Add parameter of image bytes before decoding

cached_network_image/lib/src/cached_image_widget.dart

@@ -195,6 +195,8 @@ class CachedNetworkImage extends StatelessWidget {
   /// Will resize the image and store the resized image in the disk cache.
   final int? maxHeightDiskCache;
 
+  final ImageBytesBeforeDecoding? beforeDecoding;
+
   /// CachedNetworkImage shows a network image using a caching mechanism. It also
   /// provides support for a placeholder, showing an error and fading into the
   /// loaded image. Next to that it supports most features of a default Image
@@ -230,6 +232,7 @@ class CachedNetworkImage extends StatelessWidget {
     this.maxHeightDiskCache,
     ImageRenderMethodForWeb imageRenderMethodForWeb =
         ImageRenderMethodForWeb.HtmlImage,
+    this.beforeDecoding,
   })  : _image = CachedNetworkImageProvider(
           imageUrl,
           headers: httpHeaders,
@@ -238,6 +241,7 @@ class CachedNetworkImage extends StatelessWidget {
           imageRenderMethodForWeb: imageRenderMethodForWeb,
           maxWidth: maxWidthDiskCache,
           maxHeight: maxHeightDiskCache,
+          beforeDecoding: beforeDecoding,
         ),
         super(key: key);
 

cached_network_image/lib/src/image_provider/_image_loader.dart

@@ -10,7 +10,7 @@ import 'package:cached_network_image_platform_interface'
     show ImageLoader;
 import 'package:cached_network_image_platform_interface'
         '/cached_network_image_platform_interface.dart'
-    show ImageRenderMethodForWeb;
+    show ImageRenderMethodForWeb, ImageBytesBeforeDecoding;
 
 /// ImageLoader class to load images on IO platforms.
 class ImageLoader implements platform.ImageLoader {
@@ -27,6 +27,7 @@ class ImageLoader implements platform.ImageLoader {
     Function()? errorListener,
     ImageRenderMethodForWeb imageRenderMethodForWeb,
     Function() evictImage,
+    ImageBytesBeforeDecoding? beforeDecoding,
   ) async* {
     try {
       assert(
@@ -56,6 +57,9 @@ class ImageLoader implements platform.ImageLoader {
         if (result is FileInfo) {
           var file = result.file;
           var bytes = await file.readAsBytes();
+          if (beforeDecoding != null) {
+            bytes = await beforeDecoding(bytes, url);
+          }
           var decoded = await decode(bytes);
           yield decoded;
         }

cached_network_image/lib/src/image_provider/cached_network_image_provider.dart

@@ -2,7 +2,7 @@ import 'dart:async' show Future, StreamController;
 import 'dart:ui' as ui show Codec;
 
 import 'package:cached_network_image_platform_interface/cached_network_image_platform_interface.dart'
-    show ImageRenderMethodForWeb;
+    show ImageBytesBeforeDecoding, ImageRenderMethodForWeb;
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_cache_manager/flutter_cache_manager.dart';
@@ -34,6 +34,7 @@ class CachedNetworkImageProvider
     this.cacheManager,
     this.cacheKey,
     this.imageRenderMethodForWeb = ImageRenderMethodForWeb.HtmlImage,
+    this.beforeDecoding,
   });
 
   /// CacheManager from which the image files are loaded.
@@ -65,6 +66,8 @@ class CachedNetworkImageProvider
   /// Render option for images on the web platform.
   final ImageRenderMethodForWeb imageRenderMethodForWeb;
 
+  final ImageBytesBeforeDecoding? beforeDecoding;
+
   @override
   Future<CachedNetworkImageProvider> obtainKey(
       ImageConfiguration configuration) {
@@ -107,6 +110,7 @@ class CachedNetworkImageProvider
       errorListener,
       imageRenderMethodForWeb,
       () => PaintingBinding.instance?.imageCache?.evict(key),
+      beforeDecoding,
     );
   }
 

cached_network_image/pubspec.yaml

@@ -9,8 +9,12 @@ dependencies:
     sdk: flutter
   flutter_cache_manager: ^3.0.0
   octo_image: ^1.0.0
-  cached_network_image_platform_interface: ^1.0.0
-  cached_network_image_web: ^1.0.0
+  #cached_network_image_platform_interface: ^1.0.0
+  cached_network_image_platform_interface:
+    path: ../cached_network_image_platform_interface/
+  #cached_network_image_web: ^1.0.0
+  cached_network_image_web:
+    path: ../cached_network_image_web/
 
 
 dev_dependencies:

cached_network_image_platform_interface/lib/cached_network_image_platform_interface.dart

@@ -1,6 +1,7 @@
 library cached_network_image_platform_interface;
 
 import 'dart:async';
+import 'dart:typed_data';
 import 'dart:ui' as ui;
 
 import 'package:flutter/material.dart';
@@ -17,6 +18,12 @@ enum ImageRenderMethodForWeb {
   HttpGet, // ignore: constant_identifier_names
 }
 
+///
+typedef ImageBytesBeforeDecoding = Future<Uint8List> Function(
+  Uint8List bytes,
+  String url,
+);
+
 /// ImageLoader class to load images differently on various platforms.
 class ImageLoader {
   /// loads the images async and gives the resulted codecs on a Stream. The
@@ -33,6 +40,7 @@ class ImageLoader {
     Function()? errorListener,
     ImageRenderMethodForWeb imageRenderMethodForWeb,
     Function() evictImage,
+    ImageBytesBeforeDecoding? beforeDecoding,
   ) {
     throw UnimplementedError();
   }

cached_network_image_platform_interface/test/cached_network_image_platform_interface_test.dart

@@ -26,7 +26,8 @@ void main() {
               null,
               null,
               ImageRenderMethodForWeb.HttpGet,
-              () => {}),
+              () => {},
+              null),
           throwsA(const TypeMatcher<UnimplementedError>()));
     });
   });

cached_network_image_web/lib/cached_network_image_web.dart

@@ -5,7 +5,7 @@ import 'dart:ui' as ui;
 
 import 'package:cached_network_image_platform_interface'
         '/cached_network_image_platform_interface.dart' as platform
-    show ImageLoader;
+    show ImageBytesBeforeDecoding, ImageLoader;
 import 'package:cached_network_image_platform_interface'
         '/cached_network_image_platform_interface.dart'
     show ImageRenderMethodForWeb;
@@ -27,6 +27,7 @@ class ImageLoader implements platform.ImageLoader {
     Function()? errorListener,
     ImageRenderMethodForWeb imageRenderMethodForWeb,
     Function() evictImage,
+    platform.ImageBytesBeforeDecoding? beforeDecoding,
   ) {
     switch (imageRenderMethodForWeb) {
       case ImageRenderMethodForWeb.HttpGet:
@@ -41,6 +42,7 @@ class ImageLoader implements platform.ImageLoader {
           headers,
           errorListener,
           evictImage,
+          beforeDecoding,
         );
       case ImageRenderMethodForWeb.HtmlImage:
         return _loadAsyncHtmlImage(url, chunkEvents, decode).asStream();
@@ -58,6 +60,7 @@ class ImageLoader implements platform.ImageLoader {
     Map<String, String>? headers,
     Function()? errorListener,
     Function() evictImage,
+    platform.ImageBytesBeforeDecoding? beforeDecoding,
   ) async* {
     try {
       await for (var result in cacheManager.getFileStream(url,
@@ -71,6 +74,9 @@ class ImageLoader implements platform.ImageLoader {
         if (result is FileInfo) {
           var file = result.file;
           var bytes = await file.readAsBytes();
+          if (beforeDecoding != null) {
+            bytes = await beforeDecoding(bytes, url);
+          }
           var decoded = await decode(bytes);
           yield decoded;
         }

cached_network_image_web/pubspec.yaml

@@ -11,7 +11,9 @@ dependencies:
   flutter:
     sdk: flutter
   flutter_cache_manager: ^3.0.0
-  cached_network_image_platform_interface: ^1.0.0
+  #cached_network_image_platform_interface: ^1.0.0
+  cached_network_image_platform_interface:
+    path: ../cached_network_image_platform_interface/
 
 dev_dependencies:
   flutter_test:

cached_network_image_web/test/cached_network_image_web_test.dart

@@ -24,7 +24,8 @@ void main() {
         null,
         null,
         ImageRenderMethodForWeb.HttpGet,
-        () => {});
+        () => {},
+        null);
     expect(stream, isNotNull);
   });
 }