How to compress/reduce image sizes while uploading in Dart?

Question

How to compress/reduce image sizes while uploading in Dart? I am trying to upload a 5MB image but I want to reduce its size while uploading. I am using Dart and Flutter.

Answer 1

There is an image manipulation package on pub. It even includes an example for exactly what you want to do.

import 'dart:io' as Io;
import 'package:image/image.dart';
void main() {
  // Read an image from file (webp in this case).
  // decodeImage will identify the format of the image and use the appropriate
  // decoder.
  Image image = decodeImage(new Io.File('test.webp').readAsBytesSync());

  // Resize the image to a 120x? thumbnail (maintaining the aspect ratio).
  Image thumbnail = copyResize(image, 120);

  // Save the thumbnail as a PNG.
  new Io.File('thumbnail.png')
        ..writeAsBytesSync(encodePng(thumbnail));
}

Answer 2

For Dart

Use Image package:

With this package , you can load an image, resize it, and save it as a png:

First, add image as a dependency in your pubspec.yaml file.

Usage :

import 'dart:io';
import 'package:image/image.dart';
void main() {
  // Read an image from file (webp in this case).
  // decodeImage will identify the format of the image and use the appropriate
  // decoder.
  Image image = decodeImage(File('test.webp').readAsBytesSync());

  // Resize the image to a 120x? thumbnail (maintaining the aspect ratio).
  Image thumbnail = copyResize(image, width: 120);

  // Save the thumbnail as a PNG.
  File('thumbnail.png')..writeAsBytesSync(encodePng(thumbnail));
}

Don't use it if you would like to use this image in flutter . Use other solutions like flutter_image_compress or ResizeImage class.

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.