OpenFlutter / Flutter_image_compress
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flutter_image_compress
Compresses image as native plugin (Obj-C/Kotlin)
This library can works on Android and iOS.
- flutter_image_compress
Why don't you use dart to do it
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.
1.0.0
The 1.0.0 is null-safety version.
Please read document for null-safety information in dart or flutter.
Usage
dependencies:
flutter_image_compress: ^1.0.0-nullsafety
import 'package:flutter_image_compress/flutter_image_compress.dart';
Use as:
There are several ways to use the library api.
// 1. compress file and get Uint8List
Future<Uint8List> 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;
}
// 2. compress file and get file.
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;
}
// 3. compress asset and get Uint8List.
Future<Uint8List> testCompressAsset(String assetName) async {
var list = await FlutterImageCompress.compressAssetImage(
assetName,
minHeight: 1920,
minWidth: 1080,
quality: 96,
rotate: 180,
);
return list;
}
// 4. compress Uint8List and get another Uint8List.
Future<Uint8List> testComporessList(Uint8List 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 common params
minWidth and minHeight
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;
}
If your image width is smaller than minWidth or height samller than minHeight, scale will be 1, that is, the size will not change.
rotate
If you need to rotate the picture, use this parameter.
autoCorrectionAngle
This property only exists in the version after 0.5.0.
And for historical reasons, there may be conflicts with rotate attributes, which need to be self-corrected.
Modify rotate to 0 or autoCorrectionAngle to false.
quality
Quality of target image.
If format is png, the param will be ignored in iOS.
format
Supports jpeg or png, default is jpeg.
The format class sign enum CompressFormat.
Heif and webp Partially supported.
Webp
Support android by the system api (speed very nice).
And support iOS, but However, no system implementation, using third-party libraries used, it is not recommended due to encoding speed. In the future, libwebp by google (c / c ++) may be used to do coding work, bypassing other three-party libraries, but there is no guarantee of implementation time.
HEIF(Heic)
Heif for iOS
Only support iOS 11+.
Heif for Android
Use HeifWriter to implemation.
Only support API 28+.
And may require hardware encoder support, does not guarantee that all devices above API28 are available
inSampleSize
The param is only support android.
For a description of this parameter, see the Android official website.
keepExif
If this parameter is true, EXIF information is saved in the compressed result.
Attention should be paid to the following points:
- Default value is false.
- Even if set to true, the direction attribute is not included.
- Only support jpg format, PNG format does not support.
Result
The result of returning a List collection will not have null, but will always be an empty array.
The returned file may be null. In addition, please decide for yourself whether the file exists.
About List<int> and Uint8List
You may need to convert List<int> to Uint8List to display images.
To use Uint8List, you need import package to your code like this:
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);
}
Runtime Error
Because of some support issues, all APIs will be compatible with format and system compatibility, and an exception (UnsupportError) may be thrown, so if you insist on using webp and heic formats, please catch the exception yourself and use it on unsupported devices jpeg compression.
Example:
Future<Uint8List> compressAndTryCatch(String path) async {
Uint8List result;
try {
result = await FlutterImageCompress.compressWithFile(path,
format: CompressFormat.heic);
} on UnsupportedError catch (e) {
print(e);
result = await FlutterImageCompress.compressWithFile(path,
format: CompressFormat.jpeg);
}
return result;
}
Android
You may need to update Kotlin to version 1.3.72 or higher.
iOS
No problems currently found.
Troubleshooting or common error
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+(recommended 1.3.72).
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 by default.
EXIF information can be retained by setting keepExif to true, but not direction information.
LICENSE
The code under MIT style.
PNG/JPEG encoder
Each using system API.
Webp encoder
Use SDWebImageWebPCoder to encode the UIImage in iOS. (Under MIT)
Android code use the Android system api.
HEIF encoder
Use iOS system api in iOS.
Use HeifWriter(androidx component by Google) to encode in androidP or higher.
About Exif handle code
The iOS code was copied from dvkch/SYPictureMetadata, LICENSE
The android code was copied from flutter/plugin/image_picker and edit some. (BSD 3 style)