CGImageAlphaInfo.alphaOnly There is no color data, only an alpha channel. Declarationcase alphaOnly See AlsoConstantsCGImageAlphaInfo.firstCGImageAlphaInfo.lastCGImageAlphaInfo.noneCGImageAlphaInfo.noneSkipFirstCGImageAlphaInfo.noneSkipLastCGImageAlphaInfo.premultipliedFirstCGImageAlphaInfo.premultipliedLast