Nervovred

in_pic = "in.jpg"
out_pic = "out.jpg"
radius = 25 
size = "500x500"
bgcolor = "white" #JPG doesn't support alpha channel, write "None" if you want transparent edges for PNG files
cmd = "convert #{in_pic} " +
      "-resize #{size}! " + #comment out this line if you don't want to resize
      "\\( +clone -alpha extract " +
      "\\( -size #{radius}x#{radius} xc:black -draw 'fill white circle #{radius},#{radius} #{radius},0' " +
      "-write mpr:arc +delete \\) " +

Nervovred

in_pic = "in.jpg"
out_pic = "out.jpg"
radius = 25 
size = "500x500"
bgcolor = "None" #JPG doesn't support alpha channel, write "None" if you want transparent edges for PNG files
cmd = "convert #{in_pic} " +
					 "-resize #{size}! " + #comment out this line if you don't want to resize
					 "\\( +clone -alpha extract " +
					 "\\( -size #{radius}x#{radius} xc:black -draw 'fill white circle #{radius},#{radius} #{radius},0' -write mpr:arc +delete \\) " +
					 "\\( mpr:arc \\) -gravity northwest -composite " +