feat(camera): share jpeg transcoder + default maxWidth

apps/shared/ClawdisKit/Sources/ClawdisKit/JPEGTranscoder.swift

@@ -0,0 +1,93 @@
+import CoreGraphics
+import Foundation
+import ImageIO
+import UniformTypeIdentifiers
+
+public enum JPEGTranscodeError: LocalizedError, Sendable {
+    case decodeFailed
+    case propertiesMissing
+    case encodeFailed
+
+    public var errorDescription: String? {
+        switch self {
+        case .decodeFailed:
+            "Failed to decode image data"
+        case .propertiesMissing:
+            "Failed to read image properties"
+        case .encodeFailed:
+            "Failed to encode JPEG"
+        }
+    }
+}
+
+public struct JPEGTranscoder: Sendable {
+    public static func clampQuality(_ quality: Double) -> Double {
+        min(1.0, max(0.05, quality))
+    }
+
+    /// Re-encodes image data to JPEG, optionally downscaling so that the *oriented* pixel width is <= `maxWidthPx`.
+    ///
+    /// - Important: This normalizes EXIF orientation (the output pixels are rotated if needed; orientation tag is not
+    ///   relied on).
+    public static func transcodeToJPEG(
+        imageData: Data,
+        maxWidthPx: Int?,
+        quality: Double) throws -> (data: Data, widthPx: Int, heightPx: Int)
+    {
+        guard let src = CGImageSourceCreateWithData(imageData as CFData, nil) else {
+            throw JPEGTranscodeError.decodeFailed
+        }
+        guard
+            let props = CGImageSourceCopyPropertiesAtIndex(src, 0, nil) as? [CFString: Any],
+            let rawWidth = props[kCGImagePropertyPixelWidth] as? NSNumber,
+            let rawHeight = props[kCGImagePropertyPixelHeight] as? NSNumber
+        else {
+            throw JPEGTranscodeError.propertiesMissing
+        }
+
+        let pixelWidth = rawWidth.intValue
+        let pixelHeight = rawHeight.intValue
+        let orientation = (props[kCGImagePropertyOrientation] as? NSNumber)?.intValue ?? 1
+
+        guard pixelWidth > 0, pixelHeight > 0 else {
+            throw JPEGTranscodeError.propertiesMissing
+        }
+
+        let rotates90 = orientation == 5 || orientation == 6 || orientation == 7 || orientation == 8
+        let orientedWidth = rotates90 ? pixelHeight : pixelWidth
+        let orientedHeight = rotates90 ? pixelWidth : pixelHeight
+
+        let maxDim = max(orientedWidth, orientedHeight)
+        let targetMaxPixelSize: Int = {
+            guard let maxWidthPx, maxWidthPx > 0 else { return maxDim }
+            guard orientedWidth > maxWidthPx else { return maxDim } // never upscale
+
+            let scale = Double(maxWidthPx) / Double(orientedWidth)
+            return max(1, Int((Double(maxDim) * scale).rounded(.toNearestOrAwayFromZero)))
+        }()
+
+        let thumbOpts: [CFString: Any] = [
+            kCGImageSourceCreateThumbnailFromImageAlways: true,
+            kCGImageSourceCreateThumbnailWithTransform: true,
+            kCGImageSourceThumbnailMaxPixelSize: targetMaxPixelSize,
+            kCGImageSourceShouldCacheImmediately: true,
+        ]
+
+        guard let img = CGImageSourceCreateThumbnailAtIndex(src, 0, thumbOpts as CFDictionary) else {
+            throw JPEGTranscodeError.decodeFailed
+        }
+
+        let out = NSMutableData()
+        guard let dest = CGImageDestinationCreateWithData(out, UTType.jpeg.identifier as CFString, 1, nil) else {
+            throw JPEGTranscodeError.encodeFailed
+        }
+        let q = self.clampQuality(quality)
+        let encodeProps = [kCGImageDestinationLossyCompressionQuality: q] as CFDictionary
+        CGImageDestinationAddImage(dest, img, encodeProps)
+        guard CGImageDestinationFinalize(dest) else {
+            throw JPEGTranscodeError.encodeFailed
+        }
+
+        return (out as Data, img.width, img.height)
+    }
+}