Turning a color transparent in Photoshop?

[Asha]

I have an image which is mostly black lines on a white background, and I'd like to make the background transparent. However, using (in Photoshop) Magic Eraser or clearing with Magic Wand leaves grey spots behind... I've tried changing anti-aliasing and tolerance values, but it's still a little messy, though. But since it's only black and white and values in between, though, is there an option to simply swap "white" to "transparent" - so that "50% grey" becomes "black with 50% opacity" (or equivalent) - etc.? Sorry if it's completely obvious (or obviously impossible) - thanks in advance.

[budafist]

If you are intending to put the artwork onto another layer, you can set the layer to multiply and this will make all the white parts of the layer transparent.

[adamblan]

You could also try "Replace Color" , or select a color range & apply a mask... but changing the blending mode to multiply / screen & placing it over a white / black layer is going to be the easiest. ^ :rolleyes:

[urstwile]

Put it on a new layer, and set the transparency to darken.

[Treefrog]

Setting transparancy to Multiply or Darken would be my first choice also. But if that was not suitable, I suggest creating a new solid colour layer in black, and copy and paste your b/w image into this layer (option-click on the layer mask and paste it here.) The resulting mask will need to be inverted. I do this alot for handdrawn key-lines around coloured drawings, it works great.

[Broacher]

Agree with Multiply option for first choice-- if you want the black ink to be JUST black ink though, be sure you're working in CMYK (otherwise, it'll be a blend).

If you wanted to truly make a layer "so that "50% grey" becomes "black with 50% opacity" (or equivalent)" -- it's a different spec, but there's a filter you can Google for called "Eliminate White' that does this nicely. Essentially, it translates a layer's luminosity to layer mask, and then applies the mask to the layer and deletes the mask.

[seosamh]

agree multiply is good for getting rid of white. also as a side note, shift - and shift + scrolls through the different blending modes of a selected layer. good wee shortcut that.

[Broacher]

So that's what happened the Alt-shft blend mode shortcuts. Ah well. Progress, I suppose.

[seosamh]

So that's what happened the Alt-shft blend mode shortcuts. Ah well. Progress, I suppose.
yip nothing worse than getting rid of something you use, the removal of the way linking layers worked in from about 3 to cs melted my brain! i now grudgingly accept folders are better! :D

[Broacher]

I've always been a big fan of folders, and I'm glad that they've leaned that way in the Layer UI.

You know, when you think about, the Pshop Layer Palette may just be the most sophisticated and powerful piece of screen real estate most people will ever see. The UI architecture in this thing by any measure, is very impressive.

[NTLemon]

When you think about it for a second its pretty impressive how much you can do with the layers palette in PS compared to layers palettes from other programs. Also, I would go insane without folders.

[urstwile]

I love folders as well.

Another method for turning a black and white object to transparent on the white area is to option drag the blend if sliders in the Blend If options.

Before:

http://i34.tinypic.com/23ld1d3.jpg

After:

http://i37.tinypic.com/358z02c.jpg

[Asha]

Thanks for the help, everyone - "Multiply" worked like a charm. Thank you again!