How to implement a photo editor as a separate…

Create a separate Android module (library or dynamic-feature).

Main components:

Fragment or Activity: User interface of the editor.
ViewModel: Storage of state and handling editing logic.
Bitmap or ImageDecoder: Loading and manipulating images.
Classes for filters and effects: Implementation of image processing algorithms.
UI elements: ImageView for displaying the image, SeekBar for parameter adjustment, buttons for tool selection.

Example module structure (simplified):

// Module root directory
|-- src  
|   |-- main  
|       |-- java  
|           |-- com  
|               |-- yourcompany  
|                   |-- photoeditor  
|                       |-- PhotoEditorFragment.kt  // UI  
|                       |-- PhotoEditorViewModel.kt // Logic  
|                       |-- filters  
|                       |   |-- GrayscaleFilter.kt  // Example filter  
|                       |-- utils  
|                       |   |-- ImageProcessingUtil.kt // Utilities  
|       |-- res  
|           |-- layout  
|               |-- fragment_photo_editor.xml // Layout  
|           |-- values  
|               |-- strings.xml  
|               |-- styles.xml  
|   |-- AndroidManifest.xml

Module build.gradle.kts:

// build.gradle.kts of the module
plugins {
    id("com.android.library")
    kotlin("android")
    kotlin("kapt")
}

android {
    namespace = "com.yourcompany.photoeditor"
    compileSdk = 34

    defaultConfig {
        minSdk = 24
        targetSdk = 34

        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            isMinifyEnabled = false
            proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
        }
    }
    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_1_8
        targetCompatibility = JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = "1.8"
    }
    buildFeatures {
        viewBinding = true
    }
}

dependencies {
    // AndroidX
    implementation("androidx.core:core-ktx:1.12.0")
    implementation("androidx.appcompat:appcompat:1.6.1")
    implementation("androidx.fragment:fragment-ktx:1.6.1")
    implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:2.6.2")
    implementation("androidx.constraintlayout:constraintlayout:2.1.4")

    // Kotlin Coroutines
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.1")
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.1")

    // Tests
    testImplementation("junit:junit:4.13.2")
    androidTestImplementation("androidx.test.ext:junit:1.1.5")
    androidTestImplementation("androidx.test.espresso:espresso-core:3.5.1")
}

Integration:

Add the module as a dependency in app/build.gradle.kts.
Pass the image (e.g., URI) to the editor component.
The editor should provide a way to return the edited image (e.g., via setFragmentResult or ActivityResultContract).

Example of using setFragmentResult:

In the editor:

// PhotoEditorFragment.kt
private fun saveEditedImage() {
    // ... save logic ...
    val result = Bundle().apply {
        putString("edited_image_uri", editedImageUri.toString())
    }
    setFragmentResult("requestKey", result)
    parentFragmentManager.popBackStack()
}

In the calling fragment/activity:

// YourCallingFragment.kt
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setFragmentResultListener("requestKey") { requestKey, bundle ->
        val editedImageUriString = bundle.getString("edited_image_uri")
        // ... handle the edited image ...
    }
}

private fun openEditor() {
    val editorFragment = PhotoEditorFragment()
    // ... pass the original image ...
    parentFragmentManager.beginTransaction()
        .replace(R.id.fragment_container, editorFragment)
        .addToBackStack(null)  
        .commit()
}

How to implement a photo editor as a separate component in an Android application?