Painting a transparency?

Hi,

I have Photoshop, but am a bit of a novice, so go easy on me

I have loaded a 24bit/pixel tga graphic into photoshop, and I want to paint a transparency hole in the middle. Not a pure circle, a sort of ragged hole, which I would like to do with a Brush tool. However, the colour I want to paint the hole with should be rendered as transparent when the tga is saved out again.

Can some kind soul give me a step-by-step for this, as I find the manual somewhat less than user friendly.

TIA

Vi

Here's where I learned to do it:

http://www.robinwood.com/Catalog/Technical/SL-Tuts/SLTutSet.html

Many thanks for that Amity. I have struggled with that tutorial before, and all other tutorials I have looked at all assume that you are starting with a blank canvass. In my case I am starting with an existing graphic, and I wish to paint a transparent splodge in the middle of it.

I just cannot find how to do this (too much wood, hiding my tree I think)

Any clues?

Vi

I'm not sure of the problem you're having. If I understand it, this is the way I would do it (which may not be the best way to do it; I'm not a Photoshop expert.

Create a new layer on top of your graphic. Fill it with complete white.

Take whatever brush you're making to make the "splodge." Do a black splodge. You can adjust the transparency of the layer to see that you have your splodge in the right place; put the layer back to fully opaque when you're sure you have it.

Select this entire layer; copy the layer.

Switch your channels. You have the standard four. Create a new channel to be your alpha channel.

After you have created your new channel, select it. Now paste from the layer with your splodge.

Switch back to your layers, and hide your splodge layer.

Now save as a tga. Be sure to select the option to save alpha channel. It has to be 32-bit.

You should have it then.

Many thanks for that Amity.

I will get to work on that right away.

Vi )

Amity, I'm wondering why you'd bother with an extra layer. Why not simply paint directly on the alpha channel itself?

Vi, here's how I'd do it. This should take you all of about five seconds:

1. On the Channels palette, click the Create New Channel button at the bottom. A new channel will appear, which by default it will be called Alpha 1 (not that the name matters in any way). This is your alpha channel, the transparency map for the image.

You'll notice that the canvas will have turned black. This is because when you created the alpha channel, visibility on the color channels was automatically switched off. Don't worry; all the color information is still there. It's just temporarily hidden, so that you can see the alpha channel. You can turn visibility on or off for any and all channels at any time, harmlessly, simply by clicking the little eyeball box to the left of each channel's name.

2. On the alpha channel, flood the canvas with white, and then paint your black splotch in the middle. If you need to see the color channels in order to know where to paint the splotch, simply turn their visibility back on. Just make sure the alpha channel is the only one active (name highlighted in the palette), so that you don't paint on the color channels. Remember, we're painting transparency here, not color.

Note, when the color channels are visible, the alpha channel will display as an overlay. Opaque areas of the image (white areas of the alpha channel) will show as normal. Transparent areas (black on the alpha channel) will show as reddened. When the color channels are not visible, the alpha channel will display simply as a grayscale map (because that's what every channel actually is).

3. Save your image as 32-bit TGA, and upload to SL.

Chosen is always right. however, I have a STEP 0 to add.

Step 0. Learn what channels are, and how they are different from layers.

There are many other posts (most by Chosen Few) that explain the difference better than I can, so I will send you to search for one of those.

Many thanks.

Both methods worked perfectly, and I am a little wiser now.

The second method used fewer steps, but I think I can see a use for copying from a layer to the alpha channel, so two great replies.

Thanks again,

Vi )