New version 1.1.1 available.

I updated all dependancies and I tried to fix the bug on images with more of 8 bits by color component.
Inversed vertical gradient on svg is fixed too.

@BIRBANTE
I don't understand the problem.
Unfortunately, even if we start from a 24-bit BMP file and converted it to NNG Bitmap with the program, it does not work, we still see the icons with a black background.
A 24bits bmp do not have an alpha layer so in the converted image you do not have it too.
If you use a 32bits bmp with alpha the converted will be with alpha too.
Alpha layer is optional on nng bitmap, to get a smaller file I do not add an useless alpha layer.

I found a big bug on photoshop, when you convert an image with photoshop to a 32 bits bmp an alpha mask full transparent is applied on the image.
Gimp do not have the bug.