Change color but retain alpha transparency?

[slimshady]

Hello,

I have a .png image that contains an area of 58*41 pixels that I would like to change. The image itself is bigger, but I would only like to change these pixels.

Most of the pixels in that area are at least partly transparent, they have an aplha value of something between 170 and 255.

Now I would like to replace this image by another one. However, the other image is not transparent at all. So I would like to retain the aplha transparency values of the original image for that area and later assign them to the area I changed.

How can I do that?

Here is what I try to do if you need more info:

The windows 7 media center has some icons in its main menu that are used to show e.g. recorded TV or music library. These icons use images that MS chose. Here you can see one in action:

However, I would like to replace the things you see (e.g. the astronaut) by my own content (images of TV shows I watch, like Lost or Scrubs).

Now these images by MS look pretty cool and that is why I would like to have the same amout of transparency.

slimshady

[Sarkut]

slimshady,

You could try the Silhouette Plus plugin, set to default. (Black)

Apply it to the existing image.

Then, use it as an Alpha Mask with all boxes checkmarked

in the Alpha Mask effect window; apply it to the new image.

[slimshady]

Thanks for your answer, but I don't quite understand. How do I apply it to the existing image and where can I find alpha mask?

[Sarkut]

Have you already extracted the Win 7 icon images?

I don't have Windows 7 so can't help with that part.

Alpha Mask Import plugin:

Silhouette Plus:

Edited April 6, 2010 by Sarkut

[slimshady]

Yeah I have the Windows 7 icons extracted from a dll.

This is what I have done, is that correct:

Original image: I selected the area with alpha values I wanted to replace later, then I opened the silhoutte plus plugin and selected these options:

All Alpha less than 255

R: 0

G: 0

B: 0

Both sliders are at the very bottom.

This would create a black image, which pixels on the right having more transparency (the exact same alpha values the original had).

Than I would copy that area to the clipboard.

The image I want to place in the original image (after having adjusted its size):

I selected everything, then I selected the alpha mask plugin and checked all boxes, although "mix alpha" would not change anything I could see. (This image had no transparency if that matters).

Then the image had transparency and I copied it to the original image.

It looks pretty OK althoug a little bit dark to me, is this the procedure you meant?

[Sarkut]

Sounds right.