Transforming white parts of geotiff into a transparent background/ deleting it?

Hello,

I have a lot of geotiffs that I want to import into a map project. Unfortunately these blueprints are framed by a white background, which I would like to transform into a transparent one. Basically I only want to keep the lines, that make up these blueprints.

I imagine the required steps somewhat like this:

1. Select the background. Since every blueprint has a different shape, i would try try to detect the background-pixels by colour (white). Possible drawback: Single pixels in the needed Picture could also be white and therefore be falsely selected. Is there a transformer for this you would recommend?How else could I differentiate the needed parts of the geotiff?
2. Delete the selected pixels or turn them transparent.
3. Another issue that I worry about: The thin, dark lines of the blueprints might hardly be visible on an orthophoto-based map. Can I somehow change the colour of my outcome?

Since I am new to FME, I wonder which transformers I should use. If you are experienced with similar projects, please let me know how you solved this.

Thanks!