Merge pull request #5 from trafi/feature/nsattributedstring

Support text drawing

Sources/ImageMod/NSAttributedString.swift

@@ -0,0 +1,54 @@
+import UIKit
+
+extension NSAttributedString: ImageModable {
+
+    public var mod: ImageMod {
+        ImageMod(info: .init(size()),
+                 draw: { info in
+                    self.with(info.tint)
+                        .with(info.drawRect.size)
+                        .with(info.shadow)
+                        .draw(in: info.drawRect)
+        })
+    }
+
+    private func with(_ tint: UIColor?) -> NSAttributedString {
+        guard let tint = tint else { return self }
+        return with(.foregroundColor, tint)
+    }
+
+    private func with(_ size: CGSize) -> NSAttributedString {
+
+        let currentSize = self.size()
+        let scale = min(size.width / currentSize.width, size.height / currentSize.height)
+
+        // https://developer.apple.com/documentation/foundation/nsattributedstring
+        let defaultFont = UIFont(name: "Helvetica", size: 12)!
+        let currentFont = attribute(.font, at: 0, effectiveRange: nil) as? UIFont ?? defaultFont
+
+        let font = currentFont.withSize(currentFont.pointSize * scale)
+
+        return with(.font, font)
+    }
+
+    private func with(_ shadow: (offset: CGPoint, blur: CGFloat, color: UIColor)?) -> NSAttributedString {
+
+        guard let shadow = shadow else { return self }
+
+        let nsShadow = NSShadow()
+        nsShadow.shadowOffset = CGSize(width: shadow.offset.x, height: shadow.offset.y)
+        nsShadow.shadowBlurRadius = shadow.blur
+        nsShadow.shadowColor = shadow.color
+
+        return with(.shadow, nsShadow)
+    }
+
+    private func with(_ key: NSAttributedString.Key, _ value: Any) -> NSAttributedString {
+
+        let mutable = NSMutableAttributedString(attributedString: self)
+        mutable.addAttribute(key, value: value,
+                             range: NSRange(location: 0, length: string.utf16.count))
+
+        return mutable
+    }
+}

Tests/ImageModTests/NSAttributedStringTests.swift

@@ -0,0 +1,33 @@
+import XCTest
+@testable import ImageMod
+
+final class NSAttributedStringTests: XCTestCase {
+
+    func test_itDraws() {
+
+        let sut = NSAttributedString(string: "Cats!")
+            .tinted(.blue)
+            .scaled(times: 4)
+            .shadowed(offset: CGPoint(x: 5, y: 10), blur: 20, color: .red)
+            .image
+
+
+        let image = UIGraphicsImageRenderer(size: CGSize(width: 152.5, height: 95.5)).image { context in
+
+            let shadow = NSShadow()
+            shadow.shadowOffset = CGSize(width: 5, height: 10)
+            shadow.shadowBlurRadius = 20
+            shadow.shadowColor = UIColor.red
+
+            let string = NSAttributedString(string: "Cats!", attributes: [
+                .foregroundColor: UIColor.blue,
+                .shadow: shadow,
+                .font: UIFont(name: "Helvetica", size: 48)!
+            ])
+
+            string.draw(at: CGPoint(x: 15, y: 10))
+        }
+
+        XCTAssertEqual(sut.pngData(), image.pngData())
+    }
+}