util: add ImageResizer to change size of images

damus/Models/Camera/ImageResizer.swift

@@ -0,0 +1,40 @@
+//
+//  ImageResizer.swift
+//  damus
+//
+//  Created by Suhail Saqan on 8/5/23.
+//
+
+import Foundation
+import UIKit
+
+public enum ImageResizingError: Error {
+    case cannotRetrieveFromURL
+    case cannotRetrieveFromData
+}
+
+public struct ImageResizer {
+    public var targetWidth: CGFloat
+
+    public init(targetWidth: CGFloat) {
+        self.targetWidth = targetWidth
+    }
+
+    public func resize(at url: URL) -> UIImage? {
+        guard let image = UIImage(contentsOfFile: url.path) else {
+            return nil
+        }
+
+        return self.resize(image: image)
+    }
+
+    public func resize(image: UIImage) -> UIImage {
+        let originalSize = image.size
+        let targetSize = CGSize(width: targetWidth, height: targetWidth*originalSize.height/originalSize.width)
+        let renderer = UIGraphicsImageRenderer(size: targetSize)
+        return renderer.image { (context) in
+            image.draw(in: CGRect(origin: .zero, size: targetSize))
+        }
+    }
+}
+