How to convert image stream buffer into jpeg image bytes in flutter for iOS?

Question

When we deal with camera in flutter, we use Camera plugin.
It has .startImageStream method which returns CameraImage cameraImage data type.

In iOS, cameraImage.format is bgra8888.
For android cameraImage.format is yuv420.

Before encoding these formats to JPEG or PNG, we need some bytes manipulation and put each byte into image buffer, which is then used in JpegEncoder.

For android, cameraImage(yuv420) to List<int> is discussed and implemented in this issue: https://github.com/flutter/flutter/issues/26348#issuecomment-462321428

The question is, how do we construct flutter Image(jpeg|png) from bgra8888 cameraImage?

Solution

Take a look at the pub.dev image library API at https://pub.dev/packages/image. It converts from any image format, regardless of it being bgra8888 or yuv420. This example converts it to a PNG file:

import 'dart:io';
import 'package:image/image.dart';
void main() {
  // Read an image from file
  // decodeImage will identify the format of the image and use the appropriate
  // decoder.
  Image image = decodeImage(File('test.bgra8888').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));
}

Comments

[Kohls]

Op requested conversion to JPG, not PNG

[Kamlesh]

any solution for jpg image??

[rexxar]

the solution for JPG is to rename the file to thumbnail.jpg and use the encodeJpg method instead of encodePng

[Taufik Nur Rahmanda]

then how to set jpg background to white?