refactor: Resizing

lib/src/android/native.dart

@@ -57,63 +57,20 @@ final class ImageConverterAndroid implements ImageConverterPlatform {
         throw Exception('Failed to decode image. Invalid image data.');
       }
 
-      switch (resizeMode) {
-        case OriginalResizeMode():
-          bitmapToCompress = originalBitmap;
-        case ExactResizeMode(width: final w, height: final h):
-          scaledBitmap = Bitmap.createScaledBitmap(
-            originalBitmap,
-            w,
-            h,
-            true, // filter
-          );
-          bitmapToCompress = scaledBitmap;
-        case FitResizeMode(:final width, :final height):
       final originalWidth = originalBitmap.getWidth();
       final originalHeight = originalBitmap.getHeight();
+      final (newWidth, newHeight) = resizeMode.calculateSize(
+        originalWidth,
+        originalHeight,
+      );
 
-          double newWidth;
+      if (newWidth == originalWidth && newHeight == originalHeight) {
-          double newHeight;
-
-          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) {
-            if (originalWidth <= width) {
-              bitmapToCompress = originalBitmap;
-              break;
-            }
-            newWidth = width.toDouble();
-            final aspectRatio = originalWidth / originalHeight;
-            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(),
+          newWidth,
-            newHeight.round(),
+          newHeight,
           true, // filter
         );
         bitmapToCompress = scaledBitmap;

lib/src/darwin/native.dart

@@ -73,58 +73,19 @@ final class ImageConverterDarwin implements ImageConverterPlatform {
         throw Exception('Failed to decode image.');
       }
 
-      switch (resizeMode) {
-        case OriginalResizeMode():
-          imageToEncode = originalImage;
-        case ExactResizeMode(width: final w, height: final h):
-          imageToEncode = _resizeImage(originalImage, w, h);
-        case FitResizeMode(:final width, :final height):
       final originalWidth = CGImageGetWidth(originalImage);
       final originalHeight = CGImageGetHeight(originalImage);
-
+      final (newWidth, newHeight) = resizeMode.calculateSize(
-          double newWidth;
+        originalWidth,
-          double newHeight;
+        originalHeight,
-
-          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;
-            }
-          } else if (width != null) {
-            if (originalWidth <= width) {
-              imageToEncode = originalImage;
-              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 (newWidth == originalWidth && newHeight == originalHeight) {
+        imageToEncode = originalImage;
+      } else {
+        imageToEncode = _resizeImage(originalImage, newWidth, newHeight);
       }
+
       if (imageToEncode == nullptr) {
         throw Exception('Failed to prepare image for encoding.');
       }

lib/src/output_resize.dart

@@ -1,11 +1,21 @@
+import 'dart:math';
+
 /// A sealed class representing different ways to resize an image.
 sealed class ResizeMode {
   const ResizeMode();
+
+  /// Calculates the target size for the image based on the original dimensions.
+  (int, int) calculateSize(int originalWidth, int originalHeight);
 }
 
 /// A resize mode that keeps the original dimensions of the image.
 class OriginalResizeMode extends ResizeMode {
   const OriginalResizeMode();
+
+  @override
+  (int, int) calculateSize(int originalWidth, int originalHeight) {
+    return (originalWidth, originalHeight);
+  }
 }
 
 /// A resize mode that resizes the image to exact dimensions,
@@ -18,6 +28,11 @@ class ExactResizeMode extends ResizeMode {
 
   /// The target height for the resized image.
   final int height;
+
+  @override
+  (int, int) calculateSize(int originalWidth, int originalHeight) {
+    return (width, height);
+  }
 }
 
 /// A resize mode that fits the image within the specified dimensions while
@@ -34,4 +49,24 @@ class FitResizeMode extends ResizeMode {
 
   /// The maximum height for the resized image.
   final int? height;
+
+  @override
+  (int, int) calculateSize(int originalWidth, int originalHeight) {
+    double scale = 1.0;
+    if (width != null && height != null) {
+      final widthScale = width! / originalWidth;
+      final heightScale = height! / originalHeight;
+      scale = min(widthScale, heightScale);
+    } else if (width != null) {
+      scale = width! / originalWidth;
+    } else if (height != null) {
+      scale = height! / originalHeight;
+    }
+
+    if (scale >= 1.0) {
+      return (originalWidth, originalHeight);
+    }
+
+    return ((originalWidth * scale).round(), (originalHeight * scale).round());
+  }
 }

lib/src/web/web.dart

@@ -59,65 +59,10 @@ final class ImageConverterWeb implements ImageConverterPlatform {
 
     final canvas = HTMLCanvasElement();
 
-    final int destWidth;
+    final (destWidth, destHeight) = resizeMode.calculateSize(
-    final int destHeight;
+      img.width,
-
+      img.height,
-    switch (resizeMode) {
+    );
-      case OriginalResizeMode():
-        destWidth = img.width;
-        destHeight = img.height;
-      case ExactResizeMode(width: final w, height: final h):
-        destWidth = w;
-        destHeight = h;
-      case FitResizeMode(:final width, :final height):
-        final originalWidth = img.width;
-        final originalHeight = img.height;
-
-        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;
-          }
-        } else if (width != null) {
-          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;
     canvas.height = destHeight;

test/output_resize_test.dart

@@ -0,0 +1,97 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:platform_image_converter/src/output_resize.dart';
+
+void main() {
+  group('ResizeMode', () {
+    const originalWidth = 1000;
+    const originalHeight = 500;
+
+    group('OriginalResizeMode', () {
+      test('should return original dimensions', () {
+        const resizeMode = OriginalResizeMode();
+        final (width, height) = resizeMode.calculateSize(
+          originalWidth,
+          originalHeight,
+        );
+        expect(width, originalWidth);
+        expect(height, originalHeight);
+      });
+    });
+
+    group('ExactResizeMode', () {
+      test('should return exact dimensions', () {
+        const resizeMode = ExactResizeMode(width: 300, height: 200);
+        final (width, height) = resizeMode.calculateSize(
+          originalWidth,
+          originalHeight,
+        );
+        expect(width, 300);
+        expect(height, 200);
+      });
+    });
+
+    group('FitResizeMode', () {
+      test('downscales with both width and height, respecting aspect ratio', () {
+        // Aspect ratio is 2:1 (1000x500)
+        // Target is 500x500, so scale should be based on width (min(500/1000, 500/500) = 0.5)
+        const resizeMode = FitResizeMode(width: 500, height: 500);
+        final (width, height) = resizeMode.calculateSize(
+          originalWidth,
+          originalHeight,
+        );
+        expect(width, 500); // 1000 * 0.5
+        expect(height, 250); // 500 * 0.5
+      });
+
+      test('does not upscale if image is smaller than target dimensions', () {
+        const resizeMode = FitResizeMode(width: 2000, height: 1000);
+        final (width, height) = resizeMode.calculateSize(
+          originalWidth,
+          originalHeight,
+        );
+        expect(width, originalWidth);
+        expect(height, originalHeight);
+      });
+
+      test('downscales with only width, respecting aspect ratio', () {
+        const resizeMode = FitResizeMode(width: 500);
+        final (width, height) = resizeMode.calculateSize(
+          originalWidth,
+          originalHeight,
+        );
+        expect(width, 500); // 1000 * 0.5
+        expect(height, 250); // 500 * 0.5
+      });
+
+      test('does not upscale with only width', () {
+        const resizeMode = FitResizeMode(width: 2000);
+        final (width, height) = resizeMode.calculateSize(
+          originalWidth,
+          originalHeight,
+        );
+        expect(width, originalWidth);
+        expect(height, originalHeight);
+      });
+
+      test('downscales with only height, respecting aspect ratio', () {
+        const resizeMode = FitResizeMode(height: 250);
+        final (width, height) = resizeMode.calculateSize(
+          originalWidth,
+          originalHeight,
+        );
+        expect(width, 500); // 1000 * 0.5
+        expect(height, 250); // 500 * 0.5
+      });
+
+      test('does not upscale with only height', () {
+        const resizeMode = FitResizeMode(height: 1000);
+        final (width, height) = resizeMode.calculateSize(
+          originalWidth,
+          originalHeight,
+        );
+        expect(width, originalWidth);
+        expect(height, originalHeight);
+      });
+    });
+  });
+}