Masking out hairs using Alpha Channels

Standard

Alpha channels are basically specialized selection processes. Alpha channels are used to make, store or edit selections made using tools such as Lasso, Magic wand or Pen tool.

Alpha channel is another type of image masking. When we say mask, it is an 8-bit channel using 256 levels of Gray, ranging from 0(black) to 255(white). With that being said, alpha channel is a masking technique which defines a selection in black, white, and varying shades of Gray pixels. White acts as the selected pixels; black acts as the unselected area and the levels of Gray define what is partially unselected or selected depending on your view point.

Here you will learn how to mask out hairs or in this case fur using the Alpha channel technique. Let’s begin:

1. Open the image of your choice, select the pen tool and make a clipping path on the part of the image you want to edit. If you’ve noticed, I have two images with the labels �1� and �2�. This represents the two clipping paths I�ve made for this image. For the image with the label �1�, I did a clipping path on the inner part of the hood. (Notice the faint clipping path line). For the image with the label �2�, I made a clipping path on the outer part of the hood. (The clipping path is more obvious in this image)

alpha channel

2. After you’re done with the clipping path, click on the channel palate. From there, you’ll see the RGB, red, green and blue channels. Look for and duplicate the channel that has the most contrast. For this picture, I will duplicate the blue channel.

alpha channel

3. Go to the paths palate and select �path 1�. Right click �path 1� and click the category �fill path�.

alpha channel

4. Once you clicked on �Fill Path�, another menu appears. This time, select and use the background color. Notice how the path is filled with black after you selected the use with background.

alpha channel

5. Now select the brush tool, brush the upper portion of the hood that wasn’t included in the path so that it would look smooth and natural.

alpha channel

6. Press ctrl and click on �path 2� to activate. On the upper menu bar, click on the �Select� option and then click on �Inverse�. You can also use the shortcut Ctrl+Shift+I to invert the path selection.

alpha channel

7. Once you have the inverse the selection, press Alt+Delete to turn the foreground color to plain white. Again, choose the brush tool and continue brushing the portion of the foreground that isn�t transformed to white.

alpha channel

8. When you�re done, go back to the channel menu. Choose the duplicated blue copy you’ve done earlier and at the lower portion select the �load channel� option to activate.

alpha channel

9. After activating the channel, go to layers and add an empty layer (a transparent layer will come out named �layer 1�). Now add a layer mask and select the transparent layer to start changing your background. You can opt to use a plain color for the background; I used the color yellow green in this tutorial.

alpha channel
alpha channel

10. But if you don’t like simple colours for your background, you can also opt to add a more dynamic design. Here, I’ve decided to put an interesting vector designed background to make the picture more attractive.

alpha channel

11. Done! You have now completely masked out the old background and replaced it with a more creative one.
source
alpha channel

code : http://www.tutorialkit.com/tutorials/Alpha-Channel-Tutorial-97566.html

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