Objects docker and choosing Create clip mask From mask. Note: You can also invert a mask by right-clicking the thumbnail and choosing Create clip mask From inverted mask.
CorelDRAW X4 — The art of masking
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14 Activate the “Enhanced” object, and deactivate the clip mask, by clicking the “Enhanced” object thumbnail in the Objects docker. 15 Open the Tone curve dialog box (press Ctrl + T, or from the menu bar, click Adjust Tone curve). Adjust the curve to enhance the shadows and reveal detail. You should observe how the shadows become lighter while the highlights remain unchanged, and how the other tones change gradually. 16 To see the changes to the “Enhanced” object, hide the background object by clicking the background eye icon in the Objects docker (Figure 5).
Figure 5: The highlights are enhanced.
Example 3: Use channel masks to replace the image background The perfect result of using this efficient, magical technique depends on how fast and how precisely the initial mask is created. Corel PHOTO-PAINT beginners tend to activate the Magic wand mask tool too often, and intermediate users do the same to the Path tool, but you should remember that masks are 8-bit channels. More often than not, the mask you are looking for can be found inside a channel, especially complex masks that would be difficult and tedious to create with conventional mask tools. If you want to mask like a pro — fast and easy — take a good look at the following example.
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CorelDRAW X4 — Insights from the Experts
The sky in the image below is flat and pale (Figure 6). You want to enrich this beautiful composition by using a different sky and adjusting the sea color slightly.
Figure 6: The sky in this photograph lacks color and contrast.
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Open the sample image with Corel PHOTO-PAINT (locate the file seaside_village_detail.tif in the folder Program Files\Corel\CorelDRAW Graphics Suite X4\Tutorial files). If necessary, choose To fit from the zoom level list box on the property bar.
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The main color you want in the sky is cyan, and the unwanted color is yellow. If you want to mask the sky, the channel to look at is the yellow channel. Press Alt + 3 to activate the yellow channel, or click Yellow channel in the Channels docker. This channel shows an almost perfect mask for the sky (Figure 7).
CorelDRAW X4 — The art of masking
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Figure 7: The sky has been isolated in the yellow channel.
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Copy the yellow channel to the Clipboard (press Ctrl + C, or from the menu bar, click Edit Copy).
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Select the composite channel (press Alt + 0, or click the CMYK channel in the Channels docker).
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Activate Paint on mask mode by pressing Ctrl + K or clicking Mask Paint on mask from the menu bar.
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Click Edit Paste Paste as new selection to paste the mask from the Clipboard.
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Deactivate Paint on mask mode (press Ctrl + K, or from the menu bar, click Mask Paint on mask).
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Import a photo of a sky that you want to use for the background. To do this, press Ctrl + I, or from the menu bar, click File Import. Locate the file sky.tif in the folder Program Files\Corel\CorelDRAW Graphics Suite X4\Tutorial files. Drag the sky object, as necessary, so that it covers the original sky area.
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Create a clip mask in the new sky object by using the current mask (right-click the sky object thumbnail in the Objects docker, and choose Create clip mask From mask). You can also create the clip mask by clicking Object Clip mask Create From mask from the menu bar.
10 The main problem with the original sky was the lack of cyan. Change the merge mode of the sky object to cyan (right-click the thumbnail of the sky object in the Objects docker, click Properties, select Cyan from the Merge list box, and click OK).
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CorelDRAW X4 — Insights from the Experts
11 The new sky is darker than the original image. To reduce the object’s opacity, right-click the object in the Objects docker, click Properties, and move the Opacity slider until the sky illumination looks natural compared with the original image. 12 The new sky color is covering part of the original houses, so we want to increase the clip mask contrast. Select the clip mask by clicking the clip mask icon in the Objects docker, and open the tone curve ( Adjust Tone curve). Drag to adjust the tone curve until you are satisfied with the result (Figure 8).
Figure 8: Use the tone curve to increase contrast.
13 Open the Info docker by clicking Window Dockers Info. Move the cursor over the sky area while reading the color values in the Info docker. The values show that the sky has almost no magenta. To add magenta, duplicate the sky object (right-click the object’s name in the Objects docker, and choose Duplicate selected), and then change the merge mode of the duplicate object to magenta (right-click the thumbnail of the object in the Objects docker, click Properties , and select Magenta from the Merge list box). Decrease the object’s opacity, and click OK. 14 The sea area also needs enhancement. Activate the object that has cyan as the merge mode, and duplicate it (right-click the object’s name in the Objects docker, and choose Duplicate selected). 15 Discard the clip mask from the new object by right-clicking the clip mask icon and selecting Remove clip mask. Move the object down to cover the sea, and change the object's opacity to approximately 10%. 16 Create a clip mask to hide the object. To do this, right-click the original sky object thumbnail in the Objects docker, and choose Create clip mask To hide all. 17 Activate the Paint tool (press P), click the white color swatch on the color palette, and brush over the sea to let the cyan come up through the clip mask.
CorelDRAW X4 — The art of masking
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18 Combine all objects with the background (click Object Combine Combine all objects with background), and save the file. The image is now finished (Figure 9).
Figure 9: The sky has been replaced to enhance the photograph.
When used properly, Corel PHOTO-PAINT is a friendly and capable tool. Remember: when a mask is needed, the first step is not necessarily to activate a masking tool, but to take a good look at the channels.
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CorelDRAW X4 — Insights from the Experts
