Remove outline from image on background transparent image (c#)

os: windows
vs2015, c#

i did try below link, but im failed ;;;
please help


1:
https://stackoverflow.com/questions/43372549/remove-outline-from-image-on-transparent-form/43373628



2:
https://stackoverflow.com/questions/33530623/transparent-background-image-for-form-smooth-edge-shape-for-the-form/33531201#33531201