CODEWITHSUNDEEP
swiftcore-graphics
a_tuo
a_tuo

Reputation: 659

Why CGBitmapInfo remove the kCGBitmapByteOrderDefault which in Objective-C?

In Objective-C, the CGBitmapInfo contains:

kCGBitmapAlphaInfoMask = 0x1F,
kCGBitmapFloatInfoMask = 0xF00,
kCGBitmapFloatComponents = (1 << 8),
kCGBitmapByteOrderMask     = kCGImageByteOrderMask,
kCGBitmapByteOrderDefault  = (0 << 12),
kCGBitmapByteOrder16Little = kCGImageByteOrder16Little,
kCGBitmapByteOrder32Little = kCGImageByteOrder32Little,
kCGBitmapByteOrder16Big    = kCGImageByteOrder16Big,
kCGBitmapByteOrder32Big    = kCGImageByteOrder32Big

However, in Swift 3.0, CGBitmapInfo removed the kCGBitmapByteOrderDefault:

public struct CGBitmapInfo : OptionSet {

    public init(rawValue: UInt32)
    public static var alphaInfoMask: CGBitmapInfo { get }
    public static var floatInfoMask: CGBitmapInfo { get }
    public static var floatComponents: CGBitmapInfo { get }
    public static var byteOrderMask: CGBitmapInfo { get }
    public static var byteOrder16Little: CGBitmapInfo { get }
    public static var byteOrder32Little: CGBitmapInfo { get }
    public static var byteOrder16Big: CGBitmapInfo { get }
    public static var byteOrder32Big: CGBitmapInfo { get }
}

That's why?

Can I init the CGBitmapInfo like CGBitmapInfo(rawValue: 0) to replace the kCGBitmapByteOrderDefault?

Upvotes: 2

Views: 1894

Answers (2)

N3SS4H
N3SS4H

Reputation: 561

see CGBitmapInfo or CGImageByteOrderInfo https://developer.apple.com/documentation/coregraphics/cgimagebyteorderinfo https://developer.apple.com/documentation/coregraphics/cgbitmapinfo

As long as the 3 bits in the ByteOrderMask are 0, you are good. I have not found any doc stating what a byte order of 0 does. The following result in the same 0 value. 

let b: CGBitmapInfo = []
let b = CGBitmapInfo(rawValue: 0)

111000000000000 byteOrder mask

you can grab the possible values for ByteOrder from 

001000000000000 == CGBitmapInfo.byteOrder16Little.rawValue 
010000000000000 == CGBitmapInfo.byteOrder32Little.rawValue 
011000000000000 == CGBitmapInfo.byteOrder16Big.rawValue 
100000000000000 == CGBitmapInfo.byteOrder32Big.rawValue

example setting value 

let b: CGBitmapInfo = [ .byteOrder32Big]
print("\(b.contains(.byteOrder32Big))") // true
print("\(b.contains(.byteOrder16Little))") // false
print("\(b.rawValue)") // 16384

Upvotes: 1

OOPer
OOPer

Reputation: 47886

Can I init the CGBitmapInfo like CGBitmapInfo(rawValue: 0) to replace the kCGBitmapByteOrderDefault?

The answer is YES.

Swift omits some 0-value enum label in some cases. (details depend on the version of Swift).

If you find some enum label is not imported into Swift, check the original source in Objective-C and confirm it really has integer value 0, then replace it with init(rawValue: 0).

ADDED

I cannot have found much about That's why?, only one you can find is in the Xcode Release Notes (>Xcode 8.0>Swift):

  • The None members of imported NS_OPTIONS option sets are marked as unavailable when they are imported. Use [] to make an empty option set, instead of a None member.

It is not clear enough what None member means, but it seems the designer of Swift importer prefers the empty set literal [] for OptionSet types when representing default or none.

So, the first half of this answer should be modified:

You can use CGBitmapInfo(rawValue: 0) to replace kCGBitmapByteOrderDefault, but the empty set literal is preferred:

let myBitmapInfo: CGBitmapInfo = []

Upvotes: 3

Related Questions