Making an image partly transparent

[tm2383]

Hi there. Can someone who is an expert with Gimp help me with a problem? I have pasted an image of an iridology chart below. I want to remove the white from this image altogether, so that the white layer is totally transparent. When I overlay this on the image of an iris, I will therefore be able to see the black lines and labels, but not the white, which will be transparent, showing the image of the eye that I have overlaid it on.

Also, is there a way of changing the colour of the black lines to another colour? This isn't essential, but it would be good if I could do this.

If you are able to help with my question, could you give me easy directions about how to do this, as I am not a regular Gimp user.

Thanks!

[Blighty]

A problem is that your image is not a good quality. The "white" background is a blotchy grey and the "black" is a blotchy charcoal. A better image will give better results.

1.
With the Colour Select tool with a Threshold of 60, select the black foreground. Looks like this:
https://imgur.com/a/0Yi9G

2.
Select > Invert

3. Edit > Clear (or press the Delete key). Looks like this:
https://imgur.com/623TOnw

4.
Select > None

5.
Set the Foreground Colour to red (or some other colour)

6.
Lock the Alpha Channel, like this:
https://imgur.com/BwIdjMf

7.
Bucket Fill the image with the set foregound colour
https://imgur.com/xY9TC7j

[rich2005]

Same post a few weeks ago

https://www.gimp-forum.net/Thread-Making...55#pid2555