🟣 Kotlin로 간단한 이미지 필터링 앱 구현

// MainActivity.kt
package com.example.imagefilteringapp

import android.app.Activity
import android.content.Intent
import android.graphics.Bitmap
import android.net.Uri
import android.os.Bundle
import android.provider.MediaStore
import android.widget.ImageView
import android.widget.Toast
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity
import com.bumptech.glide.Glide
import java.io.IOException

class MainActivity : AppCompatActivity() {
    private lateinit var imageView: ImageView

    private val galleryLauncher = registerForActivityResult(
        ActivityResultContracts.GetContent()
    ) { uri ->
        if (uri != null) {
            try {
                val bitmap = MediaStore.Images.Media.getBitmap(contentResolver, uri)
                applyFilters(bitmap)
            } catch (e: IOException) {
                Toast.makeText(this, "이미지 로드 실패", Toast.LENGTH_SHORT).show()
            }
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        imageView = findViewById(R.id.imageView)
        
        // 갤러리에서 이미지 선택 버튼 클릭 이벤트
        findViewById<android.widget.Button>(R.id.selectImageButton).setOnClickListener {
            galleryLauncher.launch("image/*")
        }
    }

    private fun applyFilters(bitmap: Bitmap) {
        imageView.setImageBitmap(bitmap)

        // 블러 필터 적용
        findViewById<android.widget.Button>(R.id.blurButton).setOnClickListener {
            val blurredBitmap = blurImage(bitmap)
            imageView.setImageBitmap(blurredBitmap)
        }

        // 그레이스케일 필터 적용
        findViewById<android.widget.Button>(R.id.grayscaleButton).setOnClickListener {
            val grayBitmap = convertToGrayscale(bitmap)
            imageView.setImageBitmap(grayBitmap)
        }

        // 블랙 & 화이트 필터 적용
        findViewById< nad. blackAndWhiteButton).setOnClickListener {
            val blackWhiteBitmap = convertToBlackAndWhite(bitmap)
            imageView.setImageBitmap(blackWhiteBitmap)
        }
    }

    private fun blurImage(bitmap: Bitmap): Bitmap {
        // 실제 구현을 위해 라이브러리(예: OpenCV) 사용 권장
        return bitmap // 임시로 동일한 이미지 반환
    }

    private fun convertToGrayscale(bitmap: Bitmap): Bitmap {
        val width = bitmap.width
        val height = bitmap.height
        val grayBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
        
        for (y in 0 until height) {
            for (x in 0 until width) {
                val pixel = bitmap.getPixel(x, y)
                val r = (pixel shr 16 and 0xFF).toFloat()
                val g = (pixel shr 8 and 0xFF).toFloat()
                val b = (pixel and 0xFF).toFloat()

                // 그레이스케일 변환 (중심 가중치)
                val gray = (r * 0.299f + g * 0.587f + b * 0.114f).toInt()
                
                val grayPixel = (gray shl 16) or (gray shl 8) or gray
                grayBitmap.setPixel(x, y, grayPixel)
            }
        }
        return grayBitmap
    }

    private fun convertToBlackAndWhite(bitmap: Bitmap): Bitmap {
        val width = bitmap.width
        val height = bitmap.height
        val blackWhiteBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
        
        for (y in 0 until height) {
            for (x in 0 until width) {
                val pixel = bitmap.getPixel(x, y)
                val r = (pixel shr 16 and 0xFF).toFloat()
                val g = (pixel shr 8 and 0xFF).toFloat()
                val b = (pixel and 0xFF).toFloat()

                // 흑백 변환 (중심 가중치)
                val gray = (r * 0.299f + g * 0.587f + b * 0.114f).toInt()
                
                val blackWhitePixel = if (gray > 127) -1 else 0
                blackWhiteBitmap.setPixel(x, y, blackWhitePixel)
            }
        }
        return blackWhiteBitmap
    }
}

// activity_main.xml 예시:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <Button
        android:id="@+id/selectImageButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="이미지 선택" />

    <Button
        android:id="@+id/blurButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="블러 필터 적용" />

    <Button
        android:id="@+id/grayscaleButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="그레이스케일 필터 적용" />

    <Button
        android:id="@+id/blackAndWhiteButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="블랙 & 화이트 필터 적용" />

</LinearLayout>