update tests and resizing algorithm

packages/image_picker/image_picker_for_web/example/integration_test/image_resizer_test.dart

@@ -29,6 +29,39 @@ void main() {
         name: pngHtmlFile.name, mimeType: pngHtmlFile.type);
   });
 
+  testWidgets("image is loaded correctly ", (WidgetTester tester) async {
+    final imageElement = await imageResizer.loadImage(pngFile.path);
+    expect(imageElement.width!, 10);
+    expect(imageElement.height!, 10);
+  });
+
+  testWidgets(
+      "canvas is loaded with image's width and height when max width and max height are null",
+      (widgetTester) async {
+    final imageElement = await imageResizer.loadImage(pngFile.path);
+    final canvas = imageResizer.resizeImageElement(imageElement, null, null);
+    expect(canvas.width, imageElement.width);
+    expect(canvas.height, imageElement.height);
+  });
+
+  testWidgets(
+      "canvas size is scaled when max width and max height are not null",
+      (widgetTester) async {
+    final imageElement = await imageResizer.loadImage(pngFile.path);
+    final canvas = imageResizer.resizeImageElement(imageElement, 8, 8);
+    expect(canvas.width, 8);
+    expect(canvas.height, 8);
+  });
+
+  testWidgets("resized image is returned after converting canvas to file",
+      (widgetTester) async {
+    final imageElement = await imageResizer.loadImage(pngFile.path);
+    final canvas = imageResizer.resizeImageElement(imageElement, null, null);
+    final resizedImage =
+        await imageResizer.writeCanvasToFile(pngFile, canvas, null);
+    expect(resizedImage.name, "scaled_${pngFile.name}");
+  });
+
   testWidgets("image is scaled when maxWidth is set",
       (WidgetTester tester) async {
     final scaledImage =
@@ -37,6 +70,7 @@ void main() {
     final scaledImageSize = await _getImageSize(scaledImage);
     expect(scaledImageSize, Size(5, 5));
   });
+
   testWidgets("image is scaled when maxHeight is set",
       (WidgetTester tester) async {
     final scaledImage =

packages/image_picker/image_picker_for_web/lib/image_resizer_utils.dart

@@ -5,6 +5,8 @@
 import 'dart:math';
 import 'dart:ui';
 
+import 'package:flutter/material.dart';
+
 ///a function that checks if an image needs to be resized or not
 bool imageResizeNeeded(double? maxWidth, double? maxHeight, int? imageQuality) {
   return imageQuality != null
@@ -24,41 +26,8 @@ bool isImageQualityValid(int imageQuality) {
 /// maxHeight is the maximum height of the scaled image
 Size calculateSizeOfDownScaledImage(
     Size imageSize, double? maxWidth, double? maxHeight) {
-  double originalWidth = imageSize.width;
-  double originalHeight = imageSize.height;
-
-  bool hasMaxWidth = maxWidth != null;
-  bool hasMaxHeight = maxHeight != null;
-  double width = hasMaxWidth ? min(maxWidth, originalWidth) : originalWidth;
-  double height =
-      hasMaxHeight ? min(maxHeight, originalHeight) : originalHeight;
-  bool shouldDownscaleWidth = hasMaxWidth && maxWidth < originalWidth;
-  bool shouldDownscaleHeight = hasMaxHeight && maxHeight < originalHeight;
-  bool shouldDownscale = shouldDownscaleWidth || shouldDownscaleHeight;
-  if (shouldDownscale) {
-    double downscaledWidth =
-        ((height / originalHeight) * originalWidth).floorToDouble();
-    double downscaledHeight =
-        ((width / originalWidth) * originalHeight).floorToDouble();
-    if (width < height) {
-      if (!hasMaxWidth) {
-        width = downscaledWidth;
-      } else {
-        height = downscaledHeight;
-      }
-    } else if (height < width) {
-      if (!hasMaxHeight) {
-        height = downscaledHeight;
-      } else {
-        width = downscaledWidth;
-      }
-    } else {
-      if (originalWidth < originalHeight) {
-        width = downscaledWidth;
-      } else if (originalHeight < originalWidth) {
-        height = downscaledHeight;
-      }
-    }
-  }
-  return Size(width, height);
+  double widthFactor = maxWidth != null ? imageSize.width / maxWidth : 1;
+  double heightFactor = maxHeight != null ? imageSize.height / maxHeight : 1;
+  double resizeFactor = max(widthFactor, heightFactor);
+  return (resizeFactor > 1 ? imageSize ~/ resizeFactor : imageSize);
 }