在Objective-C中，CGBitmapInfo包含:kCGBitmapAlphaInfoMask=0x1F,kCGBitmapFloatInfoMask=0xF00,kCGBitmapFloatComponents=(1但是，在Swift3.0中，CGBitmapInfo删除了kCGBitmapByteOrderDefault:publicstructCGBitmapInfo:OptionSet{publicinit(rawValue:UInt32)publicstaticvaralphaInfoMask:CGBitmapInfo{get}publicstaticvarfloat