I am getting unsupported parameter combination CGBitmap error with swift

Question

I am trying to create a CGContext in swift. It compiles but throws an error at runtime.

let colorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
let conte         


        

Answer 1

Just in case somebody is running into the same problem. The snippet below finally works.

let colorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue)
let context = CGBitmapContextCreate(nil, UInt(rect.size.width), UInt(rect.size.height), 8, 0, colorSpace, bitmapInfo)

It generates a 32 bit RGBA context in swift

Answer 2

Suggested way compatible with both Xcode 8.3 and Xcode 9 which supports Swift 3 and Swift 4

let colorSpace = CGColorSpaceCreateDeviceRGB()
guard let bitmapContext = CGContext(data: nil, 
                                    width: Int(size.width),
                                    height: Int(size.height),
                                    bitsPerComponent: Int(bitsPerComponent),
                                    bytesPerRow: Int(bytesPerRow),
                                    space: colorSpace,
                                    bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else {
                                  return nil
    }

Answer 3

I had some issues in Swift 1.2 using UInt, now I'm using Int and it's working. This Example shows how to convert an Image to a grayscale image.

let imageRect = self.myImage.frame

let colorSpace = CGColorSpaceCreateDeviceGray()
let width = imageRect.width
let height = imageRect.height

let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.None.rawValue)
let context = CGBitmapContextCreate(nil, Int(width), Int(height), 8, 0, colorSpace, bitmapInfo)

Answer 4

In Swift 2.1 one can access the fields properly, and even OR them together:

let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue)

let context = CGBitmapContextCreate(baseAddress, width, height, 8,
                bytesPerRow, colorSpace, bitmapInfo.rawValue);

Whole lot of 'rawValue' going on :)

You don't even need to separate out the bitmapInfo, and can do a one-liner:

let context = CGBitmapContextCreate(baseAddress, width, height, 8,
                bytesPerRow, colorSpace, CGImageAlphaInfo.PremultipliedFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue

Answer 5

Updated for Swift 5:

 let colorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
 let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
 let context = CGContext(data: nil, width: UInt(rect.size.width), height: UInt(rect.size.height), bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)

where rect has height and width

Answer 6

In Swift 2.2:

let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedLast.rawValue).rawValue
let colorSpace = CGColorSpaceCreateDeviceRGB()
let context = CGBitmapContextCreate(nil, Int(width), Int(height), 8, 0, colorSpace, bitmapInfo)