Optimize images with ImageOptim

Sources/Generator/Files/ImageGenerator.swift

@@ -18,6 +18,10 @@ private struct ImageJob {
 
 final class ImageGenerator {
 
+    private let imageOptimSupportedFileExtensions: Set<String> = ["jpg", "png", "svg"]
+
+    private let imageOptimizationBatchSize = 50
+
     /**
      The path to the input folder.
      */
@@ -66,6 +70,11 @@ final class ImageGenerator {
      */
     private var generatedImages: Set<String> = []
 
+    /**
+     The images optimized by ImageOptim
+     */
+    private var optimizedImages: Set<String> = []
+
     /**
      A cache to get the size of source images, so that files don't have to be loaded multiple times.
 
@@ -182,8 +191,9 @@ final class ImageGenerator {
             create(images: jobs, from: source)
             count += 1
         }
-        print(String(format: "                                     \r", count, imageJobs.count), terminator: "")
+        print("                                     \r", terminator: "")
         createMultiImages()
+        optimizeImages()
         printMissingImages()
         printImageWarnings()
         printGeneratedImages()
@@ -360,7 +370,7 @@ final class ImageGenerator {
             createMultiImages(from: baseImage, path: path)
             count += 1
         }
-        print(String(format: "                                     \r", count, sort.count), terminator: "")
+        print("                                     \r", terminator: "")
     }
 
     private func createMultiImages(from source: String, path: String) {
@@ -414,4 +424,33 @@ final class ImageGenerator {
             addWarning("Failed to compress image", destination: destination, path: destination)
         }
     }
+
+    private func optimizeImages() {
+        let all = generatedImages
+            .filter { imageOptimSupportedFileExtensions.contains($0.lastComponentAfter(".")) }
+            .map { output.appendingPathComponent($0).path }
+        for i in stride(from: 0, to: all.count, by: imageOptimizationBatchSize) {
+            let endIndex = min(i+imageOptimizationBatchSize, all.count)
+            let batch = all[i..<endIndex]
+            print(String(format: "Optimizing images: %4d / %d\r", endIndex, all.count), terminator: "")
+            fflush(stdout)
+            if optimizeImageBatch(batch) {
+                optimizedImages.formUnion(batch)
+            }
+        }
+        print("                                     \r", terminator: "")
+        fflush(stdout)
+        print("\(optimizedImages.count) images optimized")
+    }
+
+    private func optimizeImageBatch(_ batch: ArraySlice<String>) -> Bool {
+        let command = "imageoptim " + batch.joined(separator: " ")
+        do {
+            _ = try FileSystem.safeShell(command)
+            return true
+        } catch {
+            addWarning("Failed to optimize images", destination: "", path: "")
+            return false
+        }
+    }
 }