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Table of Contents

  1. Introduction
  2. Creating a Texture with an Opacity Mask Using Adobe Photoshop
  3. Creating a Texture with an Opacity Mask Using Macromedia Flash (PNG)
  4. Leveraging the 256 Levels of Transparency in Alpha Channels Using Macromedia Fireworks
  5. Creating a Picture with an Alpha Channel Gradient for Display in a Transparent Flash Animation Blending with the HTML Page Background
  6. Creating an Alpha Channel Feather Effect in Photoshop (PSD)
  7. Creating an Alpha Channel Feather Effect in Fireworks (PNG)

Creating Bitmaps with Alpha Channels for Transparent Flash Applications, Director Bitmap Sprites, and Shockwave 3D Overlays

Creating an Alpha Channel Feather Effect in Fireworks

  1. Open a JPEG file in Fireworks.

    A photo with a light spot on a wooden floor

    Figure 36. A photo with a light spot on a wooden floor

  2. Select the Oval Marquee tool in the toolbar.

  3. Select Feather in the Edge pop-up menu in the Property inspector and set the value to 50.

    The Edge pop-up menu set to Feather

    Figure 37. The Edge pop-up menu set to Feather

  4. Select an oval area of the photo to circle the light spot.

    The selected area circling the light spotr

    Figure 38. The selected area circling the light spot

  5. Press Control+X to cut the image.
  6. Press Control+N to create a new file, set the canvas to be transparent, set the canvas size to about 500 pixels by 500 pixels, and click OK.
  7. Press Control+V to paste the clipboard. The new picture only shows the feathered area of the photo.
  8. Select File > Export Preview.
  9. In the Options tab of the Export Preview dialog box, select PNG 32 from the Format pop-up menu and click the Export button.
  10. Give the file a name of your choice and click the Save button.

Where to Go from Here

This article has shown you five techniques to quickly and easily create alpha channel bitmaps.

Leveraging the power of alpha channels, you could use a 3D package such as Maya or 3DS Max to create two prerendered images: one only with colors, the other only with shadows. The one with shadows could be converted to alpha using the Macromedia Fireworks MX 2004 Convert to Alpha filter. This allows you to composite scenes-creating two bitmap sprite channels or two overlays-changing dynamically the alpha channel if need be. You can easily composite two bitmaps using the score in Macromedia Director MX 2004-creating two sprites-one on top of the other. For Shockwave 3D projects, you may create two instances of the Overlay Tweening behavior in the Chrome Lib in order to create two overlays-just drag and drop the same behavior twice, each instance pointing to a different bitmap as a parameter.

Concerning Shockwave 3D, remember to set the texture render format to 32 bits (RGBA8888) for overlays to use the full alpha channel data - Shockwave 3D default render format is 16 bits RGBA5551. To this end, you can use the Texture Render Format behavior in the Chrome Lib. Another tip concerning textures for overlays is to have powers of two width and height, e.g 512 x 512, 256 x 256, 128 x 128, 64 x 64 and so on... this way the textures will be crisp. With the extractAlpha() and setAlpha() Lingo instructions, you can extract the alpha channel from a bitmap cast member and assign it to another. You could create a new bitmap cast member on the fly by compositing the color information of one bitmap with the alpha channel information of another using the Lingo imaging API: new(#bitmap), image(), copyPixels().

As you have seen in this article, Flash is no stranger to alpha channel bitmaps. You can either create a transparent background for a transparent Flash application or use an alpha channel to composite a picture with a vector symbol whose color will be changed using ActionScript.

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