Extend Bitmap with initializer from UIImage and export to UIImage

Sources/geometrize/Bitmap+UIImage.swift

@@ -0,0 +1,63 @@
+import Foundation
+
+#if canImport(UIKit)
+
+import UIKit
+
+extension Bitmap {
+
+    public init?(image: UIImage) {
+        guard let cgImage = image.cgImage else { return nil }
+
+        // Redraw image for correct pixel format
+
+        let colorSpace = CGColorSpaceCreateDeviceRGB()
+        var bitmapInfo: UInt32 = CGBitmapInfo.byteOrder32Big.rawValue
+            | CGImageAlphaInfo.premultipliedLast.rawValue & CGBitmapInfo.alphaInfoMask.rawValue
+
+        let width = Int(image.size.width)
+        let height = Int(image.size.height)
+        let size = width * height
+        let imageData = UnsafeMutablePointer<UInt8>.allocate(capacity: size)
+        defer { imageData.deallocate() }
+
+        guard let imageContext = CGContext(
+            data: imageData,
+            width: width,
+            height: height,
+            bitsPerComponent: 8,
+            bytesPerRow: width * 4,
+            space: colorSpace,
+            bitmapInfo: bitmapInfo
+        ) else { return nil }
+
+        imageContext.draw(cgImage, in: CGRect(origin: .zero, size: image.size))
+        let bufferPointer = UnsafeMutableBufferPointer<UInt8>(start: imageData, count: size)
+
+        self.init(width: width, height: height, data: Array(bufferPointer))
+    }
+
+    public func uiImage() -> UIImage? {
+        let colorSpace = CGColorSpaceCreateDeviceRGB()
+        var bitmapInfo: UInt32 = CGBitmapInfo.byteOrder32Big.rawValue |
+            CGImageAlphaInfo.premultipliedLast.rawValue & CGBitmapInfo.alphaInfoMask.rawValue
+        var mutableBacking = backing
+        return mutableBacking.withUnsafeMutableBufferPointer() {
+            CGContext(
+                data: $0.baseAddress,
+                width: width,
+                height: height,
+                bitsPerComponent: 8,
+                bytesPerRow: width * 4,
+                space: colorSpace,
+                bitmapInfo: bitmapInfo,
+                releaseCallback: nil,
+                releaseInfo: nil
+            )?
+            .makeImage()
+            .flatMap(UIImage.init(cgImage:))
+        }
+    }
+}
+
+#endif