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Painting on Alpha

intro -  part 1 - part 2

PD Particles Tutorials

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Painting on alpha is a technique used at times to create fancy selection masks, through which you can thereafter do additional painting, without impacting the neighboring pixels (those that were not selected).

There are various tools and techniques available for making good selections. The Magic wand, the lasso tool, rectangle and oval tools into alpha, and more. You can often combine multiple iterations or invocations of these tools, with the Shift key to 'add' to the prior selection. Using the left mouse button with Shift will general add to the selection, while using the right button with let you remove from the selections.

Sometimes, it's best to just paint the selection right on there. Perhaps you made a rough initial selection with a rectangle tool, and want to splatter some rough edges along its edges. Perhaps the magic wand is able to pick up some but not all intended regions. PErhaps a color keying approach picked up or left out similar colors inside or outside the desired region. For this and many similar scenarios, you may need the ability to paint on alpha. Even more, you may want to be able to take the existing image and transfer it into the alpha channel.

In PD Pro, there's an option to copy the image from the Swap buffer to the alpha buffer. So if you first copy the image from the Main buffer to the Swap buffer, you're ready to do this.

In PD Particles 1, there is no swap buffer. However, there still is a way to transfer the image buffer's content to the Alpha channel.

This tutorial shows how to do this in PD Particles, and of course the same can be done in PD Pro.

PD Pro Alpha-skills  Tutorials

next:  Storing the alpha channel