after codeing my app form vb to lazarus useing vampire imageing library I found that when running it uses 100% of the cpu which strikes me as odd as my vb app uses less then 10% and I thought free pascal and the gcc compiler would make a lot more effecient code. This sent me back to the drawing board, While dreaming up a way to do what I need without useing vampire imageing library I may have discovered something that can help you.
I use windows so I don't know if it holds true with linux lazarus.
If you take the bitmap into an editor, I used paint.net and pick the color $00ffffff or ffffff which in is 255 255 255 solid white and use the bucket to make the background of the bmp solid white then save this new bitmap and load it in lazarus then the Bitmap background will be transparent to the form color.
Been reading a lot and things that annoy me are posts like this
http://forum.lazarus.freepascal.org/index.php/topic,2939.0.htmlit's saying transpareny is implemented with a command like
image1.TransparentColor := Bitmap.Canvas.Pixels[0,0];
image1.Transparent := true;
this post is from 2006
the graphics wiki talks about how to make a transparnet bitmap but I've yet to find working code.
many many newer posts say alphablending and transparency ae not yet supported.