Setting A CGContext Transparent Background

Question

I am still struggling with drawing a line with CGContext. I have actually go to line to draw, but now I need the background of the Rect to be transparent so the existing ba

Answer 1

Init a context with opaque == false, Swift 3

UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.main.scale) 

opaque

A Boolean flag indicating whether the bitmap is opaque. If you know the bitmap is fully opaque, specify true to ignore the alpha channel and optimize the bitmap’s storage. Specifying false means that the bitmap must include an alpha channel to handle any partially transparent pixels.