Alpha Channel Window

Use

The Alpha Channel window is used to manipulate the alpha and RGB channels of the current 2D image.

For example, you can remove the alpha or RGB channels from the images. SAP 3D Visual Enterprise Author uses the alpha channel of images as an opacity map by default. However, in some cases you may not want this to happen. For example, some model formats use the alpha channel of textures for things like shininess, yet SAP 3D Visual Enterprise Author will try to use it for opacity. In these cases, you can remove the alpha channel completely, or extract it so that it may be saved as a separate image. Also, some images may use alpha channel for transparency rather than opacity, so those images may be opaque in places where they should be transparent and vice versa. The Alpha Channel window can be used to correct these images for use in SAP 3D Visual Enterprise Author.

Features

Fields and Checkboxes	Functional Description
Remove	Removes the alpha channel leaving only the RGB channels. This option is only available if there is an alpha channel present.
Extract	Removes the RGB channels leaving only the alpha channel using one of two methods. This option is only available if there is an alpha channel present. Clear Color Channels: Fills the color channels with solid white. Remove Color Channels: Removes the color channels entirely. This leaves an 8-bit grayscale image.
Replace/Add	Replaces the existing contents of the channel if one is present, or adds a new alpha channel to the image if one is not present. Source: Used to select the base value for the alpha channel. For example, if the red channel is selected as the source, the resulting alpha channel has a high value in areas where the red value is high, and low values where the red value is low. Constant Value: Applies a value of 1.0 to all pixels. Existing Alpha: Uses the existing alpha values for the alpha channel. In combination with the Multiplier option, this allows you to tone down or invert an existing alpha channel. Note that this option functions in the same manner as the Constant Value option. Luminance: Bases the alpha channel on the luminance (the perceived brightness) of the RGB channels. Red/Green/Blue Channel: Applies a red/green/blue alpha value to each pixel. Red and Green: Applies an alpha value from the average of the red and green channels to each pixel. Red and Blue: Applies an alpha value from the average of the red and blue channels to each pixel. Green and Blue: Applies an alpha value from the average of the green and blue channels to each pixel. Red, Green, Blue: Applies an alpha value from the average of the red, green, and blue channels to each pixel.
Multiplier	Multiplies the source value by this value, allowing you to tone down the final values. This value can be negative, in which case the final alpha channel is inverted (high source values become low values and vice versa).
Whole Image	Applies the source value evenly over the entire image
By Key Color	Applies the source value over the parts of the image where the RGB color matches the key color. Unmatched parts of the image have an alpha value of 0 (or 1 if the multiplier is negative) applied. Key Color: Used to select the key color. Tolerance: Determines how similar the current color must be to the key color, to be considered a match. Soft Edges: Considers pixels of any color, except the key color, as a match. Any pixel in which the color is considered a match, but is not the exact same color as the key color, has an alpha value somewhere between the source value and 0 (or 1 if the multiplier is negative) applied. The exact value is determined by how close the match is. Note that this option is only available if the Tolerance value is greater than 0.

Activities

Opening the Alpha Channel Window

Open a 2D image and do one of the following:

Choose Actions 2D Tools Alpha Channel from the Menu bar.
Right-click the image and then choose 2D Tools Alpha Channel.

Removing the Alpha Channel from an Image

Open the 2D image from which you want to remove the alpha channel, open the Alpha Channel window, choose Remove and then OK.

Extracting the Alpha Channel from an Image

Open the 2D image from which you want to extract the alpha channel, in the Alpha Channel window choose Extract and do one of the following:

Choose Clear Color Channels to fill the color channels with solid white.
Choose Remove Color Channels to remove the color channels entirely. Choose OK.

Replacing or Adding an Alpha Channel in an Image

Open the 2D image in which you want to replace or add an alpha channel. Open the Alpha Channel window and do one of the following:
- Choose Replace if the image has an alpha channel.
- Choose Add if the image does not have an alpha channel.
Select the source to use as the channel’s base value.
Select the value with which to multiply the source value and do one of the following:
- Choose Whole Image to apply the source value evenly over the entire image
- Choose By Key Color to apply the source value over the parts of the image where the RGB color matches the key color.
If you selected By Key Color, select a key color and a color tolerance level, and then select the Soft Edges check box if you want to consider pixels of any color except the key color as a match.