image remove background in flutter

image_remove_backgroun.dart

  Future<Uint8List> _downloadImage() async {
    String dir = (await getApplicationDocumentsDirectory()).path;
    File file = new File('$dir/$_filename');

    if (file.existsSync()) {
      var image = await file.readAsBytes();
      return image;
    } else {
      var response = await http.get(_url,);
      var bytes = response.bodyBytes;
      Uint8List newPng = await removeWhiteBackground(bytes);
      file.writeAsBytes(newPng);
      return newPng;
    }
  }

  Future<Uint8List> removeWhiteBackground(Uint8List bytes) async {
    Img.Image image = Img.decodeImage(bytes);
    Img.Image transparentImage = await colorTransparent(image, 255, 255, 255);
    var newPng = Img.encodePng(transparentImage);
    return newPng;
  }

Future<Img.Image> colorTransparent(Img.Image src, int red, int green, int blue) async {
  var pixels = src.getBytes();
  for (int i = 0, len = pixels.length; i < len; i += 4) {
    if(pixels[i] == red
        && pixels[i+1] == green
        && pixels[i+2] == blue
    ) {
      pixels[i + 3] = 0;
    }
  }

  return src;
}

This is cool. Once the background is removed, how hard would it be to crop to the new boundaries? Basically, so you don't get a ton of empty space around the image?

How to crop background?

In case you are not getting the background to be turned transparent, just add this line before line 25
src.channels = Img.Channels.rgba;

this code doesn't work, what am I doing wrong guys, please, help.

// the function returns  List<int> , but should return Future<Uint8List>, makes no sence !!?? What am I missing ?

var newPng = Img.encodePng(transparentImage) ;       
return newPng ;           // List

Spent a lot of time here, giving up =[

import 'dart:typed_data';
import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';
import 'package:image/image.dart' as Img;
import 'package:http/http.dart' as http;
import 'package:path_provider/path_provider.dart';
import 'package:flutter/material.dart';
import 'package:path/path.dart';
//import 'package:file/file.dart';
import 'dart:async';
import 'dart:io';

class CriaSticker extends StatefulWidget {
  const CriaSticker({Key? key}) : super(key: key);

  @override
  State<CriaSticker> createState() => _CriaStickerState();
}

class _CriaStickerState extends State<CriaSticker> {
  @override
  Widget build(BuildContext context) {

    dynamic img = Imagem()._downloadImage();
    dynamic teste = Imagem().removeWhiteBackground(img as dynamic);
    //Future<Image> resu = Imagem().colorTransparent(teste, 110, 110, 110);

    if (kDebugMode) {
      print(img);
    }

    return const Center(child: Text('aabc',),);
  }
}


 class Imagem {

  Future<Uint8List> _downloadImage() async {
    String dir = (await getApplicationDocumentsDirectory()).path;
    //File file = File("http://photo.tuchong.com/4870004/f/298584322.jpg");

    final ByteData imageData = await NetworkAssetBundle(Uri.parse("http://photo.tuchong.com/4870004/f/298584322.jpg")).load("");
    final Uint8List finalImg = imageData.buffer.asUint8List();

    // display it with the Image.memory widget
    //var image = await file.readAsBytes();
    return finalImg;

  }

  Future<Uint8List>   removeWhiteBackground(Uint8List bytes) async {
    Img.Image? image = Img.decodeImage(bytes);
    Img.Image transparentImage = await colorTransparent(image!, 255, 255, 255);
    var newPng = Img.encodePng(transparentImage) as Future<Uint8List> ;
    return newPng ;
  }


  Future<Img.Image> colorTransparent(Img.Image src, int red, int green, int blue) async {
    var pixels = src.getBytes();
    for (int i = 0, len = pixels.length; i < len; i += 4) {
      if(pixels[i] == red
          && pixels[i+1] == green
          && pixels[i+2] == blue
      ) {
        pixels[i + 3] = 0;
      }
    }

    return src;
  }
}

@DemianGo return newPng as Uint8List;

@DemianGo could you do it? I've been trying for weeks and I can't !!!

greeting for the author for sharing this code.
i modified little things in the code and it works for me, hope this works for you.

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'dart:io';

Future<Uint8List?> removeWhiteBackground(Uint8List bytes) async {
  img.Image? image = img.decodeImage(bytes);
  img.Image? transparentImage = await colorTransparent(image!, 255, 255, 255);
  var newPng = img.encodePng(transparentImage!);
  Uint8List unit8list = Uint8List.fromList(newPng);
  return unit8list;
}


Future<Uint8List> _downloadImage() async {
  File file =File('your image path here');

  var image = await file.readAsBytes();

  return image;

}

Future<img.Image?> colorTransparent(img.Image src, int red, int green, int blue) async {
  var bytes = src.getBytes() ;
  for (int i = 0, len = bytes.length; i < len; i += 4) {
    if((bytes[i] == red&&bytes[i+1] == green&&bytes[i+2] == blue)
    ){
      bytes[i+3] = 0;
    }
  }

  return img.Image.fromBytes(src.width, src.height, bytes);
}

class RemoveBG extends StatelessWidget {
  RemoveBG({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.blue,
      body: FutureBuilder(
        future: _downloadImage(),
        builder:(context, snapshot) => snapshot.data==null?SizedBox.shrink(): FutureBuilder(
          future: removeWhiteBackground(snapshot.data!),
          builder:(context, snapshot1) =>  snapshot1.data==null?SizedBox.shrink():Container(
            child: Center(
                child: Image.memory(snapshot1.data!,)
            ),
          ),
        ),
      ),
    );
  }
}

I don't get it I cant get Img.Image to work at all and cant find the library online anywhere. Did they change it to something else?

I don't get it I cant get Img.Image to work at all and cant find the library online anywhere. Did they change it to something else?

import 'package:image/image.dart' as img;←
the img.Image will work

It's working on version 3.2.0
Not working on latest version 4.0.15

Adding it to the 25th line does not make it transparent.

Future<Img.Image> colorTransparent(Img.Image src, int red, int green, int blue) async{
    src.channels = Img.Channels.rgba;
    var pixels = src.getBytes();
    for (int i = 0, len = pixels.length; i < len; i += 4) {
      if(pixels[i] == red
          && pixels[i+1] == green
          && pixels[i+2] == blue
      ) {
        pixels[i + 3] = 0;
      }
    }

    return src;
  }

This is All code.

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:remove_background/remove_background.dart';
import 'dart:ui' as ui;

import 'package:syncfusion_flutter_signaturepad/signaturepad.dart';
import 'package:image_gallery_saver/image_gallery_saver.dart';

import 'package:image/image.dart' as Img;


class SignPage2 extends StatefulWidget {
  const SignPage2({super.key});

  @override
  State<SignPage2> createState() => _SignPage2State();
}

class _SignPage2State extends State<SignPage2> {

  final GlobalKey<SfSignaturePadState> signatureGlobalKey = GlobalKey();


  ui.Image? signImage;

  void _handleClearButtonPressed() {
    signatureGlobalKey.currentState!.clear();
  }


  //백그라운드 제거
  Future<Uint8List> removeWhiteBackground(Uint8List bytes) async {
    Img.Image? image = Img.decodeImage(bytes);
    Img.Image transparentImage = await colorTransparent(image!, 255, 255, 255);
    var newPng = Img.encodePng(transparentImage);
    return Uint8List.fromList(newPng);
  }

  Future<Img.Image> colorTransparent(Img.Image src, int red, int green, int blue) async{
    src.channels = Img.Channels.rgba;
    var pixels = src.getBytes();
    for (int i = 0, len = pixels.length; i < len; i += 4) {
      if(pixels[i] == red
          && pixels[i+1] == green
          && pixels[i+2] == blue
      ) {
        pixels[i + 3] = 0;
      }
    }

    return src;
  }

  void _handleSaveButtonPressed() async {
    final data =
        await signatureGlobalKey.currentState!.toImage(pixelRatio: 3.0);
    final bytes = await data.toByteData(format: ui.ImageByteFormat.png);

    Uint8List signImage;

    print('>>>데이터의 타입 : ${data.runtimeType}');
    if( bytes != null ){
      signImage = await removeWhiteBackground(Uint8List.fromList(bytes.buffer.asUint8List()));

      final result = await ImageGallerySaver.saveImage(Uint8List.view(signImage.buffer));

      ByteData item = await cutImage(context: context, image: data);
      
    }

    print('>>>바이트 형식 : ${bytes.runtimeType}');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("SYNCFUSION FLUTTER SIGNATUREPAD"),
      ),
      body: Center(
        child: Column(
          children: [
            Container(
              width: double.infinity,
              height: 400,
              decoration: BoxDecoration(
                border: Border.all(
                  width: 1.0, color: Colors.black, style: BorderStyle.solid
                ),
                color: Colors.blue,
              ),
              child: SfSignaturePad(
                key: signatureGlobalKey,
                backgroundColor: Colors.white,
              ),
            ),
            ElevatedButton(onPressed: _handleSaveButtonPressed, child: Text('사진 저장')),
            ElevatedButton(onPressed: _handleClearButtonPressed, child: Text('사진 초기화')),

          ],
        ),
      ),
    );
  }
}

This coded worked for me, thanks!

Its not removing background , making the shade of white greyish