Auto-detect window corner radius; anti-alias the mask

Measure the picked window's real corner radius from the capture itself
(the crop's corner pixels are the desktop background; app content starts
where the color departs), correct for arc anti-aliasing, and fall back to
10pt when ambiguous. The clip mask is supersampled 3x for smooth edges.

💘 Generated with Crush

Assisted-by: Crush:deepseek-v4-flash-0731

Sources/Kapture/CaptureController.swift

@@ -372,6 +372,41 @@ final class ScreenCapture {
 
     private init() {}
 
+    /// Estimate the window's corner radius (in image pixels) by scanning the
+    /// top-left corner: the crop's corner pixels are the desktop background;
+    /// app content starts where the color departs from it.
+    static func detectCornerRadius(of image: CGImage) -> CGFloat? {
+        let w = image.width, h = image.height
+        guard w > 30, h > 30 else { return nil }
+        var px = [UInt8](repeating: 0, count: w * h * 4)
+        guard let c = CGContext(data: &px, width: w, height: h, bitsPerComponent: 8, bytesPerRow: w * 4,
+            space: CGColorSpaceCreateDeviceRGB(),
+            bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else { return nil }
+        c.draw(image, in: CGRect(x: 0, y: 0, width: w, height: h))
+
+        func pixel(x: Int, yTop: Int) -> (r: Int, g: Int, b: Int) {
+            let row = yTop * w * 4 + x * 4
+            return (Int(px[row]), Int(px[row + 1]), Int(px[row + 2]))
+        }
+        let bg = pixel(x: 0, yTop: 0)
+        func diffFromBg(_ p: (r: Int, g: Int, b: Int)) -> Int {
+            abs(p.r - bg.r) + abs(p.g - bg.g) + abs(p.b - bg.b)
+        }
+        var radii: [CGFloat] = []
+        for (limit, axis) in [(h / 3, 0), (w / 3, 1)] {
+            for i in 0..<limit {
+                let p = axis == 0 ? pixel(x: 0, yTop: i) : pixel(x: i, yTop: 0)
+                if diffFromBg(p) > 24 {
+                    radii.append(CGFloat(i))
+                    break
+                }
+            }
+        }
+        guard radii.count == 2 else { return nil }
+        let r = (radii[0] + radii[1]) / 2
+        return (r >= 3 && r <= 40) ? r : nil
+    }
+
     @available(macOS 14.0, *)
     private func crop(_ image: CGImage, to cgRect: CGRect, display: SCDisplay, roundedCorners: Bool = false) -> CGImage? {
         // cgRect is in SCDisplay space (bottom-left origin, Y flipped vs AppKit).
@@ -402,19 +437,34 @@ final class ScreenCapture {
         // Apply a rounded-corner alpha mask for window captures, matching
         // macOS window chrome (≈10pt radius, scaled to image pixels).
         if roundedCorners {
-            // Clip to a rounded rect and redraw — deterministic corner alpha
-            // (masking() can fail depending on the source pixel format).
-            let radius = 10 * scaleX
-            guard let ctx = CGContext(
+            // The screen crop contains the app's real rounded corners against
+            // the desktop — measure the radius from the corner pixels, then
+            // mask with it (supersampled for smooth edges).
+            let detected = Self.detectCornerRadius(of: result)
+            let radius = min(max((detected.map { $0 * 1.23 + 2.6 }) ?? (10 * scaleX), 4), 40)
+            CaptureController.log("corners: detected=\(detected.map { String(format: "%.1f", $0) } ?? "nil") using=\(Int(radius))px")
+            let ss = 3
+            let W = result.width * ss, H = result.height * ss
+            guard let hiCtx = CGContext(
+                data: nil, width: W, height: H,
+                bitsPerComponent: 8, bytesPerRow: 0,
+                space: CGColorSpaceCreateDeviceRGB(),
+                bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
+            ) else { return result }
+            hiCtx.addPath(CGPath(roundedRect: CGRect(x: 0, y: 0, width: W, height: H), cornerWidth: radius * CGFloat(ss), cornerHeight: radius * CGFloat(ss), transform: nil))
+            hiCtx.clip()
+            hiCtx.interpolationQuality = .high
+            hiCtx.draw(result, in: CGRect(x: 0, y: 0, width: W, height: H))
+            guard let hi = hiCtx.makeImage(),
+                  let downCtx = CGContext(
                 data: nil, width: result.width, height: result.height,
                 bitsPerComponent: 8, bytesPerRow: 0,
                 space: CGColorSpaceCreateDeviceRGB(),
                 bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
             ) else { return result }
-            ctx.addPath(CGPath(roundedRect: CGRect(x: 0, y: 0, width: result.width, height: result.height), cornerWidth: radius, cornerHeight: radius, transform: nil))
-            ctx.clip()
-            ctx.draw(result, in: CGRect(x: 0, y: 0, width: result.width, height: result.height))
-            if let masked = ctx.makeImage() {
+            downCtx.interpolationQuality = .high
+            downCtx.draw(hi, in: CGRect(x: 0, y: 0, width: result.width, height: result.height))
+            if let masked = downCtx.makeImage() {
                 result = masked
             }
         }

build-app.sh

@@ -108,9 +108,9 @@ cat > "$APP/Contents/Info.plist" <<'PLIST'
     <key>CFBundleIconFile</key>
     <string>Icon</string>
     <key>CFBundleShortVersionString</key>
-    <string>1.8.4</string>
+    <string>1.8.5</string>
     <key>CFBundleVersion</key>
-    <string>84</string>
+    <string>85</string>
     <key>LSUIElement</key>
     <true/>
     <key>NSHighResolutionCapable</key>