Yes, E_FORMAT_BYTE defines 8bit/1byte chars as input data type.
Concerning your other question about width&height, not really sure what you mean by that. 
If you are using the C interface, you don’t call any actual G’MIC function directly. You have to give the dimensions/length of the data pointer you pass to the call though, that is what these fields are for.
Thanks! I was referring to setting the width and height of input images like here in use_libgmic.c:
// Set the dimensions of the input image [0]
59 // (usually 'depth' will be '1' and 'spectrum' will be '4' for RGBA or '3' for RGB).
60 images[0].width = 500;
61 images[0].height = 500;
62 images[0].spectrum = 4;
63 images[0].depth = 1;
I wanted to build libgmic in visual studio. How can I do that?