changing existing jpgs?

Hey all,
I am using Photoshop CS2 9.0.2. I know how to make Tattoo's.. Finally I think I got it. But what I am having trouble doing is taking a jpeg that has a black image on a white background and making the white background invisible but keeping the black the way it is. Then using the black as a tattoo. Is it possible to do this? Everything I have tried has failed. Anyone got a nice tutorial on how to pretty much unglue the black from the white background? Any help you can give would be appreciated.

If your tattoo image is truely black and white, all you need to do is make a copy on another layer, invert the image, copy and paste that image to a new channel and use that alpha channel to redefine the black area on a third transparent layer. If you are satisfied with the results then delete the other 2 layers. Keep the third layer and the alpha channel.

One other thing to keep in mind. JPEGs have artifacting in them. You may want to open your info window and move the cursor through the background to see if your white is truely white. If not you may need to clean it up a bit.

What if it isn't a true black and white? like has some various tints of gray? would I invert and erase those?

I usually use my majic wand tool. Just target the white or black area cut or copy and paste into a new layer. Make sure you use transparent as the background. Hide all the layers you don't need . Control click the layer that has your image on it. This will highlight only the tatoo. Make your alpha channel from that. Save as a 32 bit tga and you should be set. Oh you may know this but make sure your image in no larger than 512 x 512. Or it will NEVER rez.

If you want to make all the white of a b/w or greyscale layer transparent, and all the black opaque, use the Multiply blending mode. (Pull down menu in the upper-left of the Layers pallate, shows Normal by default.)

This is essentially how textures on prims are blended in SL... Any white in a texture takes on the underlying color, black is unaffected, and shades in between darken the underlying color proportionately.

Use the Screen mode if you want the opposite: opaque white and transparent black.

Hi Bigdaddy!

As a matter of fact, I did write a tutorial explaining just how to do this some time ago.

You can find it here.

This method doesn't use selections or Blending Modes, and will give you a clean, antialiased edge on transparency, which you can use to make your Alpha Channel. (It will also give you partial transparency where the original image was gray.)

I think it's just what you're looking for.

Hope this helps!