Add conveniences to size an image view preserving its image's aspect ratio

Paralayout/UIImageView+Sizing.swift

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+//
+//  Copyright © 2024 Block, Inc.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+import UIKit
+
+extension UIImageView {
+
+    /// Returns the largest size that will fit within the specified available `sizeToFit`, preserving the receiver's `image`'s aspect ratio.
+    ///
+    /// If `allowUpscaling` is true, the returned size will be at most the image's native size. This is most commonly used when the `image` is a raster image and is not meant to be scaled up.
+    public func sizeThatFitsPreservingAspectRatio(_ sizeToFit: CGSize, allowingUpscaling: Bool) -> CGSize {
+        guard let image else {
+            return .zero
+        }
+
+        if !allowingUpscaling, image.size.width <= sizeToFit.width, image.size.height <= sizeToFit.height {
+            return image.size
+        } else {
+            return image.size.aspectRatio.size(toFit: sizeToFit, in: self)
+        }
+    }
+
+    /// Returns the largest size that will fit within the specified available `width` and `height`, preserving the receiver's `image`'s aspect ratio.
+    ///
+    /// If `allowUpscaling` is true, the returned size will be at most the image's native size. This is most commonly used when the `image` is a raster image and is not meant to be scaled up.
+    public func sizeThatFitsPreservingAspectRatio(width: CGFloat, height: CGFloat = .greatestFiniteMagnitude, allowingUpscaling: Bool) -> CGSize {
+        sizeThatFitsPreservingAspectRatio(CGSize(width: width, height: height), allowingUpscaling: allowingUpscaling)
+    }
+
+    /// Sets the size of the receiver's `bounds` such that it will fit within the specified available `sizeToFit`, preserving the receiver's `image`'s aspect ratio.
+    ///
+    /// If `allowUpscaling` is true, the resulting size will be at most the image's native size. This is most commonly used when the `image` is a raster image and is not meant to be scaled up.
+    public func sizeToFitPreservingAspectRatio(_ sizeToFit: CGSize, allowingUpscaling: Bool) {
+        bounds.size = sizeThatFitsPreservingAspectRatio(sizeToFit, allowingUpscaling: allowingUpscaling)
+    }
+
+    /// Sets the size of the receiver's `bounds` such that it will fit within the specified available `width` and `height`, preserving the receiver's `image`'s aspect ratio.
+    ///
+    /// If `allowUpscaling` is true, the resulting size will be at most the image's native size. This is most commonly used when the `image` is a raster image and is not meant to be scaled up.
+    public func sizeToFitPreservingAspectRatio(width: CGFloat, height: CGFloat = .greatestFiniteMagnitude, allowingUpscaling: Bool) {
+        sizeToFitPreservingAspectRatio(CGSize(width: width, height: height), allowingUpscaling: allowingUpscaling)
+    }
+
+}