Marker with transparent part

I'm currently working on a logistics application. With Delphi XE8 and TMS Maps. Works great, but I have a problem with markers generated in the program.
I prepare a Base64 code, somehow I'm missing some thing in Format or what ever in that code.
The difficulty I'm having is that the markers are drawn as desired except that I have a clWhite rectangle around each marker. See the picture below. The blue one are generatetd by my Application the Yelow markers are downloaded from some homepage. Maybe someone can give me a hint how to make this clWhite area transparent. Thanks in advance HeWy

How are you generating Base64 version and what type is the icon? Is it a PNG, a BMP? Note that if you want to apply markers with transparency you need to make sure that the icon data includes Transparency, or you could also use SVG.

Hi Pieter,
Thanks for you reply.
I attached Base64 Marker code and my marker generator. Hope this shows how I tried to make the markers.

Base64 Markers.txt (4.0 KB)
MarkerGenerator.txt (1.8 KB)

Eventually TMS has already some component to generate markers based on size color and so on.

The issue lies in the code that generates the bitmap. It doesn't contain transparency information, and is not suitable for drawing as marker image with a transparent background. Please revise the code in "MarkerGenerator.txt" to properly introduce transparency in your image data.

Thanks very much, your hint helped me to solve the issue.
Solution is convert the Markericon to png
png := TPngImage.Create;
png.Assign( BtMp );
An the create a Base64 from that.
Issue soled thanks again