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Discovering Video tools: DoggyFX TV Snow/White Noise

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  - Getting Started - DoggyFX - Time StretchingReducing Flicker - DoggyFX:Transitions -
- DoggyFX:Spritesheets - DoggyFX:Flicker - Alpha masking & TV Snow/White Noise - more DoggyFX -

Another cool set of effects can be found in DoggFXs "Other FX" collection. For example, the White Noise effect creates something that looks like TV snow.

When applying some of these effects filters, you may find an optional checkbox to use the Alpha channel.

Let's take a look at how to create such a selection or mask in the alpha channel.

< click for fullscreen view
In the main Tools panel you can find several tools that can be used to create a selection: Lasso, rectangular, oval or magic wand tools, they all are part of the 'Alpha' tools.  Right-click them for more options. Left cick to activate.
For example, using the Oval (circle) Alpha tool, we can click and drag from about the center of the image to the outisde and create an oval selection. The marching ants show the curent selection.

You can use the Shift key while working with these alpha tools in order to add to the current selection. When drawing the selection with the left button, it will then add to the current selection. When drawing with the right button, it will remove from the current selection.
It is a good idea to occasionally take a snashot of the alpha channel, work in progress, especially if you're creating very complex masks.

Use the menu:

Alpha>Store alpha...

to grab a snapshot.
The Alpha menu aso has a Transform option. This can be used to reposition the mask, or scale and rotate it.

< click for full view

Here we used the Transform Apha to re-center the seection and slightly increase the size.

You may aso want to blur the Alpha a little, so that the selection is not a sudden switch from fully enabled pixel to fully disabled. A gradual ransition is ften preferable.

Alpha>Blur alpha...

Set the amount of blurring.  Click OK.

Two stored alpha images: lower left is showingthe original, with a crisp and sudden transition from black to white. The upper-right version shows a blur effect on the alpha was applied. There is a gradual transtion through greyscale values.

The dashed lines on the marching ants display may not look much different after blurring the alpha. That's because the dashed lines show where the level is at 50%  - between fully selected and fully non-selected. Blurring that doesn't change much about where the 50% level is - it typically is still at the same place. But instead of transitioning there from fully enabled to fully disabled, or from opaque to transarent, or from white to black if seen as a greyscale, you will expect to see a grey gradient around that line. Be sure to Store the alpha again, or click "Get Alpha" in the currently stored view of the earlier alpha image.

The current selection is on the inside of the oval zone. We would like to use the outer part.

Simply Invert the alpha from the Alpha menu, or click 'Invert' on the stored version, followed by 'Replace'.

With the alpha channel now in place and ready to go, use the DoggyFX tool with 'Use Alpha?' selected.

Notice also that in this case you could limit the scope of the effect to some of the frames instead of it affecting the entire clip. By default however, all framesare selected. This clip has 120 frames, so it starts at frame 0 and goes through frame 119.

And here it is.

Below is a version converted to a Flash stream after saving it as an AVI.

next part:

  - Getting Started - DoggyFX - Time StretchingReducing Flicker - DoggyFX:Transitions -
- DoggyFX:Spritesheets - - DoggyFX:Flicker - Alpha masking & TV Snow/White Noise - more DoggyFX -