Convert to Alpha

[Blue Ten]

I have a question about converting black and white images (line art) to alpha -- i.e. black-to-transparent images.

I have used Fireworks before and it had a very useful filter under "Other" called "Convert to Alpha". I would use this whenever I wanted to work with my scanned drawings. Hehe, sadly, I don't have Fireworks anymore (was not mine), just CS3 Design Premium.

Anyway, I was wondering if there was a way to achieve a similar result in Photoshop CS3 -- APART from adjusting the blending mode of the line art layer to "Multiply". What I want is the ability to lock out transparent pixels and colorize the line art itself; Multiply is just cosmetic and won't allow this. It would be great if there was some process for this conversion in Photoshop... I'd just make an Action out of it and use it each time :P.

Failing that, is there a program out there that specializes in converting grayscale images to alpha, preferably one that saves them as PNGs or PSDs? I've searched, but haven't been able to find one yet...

This forum has always been a big help to me. Thanks in advance .

[Inactive]

i'm not sure this is what you want to do, but you can copy and paste the line art image into a mask layer created on a image you want to hide out.
open the line art image and select all then copy.
open the image you want to hide (cannot be background layer).
create mask layer ('add vector mask' button on bottom of layer panel)
press left ALT and left click on the newly created mask layer - this will isolate all other layers and present you with the mask layer to modify.
then paste the copied line art image onto this layer. anything that is black will be hidden and white will be visible.
then ALT - left click on the mask image to resume normally and voila.

the image will now be hidden by the black and white pixels on the mask layer. i might not have explained this very well... there are others here who know more than i and they might have a go if i am wrong.

[scunny]

Click Select-Colour range...
use the eyedropper to select white area on your image, leave fuzziness set @ 100
Click OK
Hit Del to erase white area of your image (make sure layer is not locked)

OR if you want to create an actual alpha channel...

Select colour range as above, then...
Click WIndow-Channels
A box should appear
Click new channel (at bottom right of box)
This channel should be auto-named 'Alpha 1' the image should go black
Click Edit - Fill...
Contents - Use: scroll to 'white'
Blending-normal, opacity-100%
Click ok
Now if you save as a TIFF or other alpha supported format, an alpha channel should be embedded in the file.

Hope this helps.

[Blue Ten]

Sorry for reviving an old thread, but I've finally found out how to get the result I was looking for. Select Color Range always caused too much loss of image data for me... and I wasn't quite sure how to pull off the vector mask trick. Thanks for the suggestions though, I think they pointed me in the right direction.

If you have a grayscale image (scanned line art, etc), navigate to the Channels palette and ctrl+click any of the channels. Then go to Select>Inverse, create a new layer, and Fill with black. Delete the old layer, and you've 'converted the grayscale image to alpha'.

This has worked perfectly for me each time without messing up the image or leaving behind solid bits of grays and whites.

To the custom Actions it goes :D.

I may have been unclear about what I was trying to do originally -- so I apologize if that was the case ^^;.