[image_picker_for_web] Added support for maxWidth, maxHeight and imageQuality

packages/image_picker/image_picker_for_web/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 2.1.4
+
+* Implemented `maxWidth`, `maxHeight` and `imageQuality` when selecting images
+  (except for gifs).
+
 ## 2.1.3
 
 * Add `implements` to pubspec.

packages/image_picker/image_picker_for_web/README.md

@@ -43,7 +43,8 @@ Each browser may implement `capture` any way they please, so it may (or may not)
 difference in your users' experience.
 
 ### pickImage()
-The arguments `maxWidth`, `maxHeight` and `imageQuality` are not supported on the web.
+The arguments `maxWidth`, `maxHeight` and `imageQuality` are not supported for gif images.
+The argument `imageQuality` only works for jpeg and webp images.
 
 ### pickVideo()
 The argument `maxDuration` is not supported on the web.
@@ -63,7 +64,7 @@ You should be able to use `package:image_picker` _almost_ as normal.
 Once the user has picked a file, the returned `PickedFile` instance will contain a
 `network`-accessible URL (pointing to a location within the browser).
 
-The instace will also let you retrieve the bytes of the selected file across all platforms.
+The instance will also let you retrieve the bytes of the selected file across all platforms.
 
 If you want to use the path directly, your code would need look like this:
 

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

@@ -0,0 +1,128 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:html' as html;
+import 'dart:typed_data';
+import 'dart:ui';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:image_picker_for_web/src/image_resizer.dart';
+import 'package:image_picker_platform_interface/image_picker_platform_interface.dart';
+import 'package:integration_test/integration_test.dart';
+
+//This is a sample 10x10 png image
+final String pngFileBase64Contents =
+    "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKAQMAAAC3/F3+AAAABGdBTUEAALGPC/xhBQAAACBjSFJNAAB6JgAAgIQAAPoAAACA6AAAdTAAAOpgAAA6mAAAF3CculE8AAAABlBMVEXqQzX+/v6lfubTAAAAAWJLR0QB/wIt3gAAAAlwSFlzAAAHEwAABxMBziAPCAAAAAd0SU1FB+UJHgsdDM0ErZoAAAALSURBVAjXY2DABwAAHgABboVHMgAAACV0RVh0ZGF0ZTpjcmVhdGUAMjAyMS0wOS0zMFQxMToyOToxMi0wNDowMHCDC24AAAAldEVYdGRhdGU6bW9kaWZ5ADIwMjEtMDktMzBUMTE6Mjk6MTItMDQ6MDAB3rPSAAAAAElFTkSuQmCC";
+
+void main() {
+  IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+
+  // Under test...
+  late ImageResizer imageResizer;
+  late XFile pngFile;
+  setUp(() {
+    imageResizer = ImageResizer();
+    final pngHtmlFile = _base64ToFile(pngFileBase64Contents, "pngImage.png");
+    pngFile = XFile(html.Url.createObjectUrl(pngHtmlFile),
+        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_${pngFile.name}");
+  });
+
+  testWidgets("image is scaled when maxWidth is set",
+      (WidgetTester tester) async {
+    final scaledImage =
+        await imageResizer.resizeImageIfNeeded(pngFile, 5, null, null);
+    expect(scaledImage.name, "scaled_${pngFile.name}");
+    final scaledImageSize = await _getImageSize(scaledImage);
+    expect(scaledImageSize, Size(5, 5));
+  });
+
+  testWidgets("image is scaled when maxHeight is set",
+      (WidgetTester tester) async {
+    final scaledImage =
+        await imageResizer.resizeImageIfNeeded(pngFile, null, 6, null);
+    expect(scaledImage.name, "scaled_${pngFile.name}");
+    final scaledImageSize = await _getImageSize(scaledImage);
+    expect(scaledImageSize, Size(6, 6));
+  });
+
+  testWidgets("image is scaled when imageQuality is set",
+      (WidgetTester tester) async {
+    final scaledImage =
+        await imageResizer.resizeImageIfNeeded(pngFile, null, null, 89);
+    expect(scaledImage.name, "scaled_${pngFile.name}");
+  });
+
+  testWidgets("image is scaled when maxWidth,maxHeight,imageQuality are set",
+      (WidgetTester tester) async {
+    final scaledImage =
+        await imageResizer.resizeImageIfNeeded(pngFile, 3, 4, 89);
+    expect(scaledImage.name, "scaled_${pngFile.name}");
+  });
+
+  testWidgets("image is not scaled when maxWidth,maxHeight, is set",
+      (WidgetTester tester) async {
+    final scaledImage =
+        await imageResizer.resizeImageIfNeeded(pngFile, null, null, null);
+    expect(scaledImage.name, pngFile.name);
+  });
+}
+
+Future<Size> _getImageSize(XFile file) async {
+  final completer = Completer<Size>();
+  final image = html.ImageElement(src: file.path);
+  image.onLoad.listen((event) {
+    completer.complete(Size(image.width!.toDouble(), image.height!.toDouble()));
+  });
+  image.onError.listen((event) {
+    completer.complete(Size(0, 0));
+  });
+  return completer.future;
+}
+
+html.File _base64ToFile(String data, String fileName) {
+  var arr = data.split(',');
+  var bstr = html.window.atob(arr[1]);
+  var n = bstr.length, u8arr = Uint8List(n);
+
+  while (n >= 1) {
+    u8arr[n - 1] = bstr.codeUnitAt(n - 1);
+    n--;
+  }
+
+  return html.File([u8arr], fileName);
+}

packages/image_picker/image_picker_for_web/lib/image_picker_for_web.dart

@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:html' as html;
 
 import 'package:flutter_web_plugins/flutter_web_plugins.dart';
+import 'package:image_picker_for_web/src/image_resizer.dart';
 import 'package:meta/meta.dart';
 import 'package:image_picker_platform_interface/image_picker_platform_interface.dart';
 
@@ -23,10 +24,14 @@ class ImagePickerPlugin extends ImagePickerPlatform {
 
   late html.Element _target;
 
+  late ImageResizer _imageResizer;
+
   /// A constructor that allows tests to override the function that creates file inputs.
   ImagePickerPlugin({
     @visibleForTesting ImagePickerPluginTestOverrides? overrides,
+    @visibleForTesting ImageResizer? imageResizer,
   }) : _overrides = overrides {
+    _imageResizer = imageResizer ?? ImageResizer();
     _target = _ensureInitialized(_kImagePickerInputsDomId);
   }
 
@@ -122,7 +127,12 @@ class ImagePickerPlugin extends ImagePickerPlatform {
       accept: _kAcceptImageMimeType,
       capture: capture,
     );
-    return files.first;
+    return _imageResizer.resizeImageIfNeeded(
+      files.first,
+      maxWidth,
+      maxHeight,
+      imageQuality,
+    );
   }
 
   /// Returns an [XFile] containing the video that was picked.
@@ -157,8 +167,21 @@ class ImagePickerPlugin extends ImagePickerPlatform {
     double? maxWidth,
     double? maxHeight,
     int? imageQuality,
-  }) {
-    return getFiles(accept: _kAcceptImageMimeType, multiple: true);
+  }) async {
+    final List<XFile> images = await getFiles(
+      accept: _kAcceptImageMimeType,
+      multiple: true,
+    );
+    final Iterable<Future<XFile>> resized = images.map(
+      (image) => _imageResizer.resizeImageIfNeeded(
+        image,
+        maxWidth,
+        maxHeight,
+        imageQuality,
+      ),
+    );
+
+    return Future.wait<XFile>(resized);
   }
 
   /// Injects a file input with the specified accept+capture attributes, and
@@ -244,17 +267,17 @@ class ImagePickerPlugin extends ImagePickerPlatform {
     input.onChange.first.then((event) {
       final files = _handleOnChangeEvent(event);
       if (!_completer.isCompleted && files != null) {
-        _completer.complete(files
-            .map((file) => XFile(
-                  html.Url.createObjectUrl(file),
-                  name: file.name,
-                  length: file.size,
-                  lastModified: DateTime.fromMillisecondsSinceEpoch(
-                    file.lastModified ?? DateTime.now().millisecondsSinceEpoch,
-                  ),
-                  mimeType: file.type,
-                ))
-            .toList());
+        _completer.complete(files.map((file) {
+          return XFile(
+            html.Url.createObjectUrl(file),
+            name: file.name,
+            length: file.size,
+            lastModified: DateTime.fromMillisecondsSinceEpoch(
+              file.lastModified ?? DateTime.now().millisecondsSinceEpoch,
+            ),
+            mimeType: file.type,
+          );
+        }).toList());
       }
     });
     input.onError.first.then((event) {

packages/image_picker/image_picker_for_web/lib/src/image_resizer.dart

@@ -0,0 +1,83 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:math';
+import 'dart:ui';
+import 'package:image_picker_for_web/src/image_resizer_utils.dart';
+import 'package:image_picker_platform_interface/image_picker_platform_interface.dart';
+import 'dart:html' as html;
+
+/// Helper class that resizes images.
+class ImageResizer {
+  /// Resizes the image if needed.
+  /// (Does not support gif images)
+  Future<XFile> resizeImageIfNeeded(XFile file, double? maxWidth,
+      double? maxHeight, int? imageQuality) async {
+    if (!imageResizeNeeded(maxWidth, maxHeight, imageQuality) ||
+        file.mimeType == "image/gif") {
+      // Implement maxWidth and maxHeight for image/gif
+      return file;
+    }
+    try {
+      final imageElement = await loadImage(file.path);
+      final canvas = resizeImageElement(imageElement, maxWidth, maxHeight);
+      final resizedImage = await writeCanvasToFile(file, canvas, imageQuality);
+      html.Url.revokeObjectUrl(file.path);
+      return resizedImage;
+    } catch (e) {
+      return file;
+    }
+  }
+
+  /// function that loads the blobUrl into an imageElement
+  Future<html.ImageElement> loadImage(String blobUrl) {
+    final imageLoadCompleter = Completer<html.ImageElement>();
+    final imageElement = html.ImageElement();
+    imageElement.src = blobUrl;
+
+    imageElement.onLoad.listen((event) {
+      imageLoadCompleter.complete(imageElement);
+    });
+    imageElement.onError.listen((event) {
+      final exception = ("Error while loading image.");
+      imageElement.remove();
+      imageLoadCompleter.completeError(exception);
+    });
+    return imageLoadCompleter.future;
+  }
+
+  /// Draws image to a canvas while resizing the image to fit the [maxWidth],[maxHeight] constraints
+  html.CanvasElement resizeImageElement(
+      html.ImageElement source, double? maxWidth, double? maxHeight) {
+    final newImageSize = calculateSizeOfDownScaledImage(
+        Size(source.width!.toDouble(), source.height!.toDouble()),
+        maxWidth,
+        maxHeight);
+    final canvas = html.CanvasElement();
+    canvas.width = newImageSize.width.toInt();
+    canvas.height = newImageSize.height.toInt();
+    final context = canvas.context2D;
+    if (maxHeight == null && maxWidth == null) {
+      context.drawImage(source, 0, 0);
+    } else {
+      context.drawImageScaled(source, 0, 0, canvas.width!, canvas.height!);
+    }
+    return canvas;
+  }
+
+  /// function that converts a canvas element to Xfile
+  /// [imageQuality] is only supported for jpeg and webp images.
+  Future<XFile> writeCanvasToFile(
+      XFile originalFile, html.CanvasElement canvas, int? imageQuality) async {
+    final calculatedImageQuality = ((min(imageQuality ?? 100, 100)) / 100.0);
+    final blob =
+        await canvas.toBlob(originalFile.mimeType, calculatedImageQuality);
+    return XFile(html.Url.createObjectUrlFromBlob(blob),
+        mimeType: originalFile.mimeType,
+        name: "scaled_" + originalFile.name,
+        lastModified: DateTime.now(),
+        length: blob.size);
+  }
+}

packages/image_picker/image_picker_for_web/lib/src/image_resizer_utils.dart

@@ -0,0 +1,33 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+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
+      ? isImageQualityValid(imageQuality)
+      : (maxWidth != null || maxHeight != null);
+}
+
+/// a function that checks if image quality is between 0 to 100
+bool isImageQualityValid(int imageQuality) {
+  return (imageQuality >= 0 && imageQuality <= 100);
+}
+
+/// a function that calculates the size of the downScaled image.
+/// imageWidth is the width of the image
+/// imageHeight is the height of  the image
+/// maxWidth is the maximum width of the scaled image
+/// maxHeight is the maximum height of the scaled image
+Size calculateSizeOfDownScaledImage(
+    Size imageSize, double? maxWidth, double? maxHeight) {
+  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);
+}

packages/image_picker/image_picker_for_web/pubspec.yaml

@@ -2,7 +2,7 @@ name: image_picker_for_web
 description: Web platform implementation of image_picker
 repository: https://github.com/flutter/plugins/tree/master/packages/image_picker/image_picker_for_web
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+image_picker%22
-version: 2.1.3
+version: 2.1.4
 
 environment:
   sdk: ">=2.12.0 <3.0.0"