fix: nullable

README.md

@@ -47,11 +47,11 @@ final jpegData = await ImageConverter.convert(
   quality: 90,
 );
 
-// Convert and resize an image to fit within 200x200
+// Convert and resize an image to fit within a width of 200, scaling height proportionally
 final resizedData = await ImageConverter.convert(
   inputData: imageData,
   format: OutputFormat.png,
-  resizeMode: const FitResizeMode(width: 200, height: 200),
+  resizeMode: const FitResizeMode(width: 200),
 );
 
 // Convert any format to PNG
@@ -117,7 +117,7 @@ A sealed class representing different ways to resize an image.
 
 - **`OriginalResizeMode()`**: Keeps the original dimensions of the image.
 - **`ExactResizeMode({required int width, required int height})`**: Resizes the image to exact dimensions, possibly changing the aspect ratio.
-- **`FitResizeMode({required int width, required int height})`**: Fits the image within the specified dimensions while maintaining the aspect ratio. If the image is smaller than the specified dimensions, it will not be scaled up.
+- **`FitResizeMode({int? width, int? height})`**: Fits the image within the specified dimensions while maintaining the aspect ratio. At least one of `width` or `height` must be provided. If only one dimension is provided, the other is scaled proportionally. If the image is smaller than the specified dimensions, it will not be scaled up.
 
 
 ## Implementation Details

example/integration_test/app_test.dart

@@ -90,6 +90,42 @@ void main() {
       expect(resizedImage.width, equals(originalWidth));
       expect(resizedImage.height, equals(originalHeight));
     });
+
+    test('FitResizeMode with only width maintains aspect ratio', () async {
+      // Original jpeg.jpg is 1502x2000
+      final targetWidth = 150;
+      final expectedWidth = 150;
+      final expectedHeight = 200;
+
+      final converted = await ImageConverter.convert(
+        inputData: jpegData,
+        format: OutputFormat.jpeg,
+        resizeMode: FitResizeMode(width: targetWidth),
+      );
+
+      final resizedImage = img.decodeImage(converted)!;
+      // Allow for small rounding differences
+      expect(resizedImage.width, closeTo(expectedWidth, 1));
+      expect(resizedImage.height, closeTo(expectedHeight, 1));
+    });
+
+    test('FitResizeMode with only height maintains aspect ratio', () async {
+      // Original jpeg.jpg is 1502x2000
+      final targetHeight = 200;
+      final expectedWidth = 150;
+      final expectedHeight = 200;
+
+      final converted = await ImageConverter.convert(
+        inputData: jpegData,
+        format: OutputFormat.jpeg,
+        resizeMode: FitResizeMode(height: targetHeight),
+      );
+
+      final resizedImage = img.decodeImage(converted)!;
+      // Allow for small rounding differences
+      expect(resizedImage.width, closeTo(expectedWidth, 1));
+      expect(resizedImage.height, closeTo(expectedHeight, 1));
+    });
   });
 
   group('File size consistency tests', () {

example/lib/main.dart

@@ -70,8 +70,8 @@ class _MainPageState extends State<MainPage> {
       final resizeMode = switch ((width, height)) {
         (null, null) => const OriginalResizeMode(),
         (final w?, final h?) => ExactResizeMode(width: w, height: h),
-        (final w?, null) => FitResizeMode(width: w, height: 1 << 30),
+        (final w?, null) => FitResizeMode(width: w),
-        (null, final h?) => FitResizeMode(width: 1 << 30, height: h),
+        (null, final h?) => FitResizeMode(height: h),
       };
 
       final converted = await ImageConverter.convert(

lib/src/android/native.dart

@@ -72,26 +72,51 @@ final class ImageConverterAndroid implements ImageConverterPlatform {
           final originalWidth = originalBitmap.getWidth();
           final originalHeight = originalBitmap.getHeight();
 
-          if (originalWidth <= width && originalHeight <= height) {
+          double newWidth;
-            bitmapToCompress = originalBitmap;
+          double newHeight;
-          } else {
-            final aspectRatio = originalWidth / originalHeight;
-            var newWidth = width.toDouble();
-            var newHeight = newWidth / aspectRatio;
 
+          if (width != null && height != null) {
+            if (originalWidth <= width && originalHeight <= height) {
+              bitmapToCompress = originalBitmap;
+              break;
+            }
+            final aspectRatio = originalWidth / originalHeight;
+            newWidth = width.toDouble();
+            newHeight = newWidth / aspectRatio;
             if (newHeight > height) {
               newHeight = height.toDouble();
               newWidth = newHeight * aspectRatio;
             }
-
+          } else if (width != null) {
-            scaledBitmap = Bitmap.createScaledBitmap(
+            if (originalWidth <= width) {
-              originalBitmap,
+              bitmapToCompress = originalBitmap;
-              newWidth.round(),
+              break;
-              newHeight.round(),
+            }
-              true, // filter
+            newWidth = width.toDouble();
-            );
+            final aspectRatio = originalWidth / originalHeight;
-            bitmapToCompress = scaledBitmap;
+            newHeight = newWidth / aspectRatio;
+          } else if (height != null) {
+            if (originalHeight <= height) {
+              bitmapToCompress = originalBitmap;
+              break;
+            }
+            newHeight = height.toDouble();
+            final aspectRatio = originalWidth / originalHeight;
+            newWidth = newHeight * aspectRatio;
+          } else {
+            // This case should not be reachable due to the assertion
+            // in the FitResizeMode constructor.
+            bitmapToCompress = originalBitmap;
+            break;
           }
+
+          scaledBitmap = Bitmap.createScaledBitmap(
+            originalBitmap,
+            newWidth.round(),
+            newHeight.round(),
+            true, // filter
+          );
+          bitmapToCompress = scaledBitmap;
       }
 
       if (bitmapToCompress == null) {

lib/src/darwin/native.dart

@@ -82,23 +82,48 @@ final class ImageConverterDarwin implements ImageConverterPlatform {
           final originalWidth = CGImageGetWidth(originalImage);
           final originalHeight = CGImageGetHeight(originalImage);
 
-          if (originalWidth <= width && originalHeight <= height) {
+          double newWidth;
-            imageToEncode = originalImage;
+          double newHeight;
-          } else {
-            final aspectRatio = originalWidth / originalHeight;
-            var newWidth = width.toDouble();
-            var newHeight = newWidth / aspectRatio;
 
+          if (width != null && height != null) {
+            if (originalWidth <= width && originalHeight <= height) {
+              imageToEncode = originalImage;
+              break;
+            }
+            final aspectRatio = originalWidth / originalHeight;
+            newWidth = width.toDouble();
+            newHeight = newWidth / aspectRatio;
             if (newHeight > height) {
               newHeight = height.toDouble();
               newWidth = newHeight * aspectRatio;
             }
-            imageToEncode = _resizeImage(
+          } else if (width != null) {
-              originalImage,
+            if (originalWidth <= width) {
-              newWidth.round(),
+              imageToEncode = originalImage;
-              newHeight.round(),
+              break;
-            );
+            }
+            newWidth = width.toDouble();
+            final aspectRatio = originalWidth / originalHeight;
+            newHeight = newWidth / aspectRatio;
+          } else if (height != null) {
+            if (originalHeight <= height) {
+              imageToEncode = originalImage;
+              break;
+            }
+            newHeight = height.toDouble();
+            final aspectRatio = originalWidth / originalHeight;
+            newWidth = newHeight * aspectRatio;
+          } else {
+            // This case should not be reachable due to the assertion
+            // in the FitResizeMode constructor.
+            imageToEncode = originalImage;
+            break;
           }
+          imageToEncode = _resizeImage(
+            originalImage,
+            newWidth.round(),
+            newHeight.round(),
+          );
       }
       if (imageToEncode == nullptr) {
         throw Exception('Failed to prepare image for encoding.');

lib/src/output_resize.dart

@@ -26,11 +26,12 @@ class ExactResizeMode extends ResizeMode {
 /// If the image is smaller than the specified dimensions, it will not be
 /// scaled up.
 class FitResizeMode extends ResizeMode {
-  const FitResizeMode({required this.width, required this.height});
+  const FitResizeMode({this.width, this.height})
+    : assert(width != null || height != null);
 
   /// The maximum width for the resized image.
-  final int width;
+  final int? width;
 
   /// The maximum height for the resized image.
-  final int height;
+  final int? height;
 }

lib/src/web/web.dart

@@ -70,21 +70,53 @@ final class ImageConverterWeb implements ImageConverterPlatform {
         destWidth = w;
         destHeight = h;
       case FitResizeMode(:final width, :final height):
-        if (img.width <= width && img.height <= height) {
+        final originalWidth = img.width;
-          destWidth = img.width;
+        final originalHeight = img.height;
-          destHeight = img.height;
-        } else {
-          final aspectRatio = img.width / img.height;
-          var newWidth = width.toDouble();
-          var newHeight = newWidth / aspectRatio;
 
+        double newWidth;
+        double newHeight;
+
+        if (width != null && height != null) {
+          if (originalWidth <= width && originalHeight <= height) {
+            destWidth = originalWidth;
+            destHeight = originalHeight;
+            break;
+          }
+          final aspectRatio = originalWidth / originalHeight;
+          newWidth = width.toDouble();
+          newHeight = newWidth / aspectRatio;
           if (newHeight > height) {
             newHeight = height.toDouble();
             newWidth = newHeight * aspectRatio;
           }
-          destWidth = newWidth.round();
+        } else if (width != null) {
-          destHeight = newHeight.round();
+          if (originalWidth <= width) {
+            destWidth = originalWidth;
+            destHeight = originalHeight;
+            break;
+          }
+          newWidth = width.toDouble();
+          final aspectRatio = originalWidth / originalHeight;
+          newHeight = newWidth / aspectRatio;
+        } else if (height != null) {
+          if (originalHeight <= height) {
+            destWidth = originalWidth;
+            destHeight = originalHeight;
+            break;
+          }
+          newHeight = height.toDouble();
+          final aspectRatio = originalWidth / originalHeight;
+          newWidth = newHeight * aspectRatio;
+        } else {
+          // This case should not be reachable due to the assertion
+          // in the FitResizeMode constructor.
+          destWidth = originalWidth;
+          destHeight = originalHeight;
+          break;
         }
+
+        destWidth = newWidth.round();
+        destHeight = newHeight.round();
     }
 
     canvas.width = destWidth;