HalfFloat.swift

/*
MIT License
Copyright 2018 Tobias Due Munk
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

extension UInt16 {
    var halfFloat: Float {
        // 1 bit sign
        // 5 bit exponent
        // 11 bit significand (10 bit explicitly stored)
        let sign = Float((self & 0b1000_0000_0000_0000) >> 15)
        let exponent = Float((self & 0b0111_1100_0000_0000) >> 10)
        let significand = Float(self & 0b0000_0011_1111_1111)

        if exponent == 0b0_0000 {
            if significand == 0 {
                return pow(-1, sign) * 0
            } else {
                // (−1)^signbit × 2^(−14) × 0.significantbits
                let last = 0 + significand / 0b0011_1111_1111
                return pow(-1, sign) * pow(2, -14) * last
            }
        } else if exponent == 0b1_1111 {
            if significand == 0 {
                return pow(-1, sign) * .infinity
            } else {
                return .nan
            }
        } else {
            // (−1)^signbit × 2^(exponent−15) × 1.significantbits
            let last = 1 + significand / 0b0011_1111_1111
            return pow(-1, sign) * pow(2, exponent - 15) * last
        }
    }
}

extension Float {
    var halfFloatBitPattern: UInt16 {
        var value = self

        let signBytes: UInt16
        if value.sign == .plus {
            signBytes = 0b0000_0000_0000_0000
        } else {
            signBytes = 0b1000_0000_0000_0000
            value *= -1
        }

        guard value.isNaN == false else {
            let exponentBytes: UInt16 = 0b1_1111
            let significandBytes: UInt16 = 0
            return signBytes | exponentBytes | significandBytes
        }

        guard value != 0 else {
            return signBytes
        }
        let exponent = log2(value).rounded(.down)
        let exponentBytes: UInt16
        let significandBytes: UInt16
        if exponent == 1 {
            exponentBytes = 0
            let significand = value * 1024
            significandBytes = UInt16(significand)
        } else if exponent == .infinity {
            exponentBytes = 0b1111 << 10
            significandBytes = 0
        } else if exponent <= -15 {
            exponentBytes = 0
            let significand = value * 1024
            significandBytes = UInt16(significand)
        } else {
            exponentBytes = UInt16(exponent + 15) << 10
            value /= pow(2, exponent)
            let significand = (value - 1) * 1024
            significandBytes = UInt16(significand)
        }
        return signBytes | exponentBytes | significandBytes
    }
}

Any chance you can pop a license on this? Thanks!

Yes I can. Sorry for the delay. Consider it MIT :)