Background Subtraction with OpenCV and BGS Libraries

Getting Started

Please, follow the instructions to set up the environment for Linux-based systems. This installation guide is based on the official instruction, with some additions and corrections.

If you are using Windows OS follow the Building BGSLibrary with Python support on Windows section from the same instruction.

Our code is tested using Python 3.7.5, but it should also work with any other python3.x. If you'd like to check your version run:

python3 -V

Note: We assume, that your current location is learnopencv/Background-Subtraction and will refer it as work_dir.

Virtual Environment

Let's create a new virtual environment. You'll need to install virtualenv package if you don't have it:

pip install virtualenv

Now we can create a new virtualenv variable and call it env:

python3.7 -m virtualenv venv

The last thing we have to do is to activate it:

source  venv/bin/activate

To will need also to install numpy package:

pip install numpy

OpenCV

In this blog post we are using BGS Library, which is heavily based on OpenCV. That is why, we first need to build the OpenCV library. To do so:

Install dependencies:

sudo apt-get update
sudo apt-get install build-essential cmake unzip pkg-config
sudo apt-get install libjpeg-dev libpng-dev libtiff-dev
sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libv4l-dev
sudo apt-get install libxvidcore-dev libx264-dev
sudo apt-get install libgtk-3-dev
sudo apt-get install libatlas-base-dev gfortran
sudo apt-get install python3-dev

2. Download the latest OpenCV version from the official repository:

cd ~
wget -O opencv.zip https://github.com/opencv/opencv/archive/4.3.0.zip
wget -O opencv_contrib.zip https://github.com/opencv/opencv_contrib/archive/4.3.0.zip

3. Unzip the downloaded archives:

unzip opencv.zip
unzip opencv_contrib.zip

4. Rename the directories to match CMake paths:

mv opencv-4.3.0 opencv
mv opencv_contrib-4.3.0 opencv_contrib

5. Compile OpenCV Create and enter a build directory:

cd ~/opencv
mkdir build
cd build

Run CMake to configure the OpenCV build. Don't forget to set the right pass to the PYTHON_EXECUTABLE.

cmake -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=/usr/local \
    -D INSTALL_PYTHON_EXAMPLES=ON \
    -D INSTALL_C_EXAMPLES=OFF \
    -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \
    -D PYTHON_EXECUTABLE=work_dir/venv/bin/python3 \
    -D OPENCV_GENERATE_PKGCONFIG=ON \
    -D BUILD_EXAMPLES=ON ..

Check the output and make sure that everything is set correctly. After that we are ready to build it with:

make -j4

Make sure, you didn't get any errors. Then run the following commands:

sudo make install
sudo ldconfig

which creates the necessary links and cache to our freshly-built shared library.

Put lib/python3/cv2.cpython-37m-x86_64-linux-gnu.so into the virtual environment installed packages:

cp lib/python3/cv2.cpython-37m-x86_64-linux-gnu.so work_dir/venv/lib/python3.7/site-packages/cv2.so

BGS Library

Now everything is ready to build BGS Library.

Download the source code:

cd work_dir
git clone --recursive https://github.com/andrewssobral/bgslibrary.git

2. Make build folder and navigate to it:

cd bgslibrary
mkdir build && cd build

3. Run CMake to configure the build. Don't forget to set PYTHON_EXECUTABLE to your virtual environment python.

cmake -D BGS_PYTHON_SUPPORT=ON\
  -D CMAKE_INSTALL_PREFIX=/usr/local \
  -D OpenCV_DIR=~/opencv/build \
  -D PYTHON_EXECUTABLE=work_dir/venv/bin/python  ..

4. Check the output. Pay attention to the Python library status section. It should look similar to this:

-- Python library status:
--     executable: ~/env/bin/python
--     library: ~/.pyenv/versions/3.7.5/lib/libpython3.7m.so
--     include path: ~/.pyenv/versions/3.7.5/include/python3.7m

Make sure, that your python library is build as a shared library (.so file), not as a static (.a file). That might cause an error if you are using pyenv, that builds python library as a static library by default. To rebuild it as a shared library, run:

PYTHON_CONFIGURE_OPTS="--enable-shared" pyenv install --force 3.7.5

5. Build the BGS Library:

make -j4

6. Make sure, you didn't get any errors. You can check, that everything is working by running the demo script:

cd ..
python3 demo.py

Running the Demo

Python

The proposed for experiments background_subtr_opencv.py and background_subtr_bgslib.py scripts support --input_video key to customize the background subtraction pipeline. --input_video contains the path to the input video. By default its value is "space_traffic.mp4". Please, follow the below instructions for each case.

OpenCV Library

To run OpenCV case, please, choose one of the described below scenarios:

for the default input video:

python3 background_subtr_opencv.py

for the custom input video:

python3 background_subtr_opencv.py --input_video <VIDEO_PATH>

BGS Library

To run BGSLibrary case, please, choose one of the described below scenarios:

for the default input video:

python3 background_subtr_bgslib.py

for the custom input video:

python3 background_subtr_bgslib.py --input_video <VIDEO_PATH>

C++

The first step is compiling of the proposed .cpp files with the appropriate commands for each case.

OpenCV Library

To compile background_subtr_opencv.cpp you need to run the below command:

g++ background_subtr_opencv.cpp `pkg-config --cflags --libs opencv4` -o background_subtr_opencv.out -std=c++11

After background_subtr_opencv.out was obtained, we can run the BS-pipeline:

./background_subtr_opencv.out

By default space_traffic.mp4 will be used. To provide another video as input, you need to define --input key value:

./background_subtr_opencv.out --input=<VIDEO_PATH>

BGS Library

To compile background_subtr_bgslib.cpp you need to run the below command:

g++ background_subtr_bgslib.cpp `pkg-config --cflags --libs opencv4` -lbgslibrary_core  -I bgslibrary/src -o background_subtr_bgslib.out -std=c++11

After background_subtr_bgslib.out was obtained, we can run the BS-pipeline:

./background_subtr_bgslib.out

By default space_traffic.mp4 will be used. To provide another video as input, you need to define --input key value:

./background_subtr_bgslib.out --input=<VIDEO_PATH>

Link: https://github.com/spmallick/learnopencv/tree/master/Background-Subtraction

#opencv #python #computervision

What is GEEK

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Background Subtraction with OpenCV and BGS Libraries

Flutter Dev

1679035563

How to Add Splash Screen in Android and iOS with Flutter

When your app is opened, there is a brief time while the native app loads Flutter. By default, during this time, the native app displays a white splash screen. This package automatically generates iOS, Android, and Web-native code for customizing this native splash screen background color and splash image. Supports dark mode, full screen, and platform-specific options.

What's New

[BETA] Support for flavors is in beta. Currently only Android and iOS are supported. See instructions below.

You can now keep the splash screen up while your app initializes! No need for a secondary splash screen anymore. Just use the preserve and remove methods together to remove the splash screen after your initialization is complete. See details below.

Usage

Would you prefer a video tutorial instead? Check out Johannes Milke's tutorial.

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

dependencies:
  flutter_native_splash: ^2.2.19

Don't forget to flutter pub get.

1. Setting the splash screen

Customize the following settings and add to your project's pubspec.yaml file or place in a new file in your root project folder named flutter_native_splash.yaml.

flutter_native_splash:
  # This package generates native code to customize Flutter's default white native splash screen
  # with background color and splash image.
  # Customize the parameters below, and run the following command in the terminal:
  # flutter pub run flutter_native_splash:create
  # To restore Flutter's default white splash screen, run the following command in the terminal:
  # flutter pub run flutter_native_splash:remove

  # color or background_image is the only required parameter.  Use color to set the background
  # of your splash screen to a solid color.  Use background_image to set the background of your
  # splash screen to a png image.  This is useful for gradients. The image will be stretch to the
  # size of the app. Only one parameter can be used, color and background_image cannot both be set.
  color: "#42a5f5"
  #background_image: "assets/background.png"

  # Optional parameters are listed below.  To enable a parameter, uncomment the line by removing
  # the leading # character.

  # The image parameter allows you to specify an image used in the splash screen.  It must be a
  # png file and should be sized for 4x pixel density.
  #image: assets/splash.png

  # The branding property allows you to specify an image used as branding in the splash screen.
  # It must be a png file. It is supported for Android, iOS and the Web.  For Android 12,
  # see the Android 12 section below.
  #branding: assets/dart.png

  # To position the branding image at the bottom of the screen you can use bottom, bottomRight,
  # and bottomLeft. The default values is bottom if not specified or specified something else.
  #branding_mode: bottom

  # The color_dark, background_image_dark, image_dark, branding_dark are parameters that set the background
  # and image when the device is in dark mode. If they are not specified, the app will use the
  # parameters from above. If the image_dark parameter is specified, color_dark or
  # background_image_dark must be specified.  color_dark and background_image_dark cannot both be
  # set.
  #color_dark: "#042a49"
  #background_image_dark: "assets/dark-background.png"
  #image_dark: assets/splash-invert.png
  #branding_dark: assets/dart_dark.png

  # Android 12 handles the splash screen differently than previous versions.  Please visit
  # https://developer.android.com/guide/topics/ui/splash-screen
  # Following are Android 12 specific parameter.
  android_12:
    # The image parameter sets the splash screen icon image.  If this parameter is not specified,
    # the app's launcher icon will be used instead.
    # Please note that the splash screen will be clipped to a circle on the center of the screen.
    # App icon with an icon background: This should be 960×960 pixels, and fit within a circle
    # 640 pixels in diameter.
    # App icon without an icon background: This should be 1152×1152 pixels, and fit within a circle
    # 768 pixels in diameter.
    #image: assets/android12splash.png

    # Splash screen background color.
    #color: "#42a5f5"

    # App icon background color.
    #icon_background_color: "#111111"

    # The branding property allows you to specify an image used as branding in the splash screen.
    #branding: assets/dart.png

    # The image_dark, color_dark, icon_background_color_dark, and branding_dark set values that
    # apply when the device is in dark mode. If they are not specified, the app will use the
    # parameters from above.
    #image_dark: assets/android12splash-invert.png
    #color_dark: "#042a49"
    #icon_background_color_dark: "#eeeeee"

  # The android, ios and web parameters can be used to disable generating a splash screen on a given
  # platform.
  #android: false
  #ios: false
  #web: false

  # Platform specific images can be specified with the following parameters, which will override
  # the respective parameter.  You may specify all, selected, or none of these parameters:
  #color_android: "#42a5f5"
  #color_dark_android: "#042a49"
  #color_ios: "#42a5f5"
  #color_dark_ios: "#042a49"
  #color_web: "#42a5f5"
  #color_dark_web: "#042a49"
  #image_android: assets/splash-android.png
  #image_dark_android: assets/splash-invert-android.png
  #image_ios: assets/splash-ios.png
  #image_dark_ios: assets/splash-invert-ios.png
  #image_web: assets/splash-web.png
  #image_dark_web: assets/splash-invert-web.png
  #background_image_android: "assets/background-android.png"
  #background_image_dark_android: "assets/dark-background-android.png"
  #background_image_ios: "assets/background-ios.png"
  #background_image_dark_ios: "assets/dark-background-ios.png"
  #background_image_web: "assets/background-web.png"
  #background_image_dark_web: "assets/dark-background-web.png"
  #branding_android: assets/brand-android.png
  #branding_dark_android: assets/dart_dark-android.png
  #branding_ios: assets/brand-ios.png
  #branding_dark_ios: assets/dart_dark-ios.png

  # The position of the splash image can be set with android_gravity, ios_content_mode, and
  # web_image_mode parameters.  All default to center.
  #
  # android_gravity can be one of the following Android Gravity (see
  # https://developer.android.com/reference/android/view/Gravity): bottom, center,
  # center_horizontal, center_vertical, clip_horizontal, clip_vertical, end, fill, fill_horizontal,
  # fill_vertical, left, right, start, or top.
  #android_gravity: center
  #
  # ios_content_mode can be one of the following iOS UIView.ContentMode (see
  # https://developer.apple.com/documentation/uikit/uiview/contentmode): scaleToFill,
  # scaleAspectFit, scaleAspectFill, center, top, bottom, left, right, topLeft, topRight,
  # bottomLeft, or bottomRight.
  #ios_content_mode: center
  #
  # web_image_mode can be one of the following modes: center, contain, stretch, and cover.
  #web_image_mode: center

  # The screen orientation can be set in Android with the android_screen_orientation parameter.
  # Valid parameters can be found here:
  # https://developer.android.com/guide/topics/manifest/activity-element#screen
  #android_screen_orientation: sensorLandscape

  # To hide the notification bar, use the fullscreen parameter.  Has no effect in web since web
  # has no notification bar.  Defaults to false.
  # NOTE: Unlike Android, iOS will not automatically show the notification bar when the app loads.
  #       To show the notification bar, add the following code to your Flutter app:
  #       WidgetsFlutterBinding.ensureInitialized();
  #       SystemChrome.setEnabledSystemUIOverlays([SystemUiOverlay.bottom, SystemUiOverlay.top]);
  #fullscreen: true

  # If you have changed the name(s) of your info.plist file(s), you can specify the filename(s)
  # with the info_plist_files parameter.  Remove only the # characters in the three lines below,
  # do not remove any spaces:
  #info_plist_files:
  #  - 'ios/Runner/Info-Debug.plist'
  #  - 'ios/Runner/Info-Release.plist'

2. Run the package

After adding your settings, run the following command in the terminal:

flutter pub run flutter_native_splash:create

When the package finishes running, your splash screen is ready.

To specify the YAML file location just add --path with the command in the terminal:

flutter pub run flutter_native_splash:create --path=path/to/my/file.yaml

3. Set up app initialization (optional)

By default, the splash screen will be removed when Flutter has drawn the first frame. If you would like the splash screen to remain while your app initializes, you can use the preserve() and remove() methods together. Pass the preserve() method the value returned from WidgetsFlutterBinding.ensureInitialized() to keep the splash on screen. Later, when your app has initialized, make a call to remove() to remove the splash screen.

import 'package:flutter_native_splash/flutter_native_splash.dart';

void main() {
  WidgetsBinding widgetsBinding = WidgetsFlutterBinding.ensureInitialized();
  FlutterNativeSplash.preserve(widgetsBinding: widgetsBinding);
  runApp(const MyApp());
}

// whenever your initialization is completed, remove the splash screen:
    FlutterNativeSplash.remove();

NOTE: If you do not need to use the preserve() and remove() methods, you can place the flutter_native_splash dependency in the dev_dependencies section of pubspec.yaml.

4. Support the package (optional)

If you find this package useful, you can support it for free by giving it a thumbs up at the top of this page. Here's another option to support the package:

Android 12+ Support

Android 12 has a new method of adding splash screens, which consists of a window background, icon, and the icon background. Note that a background image is not supported.

Be aware of the following considerations regarding these elements:

1: image parameter. By default, the launcher icon is used:

App icon without an icon background, as shown on the left: This should be 1152×1152 pixels, and fit within a circle 768 pixels in diameter.
App icon with an icon background, as shown on the right: This should be 960×960 pixels, and fit within a circle 640 pixels in diameter.

2: icon_background_color is optional, and is useful if you need more contrast between the icon and the window background.

3: One-third of the foreground is masked.

4: color the window background consists of a single opaque color.

PLEASE NOTE: The splash screen may not appear when you launch the app from Android Studio on API 31. However, it should appear when you launch by clicking on the launch icon in Android. This seems to be resolved in API 32+.

PLEASE NOTE: There are a number of reports that non-Google launchers do not display the launch image correctly. If the launch image does not display correctly, please try the Google launcher to confirm that this package is working.

PLEASE NOTE: The splash screen does not appear when you launch the app from a notification. Apparently this is the intended behavior on Android 12: core-splashscreen Icon not shown when cold launched from notification.

Flavor Support

If you have a project setup that contains multiple flavors or environments, and you created more than one flavor this would be a feature for you.

Instead of maintaining multiple files and copy/pasting images, you can now, using this tool, create different splash screens for different environments.

Pre-requirements

In order to use the new feature, and generate the desired splash images for you app, a couple of changes are required.

If you want to generate just one flavor and one file you would use either options as described in Step 1. But in order to setup the flavors, you will then be required to move all your setup values to the flutter_native_splash.yaml file, but with a prefix.

Let's assume for the rest of the setup that you have 3 different flavors, Production, Acceptance, Development.

First this you will need to do is to create a different setup file for all 3 flavors with a suffix like so:

flutter_native_splash-production.yaml
flutter_native_splash-acceptance.yaml
flutter_native_splash-development.yaml

You would setup those 3 files the same way as you would the one, but with different assets depending on which environment you would be generating. For example (Note: these are just examples, you can use whatever setup you need for your project that is already supported by the package):

# flutter_native_splash-development.yaml
flutter_native_splash:
  color: "#ffffff"
  image: assets/logo-development.png
  branding: assets/branding-development.png
  color_dark: "#121212"
  image_dark: assets/logo-development.png
  branding_dark: assets/branding-development.png

  android_12:
    image: assets/logo-development.png
    icon_background_color: "#ffffff"
    image_dark: assets/logo-development.png
    icon_background_color_dark: "#121212"

  web: false

# flutter_native_splash-acceptance.yaml
flutter_native_splash:
  color: "#ffffff"
  image: assets/logo-acceptance.png
  branding: assets/branding-acceptance.png
  color_dark: "#121212"
  image_dark: assets/logo-acceptance.png
  branding_dark: assets/branding-acceptance.png

  android_12:
    image: assets/logo-acceptance.png
    icon_background_color: "#ffffff"
    image_dark: assets/logo-acceptance.png
    icon_background_color_dark: "#121212"

  web: false

# flutter_native_splash-production.yaml
flutter_native_splash:
  color: "#ffffff"
  image: assets/logo-production.png
  branding: assets/branding-production.png
  color_dark: "#121212"
  image_dark: assets/logo-production.png
  branding_dark: assets/branding-production.png

  android_12:
    image: assets/logo-production.png
    icon_background_color: "#ffffff"
    image_dark: assets/logo-production.png
    icon_background_color_dark: "#121212"

  web: false

Great, now comes the fun part running the new command!

The new command is:

# If you have a flavor called production you would do this:
flutter pub run flutter_native_splash:create --flavor production

# For a flavor with a name staging you would provide it's name like so:
flutter pub run flutter_native_splash:create --flavor staging

# And if you have a local version for devs you could do that:
flutter pub run flutter_native_splash:create --flavor development

Android setup

You're done! No, really, Android doesn't need any additional setup.

Note: If it didn't work, please make sure that your flavors are named the same as your config files, otherwise the setup will not work.

iOS setup

iOS is a bit tricky, so hang tight, it might look scary but most of the steps are just a single click, explained as much as possible to lower the possibility of mistakes.

When you run the new command, you will need to open xCode and follow the steps bellow:

Assumption

In order for this setup to work, you would already have 3 different schemes setup; production, acceptance and development.

Preparation

Open the iOS Flutter project in Xcode (open the Runner.xcworkspace)
Find the newly created Storyboard files at the same location where the original is {project root}/ios/Runner/Base.lproj
Select all of them and drag and drop into Xcode, directly to the left hand side where the current LaunchScreen.storyboard is located already
After you drop your files there Xcode will ask you to link them, make sure you select 'Copy if needed'
This part is done, you have linked the newly created storyboards in your project.

xCode

Xcode still doesn't know how to use them, so we need to specify for all the current flavors (schemes) which file to use and to use that value inside the Info.plist file.

Open the iOS Flutter project in Xcode (open the Runner.xcworkspace)
Click the Runner project in the top left corner (usually the first item in the list)
In the middle part of the screen, on the left side, select the Runner target
On the top part of the screen select Build Settings
Make sure that 'All' and 'Combined' are selected
Next to 'Combine' you have a '+' button, press it and select 'Add User-Defined Setting'
Once you do that Xcode will create a new variable for you to name. Suggestion is to name it LAUNCH_SCREEN_STORYBOARD
Once you do that, you will have the option to define a specific name for each flavor (scheme) that you have defined in the project. Make sure that you input the exact name of the LaunchScreen.storyboard that was created by this tool
- Example: If you have a flavor Development, there is a Storyboard created name LaunchScreenDevelopment.storyboard, please add that name (without the storyboard part) to the variable value next to the flavor value
After you finish with that, you need to update Info.plist file to link the newly created variable so that it's used correctly
Open the Info.plist file
Find the entry called 'Launch screen interface file base name'
The default value is 'LaunchScreen', change that to the variable name that you create previously. If you follow these steps exactly, it would be LAUNCH_SCREEN_STORYBOARD, so input this $(LAUNCH_SCREEN_STORYBOARD)
And your done!

Congrats you finished your setup for multiple flavors,

FAQs

I got the error "A splash screen was provided to Flutter, but this is deprecated."

This message is not related to this package but is related to a change in how Flutter handles splash screens in Flutter 2.5. It is caused by having the following code in your android/app/src/main/AndroidManifest.xml, which was included by default in previous versions of Flutter:

<meta-data
 android:name="io.flutter.embedding.android.SplashScreenDrawable"
 android:resource="@drawable/launch_background"
 />

The solution is to remove the above code. Note that this will also remove the fade effect between the native splash screen and your app.

Are animations/lottie/GIF images supported?

Not at this time. PRs are always welcome!

I got the error AAPT: error: style attribute 'android:attr/windowSplashScreenBackground' not found

This attribute is only found in Android 12, so if you are getting this error, it means your project is not fully set up for Android 12. Did you update your app's build configuration?

I see a flash of the wrong splash screen on iOS

This is caused by an iOS splash caching bug, which can be solved by uninstalling your app, powering off your device, power back on, and then try reinstalling.

I see a white screen between splash screen and app

It may be caused by an iOS splash caching bug, which can be solved by uninstalling your app, powering off your device, power back on, and then try reinstalling.
It may be caused by the delay due to initialization in your app. To solve this, put any initialization code in the removeAfter method.

Can I base light/dark mode on app settings?

No. This package creates a splash screen that is displayed before Flutter is loaded. Because of this, when the splash screen loads, internal app settings are not available to the splash screen. Unfortunately, this means that it is impossible to control light/dark settings of the splash from app settings.

Notes

If the splash screen was not updated correctly on iOS or if you experience a white screen before the splash screen, run flutter clean and recompile your app. If that does not solve the problem, delete your app, power down the device, power up the device, install and launch the app as per this StackOverflow thread.

This package modifies launch_background.xml and styles.xml files on Android, LaunchScreen.storyboard and Info.plist on iOS, and index.html on Web. If you have modified these files manually, this plugin may not work properly. Please open an issue if you find any bugs.

How it works

Android

Your splash image will be resized to mdpi, hdpi, xhdpi, xxhdpi and xxxhdpi drawables.
An <item> tag containing a <bitmap> for your splash image drawable will be added in launch_background.xml
Background color will be added in colors.xml and referenced in launch_background.xml.
Code for full screen mode toggle will be added in styles.xml.
Dark mode variants are placed in drawable-night, values-night, etc. resource folders.

iOS

Your splash image will be resized to @3x and @2x images.
Color and image properties will be inserted in LaunchScreen.storyboard.
The background color is implemented by using a single-pixel png file and stretching it to fit the screen.
Code for hidden status bar toggle will be added in Info.plist.

Web

A web/splash folder will be created for splash screen images and CSS files.
Your splash image will be resized to 1x, 2x, 3x, and 4x sizes and placed in web/splash/img.
The splash style sheet will be added to the app's web/index.html, as well as the HTML for the splash pictures.

Acknowledgments

This package was originally created by Henrique Arthur and it is currently maintained by Jon Hanson.

Bugs or Requests

If you encounter any problems feel free to open an issue. If you feel the library is missing a feature, please raise a ticket. Pull request are also welcome.

Use this package as a library

Depend on it

Run this command:

With Flutter:

 $ flutter pub add flutter_native_splash

This will add a line like this to your package's pubspec.yaml (and run an implicit flutter pub get):

dependencies:
  flutter_native_splash: ^2.2.19

Alternatively, your editor might support flutter pub get. Check the docs for your editor to learn more.

Import it

Now in your Dart code, you can use:

import 'package:flutter_native_splash/flutter_native_splash.dart';

example/lib/main.dart

import 'package:flutter/material.dart';
import 'package:flutter_native_splash/flutter_native_splash.dart';

void main() {
  WidgetsBinding widgetsBinding = WidgetsFlutterBinding.ensureInitialized();
  FlutterNativeSplash.preserve(widgetsBinding: widgetsBinding);
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }

  @override
  void initState() {
    super.initState();
    initialization();
  }

  void initialization() async {
    // This is where you can initialize the resources needed by your app while
    // the splash screen is displayed.  Remove the following example because
    // delaying the user experience is a bad design practice!
    // ignore_for_file: avoid_print
    print('ready in 3...');
    await Future.delayed(const Duration(seconds: 1));
    print('ready in 2...');
    await Future.delayed(const Duration(seconds: 1));
    print('ready in 1...');
    await Future.delayed(const Duration(seconds: 1));
    print('go!');
    FlutterNativeSplash.remove();
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Download Details:

Author: jonbhanson
Download Link: Download The Source Code
Official Website: https://github.com/jonbhanson/flutter_native_splash
License: MIT license

#flutter #ios #android

Francesco Nicolas

1651770360

Background Subtraction with OpenCV and BGS Libraries

Getting Started

Please, follow the instructions to set up the environment for Linux-based systems. This installation guide is based on the official instruction, with some additions and corrections.

If you are using Windows OS follow the Building BGSLibrary with Python support on Windows section from the same instruction.

Our code is tested using Python 3.7.5, but it should also work with any other python3.x. If you'd like to check your version run:

python3 -V

Note: We assume, that your current location is learnopencv/Background-Subtraction and will refer it as work_dir.

Virtual Environment

Let's create a new virtual environment. You'll need to install virtualenv package if you don't have it:

pip install virtualenv

Now we can create a new virtualenv variable and call it env:

python3.7 -m virtualenv venv

The last thing we have to do is to activate it:

source  venv/bin/activate

To will need also to install numpy package:

pip install numpy

OpenCV

In this blog post we are using BGS Library, which is heavily based on OpenCV. That is why, we first need to build the OpenCV library. To do so:

Install dependencies:

sudo apt-get update
sudo apt-get install build-essential cmake unzip pkg-config
sudo apt-get install libjpeg-dev libpng-dev libtiff-dev
sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libv4l-dev
sudo apt-get install libxvidcore-dev libx264-dev
sudo apt-get install libgtk-3-dev
sudo apt-get install libatlas-base-dev gfortran
sudo apt-get install python3-dev

2. Download the latest OpenCV version from the official repository:

cd ~
wget -O opencv.zip https://github.com/opencv/opencv/archive/4.3.0.zip
wget -O opencv_contrib.zip https://github.com/opencv/opencv_contrib/archive/4.3.0.zip

3. Unzip the downloaded archives:

unzip opencv.zip
unzip opencv_contrib.zip

4. Rename the directories to match CMake paths:

mv opencv-4.3.0 opencv
mv opencv_contrib-4.3.0 opencv_contrib

5. Compile OpenCV Create and enter a build directory:

cd ~/opencv
mkdir build
cd build

Run CMake to configure the OpenCV build. Don't forget to set the right pass to the PYTHON_EXECUTABLE.

cmake -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=/usr/local \
    -D INSTALL_PYTHON_EXAMPLES=ON \
    -D INSTALL_C_EXAMPLES=OFF \
    -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \
    -D PYTHON_EXECUTABLE=work_dir/venv/bin/python3 \
    -D OPENCV_GENERATE_PKGCONFIG=ON \
    -D BUILD_EXAMPLES=ON ..

Check the output and make sure that everything is set correctly. After that we are ready to build it with:

make -j4

Make sure, you didn't get any errors. Then run the following commands:

sudo make install
sudo ldconfig

which creates the necessary links and cache to our freshly-built shared library.

Put lib/python3/cv2.cpython-37m-x86_64-linux-gnu.so into the virtual environment installed packages:

cp lib/python3/cv2.cpython-37m-x86_64-linux-gnu.so work_dir/venv/lib/python3.7/site-packages/cv2.so

BGS Library

Now everything is ready to build BGS Library.

Download the source code:

cd work_dir
git clone --recursive https://github.com/andrewssobral/bgslibrary.git

2. Make build folder and navigate to it:

cd bgslibrary
mkdir build && cd build

3. Run CMake to configure the build. Don't forget to set PYTHON_EXECUTABLE to your virtual environment python.

cmake -D BGS_PYTHON_SUPPORT=ON\
  -D CMAKE_INSTALL_PREFIX=/usr/local \
  -D OpenCV_DIR=~/opencv/build \
  -D PYTHON_EXECUTABLE=work_dir/venv/bin/python  ..

4. Check the output. Pay attention to the Python library status section. It should look similar to this:

-- Python library status:
--     executable: ~/env/bin/python
--     library: ~/.pyenv/versions/3.7.5/lib/libpython3.7m.so
--     include path: ~/.pyenv/versions/3.7.5/include/python3.7m

PYTHON_CONFIGURE_OPTS="--enable-shared" pyenv install --force 3.7.5

5. Build the BGS Library:

make -j4

6. Make sure, you didn't get any errors. You can check, that everything is working by running the demo script:

cd ..
python3 demo.py

Running the Demo

Python

OpenCV Library

To run OpenCV case, please, choose one of the described below scenarios:

for the default input video:

python3 background_subtr_opencv.py

for the custom input video:

python3 background_subtr_opencv.py --input_video <VIDEO_PATH>

BGS Library

To run BGSLibrary case, please, choose one of the described below scenarios:

for the default input video:

python3 background_subtr_bgslib.py

for the custom input video:

python3 background_subtr_bgslib.py --input_video <VIDEO_PATH>

C++

The first step is compiling of the proposed .cpp files with the appropriate commands for each case.

OpenCV Library

To compile background_subtr_opencv.cpp you need to run the below command:

g++ background_subtr_opencv.cpp `pkg-config --cflags --libs opencv4` -o background_subtr_opencv.out -std=c++11

After background_subtr_opencv.out was obtained, we can run the BS-pipeline:

./background_subtr_opencv.out

By default space_traffic.mp4 will be used. To provide another video as input, you need to define --input key value:

./background_subtr_opencv.out --input=<VIDEO_PATH>

BGS Library

To compile background_subtr_bgslib.cpp you need to run the below command:

g++ background_subtr_bgslib.cpp `pkg-config --cflags --libs opencv4` -lbgslibrary_core  -I bgslibrary/src -o background_subtr_bgslib.out -std=c++11

After background_subtr_bgslib.out was obtained, we can run the BS-pipeline:

./background_subtr_bgslib.out

By default space_traffic.mp4 will be used. To provide another video as input, you need to define --input key value:

./background_subtr_bgslib.out --input=<VIDEO_PATH>

Link: https://github.com/spmallick/learnopencv/tree/master/Background-Subtraction

#opencv #python #computervision

Verda Conroy

1591743681

Create a Virtual Pen and Eraser with Python OpenCV - Genial Code

Learn Free how to create a virtual pen and eraser with python and OpenCV with source code and complete guide. This entire application is built fundamentally on contour detection. It can be thought of as something like closed color curves on compromises that have the same color or intensity, it’s like a blob. In this project we use color masking to get the binary mask of our target color pen, then we use the counter detection to find the location of this pen and the contour to find it.

#python #create virtual pen and eraser with opencv #create virtual pen and eraser with python opencv #programming #opencv #python opencv

Francesco Nicolas

1626977280

A Simple HDR Implementation on OpenCV Python

Learn how to create a high dynamic range (HDR) image using Python and OpenCV

HDR images encompass the information of multiple pictures with different exposures. In a scene which the source of light is uneven, a single shot may overexpose certain areas of the image and details will be lost due to elevated brightness. Conversely, this picture may also present underexposed areas which will also lead to information loss.

To create an HDR image you will need:

Take pictures with different exposures. Minimum of 2, generally 3, you can use more than 3 images but it will take a lot of CPU resources.
Align the images. Even if you use a tripod you will need to perform this step (we are talking about pixel level alignment). Not properly aligning your image will lead to artifacts and ‘ghosts’ in your HDR image.
Merge the aligned images into one.
Perform tone mapping on the merged image. In nature the minimum possible brightness is zero but the maximum is not limited to 255, in fact there is no limit to it, it can be infinity. For this reason we need to map the image obtained in the third step to a (0, 255) range. This can be achieved with tone mapping.

#hdr #opencv #computer-vision #python #opencv #opencv python

Hertha Walsh

1604210160

OpenCV + CUDA + AWS EC2 + (No More Tears)

By default, there is no need to enable OpenCV with CUDA for GPU processing, but during production, when you have heavy OpenCV manipulations to do on image/video files, we can make use of the OpenCV CUDA library to make those operations to run on GPU rather than CPU and it saves a lot of time.

It was not easy as it is said to connect the OpenCV library to enable it with CUDA, I had to go through a painful process for a week to establish the connection properly, also its both time & money consuming process. So this time I want to record the overall process for my future, as well as for others.

For the demonstration, I am renting an EC2 instance with a p3.8xlarge instance in the AWS, which has 4 Nvidia GPUs.

Image for post

Source — AWS EC2 Pricing

So if you need any help in starting an EC2 instance for the first time, you can refer to my previous post on Step by Step Creation of an EC2 Instance in AWS and Access it via Putty & WinSCP and during the process select the GPU instance you require.

Now after ssh-ing into the instance, before we get into the process we need to install a lot of packages to make the environment ready.

_Note: I have consolidated all the commands I ran from start to end and added them at the bottom. If you are more curious find them here in this __link _and follow along.

Run the below commands one after another on your instance and also I have attested the screenshots to compare the outputs against mine.

All the screenshots used hereafter are sourced by the author.

Step 1: Install OpenCV Dependencies, Nvidia CUDA driver, CUDA toolkit.

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install build-essential cmake unzip pkg-config
sudo apt-get install gcc-6 g++-6
sudo apt-get install screen
sudo apt-get install libxmu-dev libxi-dev libglu1-mesa libglu1-mesa-dev
sudo apt-get install libjpeg-dev libpng-dev libtiff-dev
sudo apt-get install libavcodec-dev libavformat-dev libswscale-dev libv4l-dev
sudo apt-get install libxvidcore-dev libx264-dev
sudo apt-get install libopenblas-dev libatlas-base-dev liblapack-dev gfortran
sudo apt-get install libhdf5-serial-dev
sudo apt-get install python3-dev python3-tk python-imaging-tk
sudo apt-get install libgtk-3-dev
sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt-get update
sudo apt-get install nvidia-driver-418
sudo reboot

#opencv-in-ubuntu #opencv-python #cuda #nvidia #opencv #ubuntu

Background Subtraction with OpenCV and BGS Libraries

Getting Started

Virtual Environment

OpenCV

BGS Library

Running the Demo

Python

OpenCV Library

BGS Library

C++

OpenCV Library

BGS Library

What's New

Usage

1. Setting the splash screen

2. Run the package

3. Set up app initialization (optional)

4. Support the package (optional)

Android 12+ Support

Flavor Support

Pre-requirements

Android setup

iOS setup

FAQs

I got the error "A splash screen was provided to Flutter, but this is deprecated."

Are animations/lottie/GIF images supported?

I got the error AAPT: error: style attribute 'android:attr/windowSplashScreenBackground' not found

I see a flash of the wrong splash screen on iOS

I see a white screen between splash screen and app

Can I base light/dark mode on app settings?

How it works

Android

iOS

Web

Acknowledgments

Bugs or Requests

Use this package as a library

Depend on it

Import it

Download Details:

Getting Started

Virtual Environment

OpenCV

BGS Library

Running the Demo

Python

OpenCV Library

BGS Library

C++

OpenCV Library

BGS Library

Learn how to create a high dynamic range (HDR) image using Python and OpenCV

Table of Contents:

Step 1: Install OpenCV Dependencies, Nvidia CUDA driver, CUDA toolkit.