Image to Textured Anulus (Ring) Python Tool

originally this was a script to convert images to height maps as polyhedrons suitable for use in openscad...now it has become a tool for making height map textured ring shapes

ToDo
add control for fading edges of image

v0-13
modifications based on prototype from i.materialise
Ring .stl internal diameter seemed to be 6 or 16.5mm, but size is entered correctly as 6.5 or 16.9mm which is correct
GENERATING A NON-TEXTURED RING GIVES CORRECT DIMENSIONS however adding an embossed texture to the inside adds material
Fixed!!!
in... if texture:
if texture_inside_not_outside:
#print "texture inside not outside"
if texture_engraved_not_raised:
#changes made here to fix texture size issue
NOW vertex_list.append([row*height_scaling,column,texture_depth - (pix[row,column]*depth_scaling) ])
WAS vertex_list.append([row*height_scal