Is there a way to know if an Emoji is supported in iOS?

问题

I'm building an iOS App, and Emojis play a big part in it.

In iOS 10.2, new emojis were released.

I'm pretty sure that if someone has iOS 8, for example, they wouldn't actually be able to see these emojis. Is there a way to detect this? I'm trying to dynamically build a list of all the Emojis that are supported on the user's iOS version, but I'm having a bit of trouble.

回答1:

Clarification: an Emoji is merely a character in the Unicode Character space, so the present solution works for all characters, not just Emoji.

Synopsis

To know if a Unicode character (including an Emoji) is available on a given device or OS, run the unicodeAvailable() method below.

It works by comparing a given character image against a known undefined Unicode character U+1FFF.

unicodeAvailable(), a `Character` extension

private static let refUnicodeSize: CGFloat = 8
private static let refUnicodePng =
    Character("\u{1fff}").png(ofSize: Character.refUnicodeSize)

func unicodeAvailable() -> Bool {
    if let refUnicodePng = Character.refUnicodePng,
        let myPng = self.png(ofSize: Character.refUnicodeSize) {
        return refUnicodePng != myPng
    }
    return false
}

Discussion

All characters will be rendered as a png at the same size (8) as defined once in

static let refUnicodeSize: CGFloat = 8
The undefined character U+1FFF image is calculated once in

static let refUnicodePng = Character("\u{1fff}").png(ofSize: Character.refUnicodeSize)
A helper method optionally creates a png from a Character

func png(ofSize fontSize: CGFloat) -> Data?

1. Example: Test against 3 emoji

let codes:[Character] = ["\u{2764}","\u{1f600}","\u{1F544}"] // ❤️, 😀, undefined
for unicode in codes {
    print("\(unicode) : \(unicode.unicodeAvailable())")
}

2. Example: Test a range of Unicode characters

func unicodeRange(from: Int, to: Int) {
    for unicodeNumeric in from...to {
        if let scalar = UnicodeScalar(unicodeNumeric) {
            let unicode = Character(scalar)
            let avail = unicode.unicodeAvailable()
            let hex = String(format: "0x%x", unicodeNumeric)
            print("\(unicode) \(hex) is \(avail ? "" : "not ")available")
        }
    }
}

Helper function: `Character` to png

func png(ofSize fontSize: CGFloat) -> Data? {
    let attributes = [NSAttributedStringKey.font:
                          UIFont.systemFont(ofSize: fontSize)]
    let charStr = "\(self)" as NSString
    let size = charStr.size(withAttributes: attributes)

    UIGraphicsBeginImageContext(size)
    charStr.draw(at: CGPoint(x: 0,y :0), withAttributes: attributes)

    var png:Data? = nil
    if let charImage = UIGraphicsGetImageFromCurrentImageContext() {
        png = UIImagePNGRepresentation(charImage)
    }

    UIGraphicsEndImageContext()
    return png
}

► Find this solution on GitHub and a detailed article on Swift Recipes.

来源：https://stackoverflow.com/questions/41318999/is-there-a-way-to-know-if-an-emoji-is-supported-in-ios

标签

ios

emoji