I have been looking for a way to convert a 2D png file to 3D print file and using a toolchain of 4 standard programs I am now able to do it. My sport is judo and these are the characters for the word JUDO. I made a keychain and printed it in two colours. First I print it with white until 50 percent (when the bottom layer is ready) and then I pause the print, change the filament to black en continue the print. The result is a nice keychain with good solid lines for the logo. The toolchain is "Image To 3D Converter", 3d-Builder, FreeCad and cura. I will describe the steps on my site in a few days.
I change the filament at 50 percent of the print to the other (forground) colour.