Alpha masking scans in Gimp and PS

[Gidde]

We should change the title of this thread to "how to make a scanned layer transparent" or something and move it to the tut section.

[ravells]

Good idea, Gidde - done!

[RobA]

My preferred method is to use inverse of the image as a layer mask.

That is also the easiest way to turn a B&W image into a mono-tint. After creating the layer mask flood fill the layer with a desired colour.

-Rob A>

[Sarsaparilla]

I figured something out, oh, I don't know about a month ago, that I should have known about a year ago. I wouldn't say anything except it might help someone else coming along the same path.

I can tell you that I didn't know about this until I read your post and it has already helped me.

One further note: while experimenting with removing the background from color images, I discovered that the "Color to Alpha" filter was making the foreground partially transparent, which was not good for my purposes. After some experimentation and some googling, I discovered that the same filter can be applied with a brush for a more precise application. Select the paintbrush tool, and then from the Mode dropdown, choose "Color Erase."

It makes me wonder how many other features I'm overlooking.

[RobA]

I can tell you that I didn't know about this until I read your post and it has already helped me.

One further note: while experimenting with removing the background from color images, I discovered that the "Color to Alpha" filter was making the foreground partially transparent, which was not good for my purposes. After some experimentation and some googling, I discovered that the same filter can be applied with a brush for a more precise application. Select the paintbrush tool, and then from the Mode dropdown, choose "Color Erase."

It makes me wonder how many other features I'm overlooking.

it doesn't actually make the foreground transparent, but it will make components that match transparent by the degree they match. So if you have a greyscale image then do a colour to transparent and pick white, they grey that has 50% white gets turned into black that is 50% transparent....

-Rob A>

[Sarsaparilla]

To be more clear: in the specific case I was working with, the paper color was too similar to the parts I wanted to keep, and therefore it was making my image too transparent (and also altering the color balance.) But I bet that result is fairly common any time someone is working with an image that isn't completely black and white.

I tried masking with a selection before applying the filter, but the results weren't satisfactory. The paintbrush version seems to help.