flutter_image_compress 0.3.1 flutter_image_compress: ^0.3.1 copied to clipboard
compress image with native code(objc kotlin), it's faster. This library can work on android/ios.
flutter_image_compress #
Compresses image as native plugin (Obj-C/Kotlin)
This library can works on Android and iOS.
Why #
Q:Dart already has image compression libraries. Why use native?
A:For unknown reasons, image compression in Dart language is not efficient, even in release version. Using isolate does not solve the problem.
About params #
MinWidth and minHeight are constraints on image scaling.
For example, a 4000*2000 image, minWidth set to 1920, minHeight set to 1080, the calculation is as follows:
// Using dart as an example, the actual implementation is Kotlin or OC.
import 'dart:math' as math;
void main() {
var scale = calcScale(
srcWidth: 4000,
srcHeight: 2000,
minWidth: 1920,
minHeight: 1080,
);
print("scale = $scale"); // scale = 1.8518518518518519
print("target width = ${4000 / scale}, height = ${2000 / scale}"); // target width = 2160.0, height = 1080.0
}
double calcScale({
double srcWidth,
double srcHeight,
double minWidth,
double minHeight,
}) {
var scaleW = srcWidth / minWidth;
var scaleH = srcHeight / minHeight;
var scale = math.max(1.0, math.min(scaleW, scaleH));
return scale;
}
Android #
You may need to update Kotlin to version 1.2.71
(Recommend 1.3.21) or higher.
iOS #
No problems currently found.
Usage #
dependencies:
flutter_image_compress: ^0.2.4
import 'package:flutter_image_compress/flutter_image_compress.dart';
Use as:
Future<List<int>> testCompressFile(File file) async {
var result = await FlutterImageCompress.compressWithFile(
file.absolute.path,
minWidth: 2300,
minHeight: 1500,
quality: 94,
rotate: 90,
);
print(file.lengthSync());
print(result.length);
return result;
}
Future<File> testCompressAndGetFile(File file, String targetPath) async {
var result = await FlutterImageCompress.compressAndGetFile(
file.absolute.path, targetPath,
quality: 88,
rotate: 180,
);
print(file.lengthSync());
print(result.lengthSync());
return result;
}
Future<List<int>> testCompressAsset(String assetName) async {
var list = await FlutterImageCompress.compressAssetImage(
assetName,
minHeight: 1920,
minWidth: 1080,
quality: 96,
rotate: 180,
);
return list;
}
Future<List<int>> testComporessList(List<int> list) async {
var result = await FlutterImageCompress.compressWithList(
list,
minHeight: 1920,
minWidth: 1080,
quality: 96,
rotate: 135,
);
print(list.length);
print(result.length);
return result;
}
About List<int>
vs Uint8List
#
You may need to convert List<int>
to Uint8List
to display images.
To use Uint8List
, you need import package to your code like so:
final image = Uint8List.fromList(imageList)
ImageProvider provider = MemoryImage(Uint8List.fromList(imageList));
Usage in Image
Widget:
List<int> image = await testCompressFile(file);
ImageProvider provider = MemoryImage(Uint8List.fromList(image));
Image(
image: provider ?? AssetImage("img/img.jpg"),
),
Write to file usage:
void writeToFile(List<int> image, String filePath) {
final file = File(filePath);
file.writeAsBytes(image, flush: true, mode: FileMode.write);
}
Troubleshooting #
Compressing returns null
#
Sometimes, compressing will return null. You should check if you can read/write the file, and the parent folder of the target file must exist.
For example, use the path_provider plugin to access some application folders, and use a permission plugin to request permission to access SD cards on Android/iOS.
Android build error #
Caused by: org.gradle.internal.event.ListenerNotificationException: Failed to notify project evaluation listener.
at org.gradle.internal.event.AbstractBroadcastDispatch.dispatch(AbstractBroadcastDispatch.java:86)
...
Caused by: java.lang.AbstractMethodError
at org.jetbrains.kotlin.gradle.plugin.KotlinPluginKt.resolveSubpluginArtifacts(KotlinPlugin.kt:776)
...
See flutter/flutter/issues#21473
You need to upgrade your Kotlin version to 1.2.71+
.
If Flutter supports more platforms (Windows, Mac, Linux, etc) in the future and you use this library, propose an issue or PR!
About EXIF information #
Using this library, EXIF information will be removed.