I have an image, I want to delete pixels with drawing lines, I have done this successfully, however when I want to further develop the function of restoring deleted pixels with drawing lines, I really deadlocked and still haven’t found a solution for several days today. I look forward to receiving everyone’s help, thank you very much, I wish everyone a good day.

this is my class

 import android.content.Context
 import android.graphics.*
 import android.os.AsyncTask
 import android.util.AttributeSet
 import android.util.Pair
 import android.view.MotionEvent
 import android.view.View
 import android.widget.Button
 import java.lang.ref.WeakReference
 import java.util.*
 
 internal class DrawView(c: Context?, attrs: AttributeSet?) : View(c, attrs) {
private var livePath: Path
private var pathPaint: Paint
var currentBitmap: Bitmap? = null
    private set
private val cuts = Stack<Pair<Pair<Path, Paint>?, Bitmap?>>()
private val undoneCuts = Stack<Pair<Pair<Path, Paint>?, Bitmap?>>()
private var pathX = 0f
private var pathY = 0f
private var undoButton: Button? = null
private var redoButton: Button? = null
private var loadingModal: View? = null
private var currentAction: DrawViewAction? = null

enum class DrawViewAction {
    AUTO_CLEAR, MANUAL_CLEAR, ZOOM
}

fun setButtons(undoButton: Button?, redoButton: Button?) {
    this.undoButton = undoButton
    this.redoButton = redoButton
}

override fun onSizeChanged(newWidth: Int, newHeight: Int, oldWidth: Int, oldHeight: Int) {
    super.onSizeChanged(newWidth, newHeight, oldWidth, oldHeight)
    resizeBitmap(newWidth, newHeight)
}

override fun onDraw(canvas: Canvas) {
    super.onDraw(canvas)
    canvas.save()
    if (currentBitmap != null) {
        canvas.drawBitmap(currentBitmap!!, 0f, 0f, null)
        for (action in cuts) {
            if (action.first != null) {
                canvas.drawPath(action.first!!.first, action.first!!.second)
            }
        }
        if (currentAction == DrawViewAction.MANUAL_CLEAR) {
            canvas.drawPath(livePath, pathPaint)
        }
    }
    canvas.restore()
}

private fun touchStart(x: Float, y: Float) {
    pathX = x
    pathY = y
    undoneCuts.clear()
    redoButton!!.isEnabled = false
    if (currentAction == DrawViewAction.AUTO_CLEAR) {
        AutomaticPixelClearingTask(this).execute(
            x.toInt(), y.toInt()
        )
    } else {
        livePath.moveTo(x, y)
    }
    invalidate()
}

private fun touchMove(x: Float, y: Float) {
    if (currentAction == DrawViewAction.MANUAL_CLEAR) {
        val dx = Math.abs(x - pathX)
        val dy = Math.abs(y - pathY)
        if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
            livePath.quadTo(pathX, pathY, (x + pathX) / 2, (y + pathY) / 2)
            pathX = x
            pathY = y
        }
    }
}

private fun touchUp() {
    if (currentAction == DrawViewAction.MANUAL_CLEAR) {
        livePath.lineTo(pathX, pathY)
        cuts.push(Pair(Pair(livePath, pathPaint), null))
        livePath = Path()
        undoButton!!.isEnabled = true
    }
}

fun undo() {
    if (cuts.size > 0) {
        val cut = cuts.pop()
        if (cut.second != null) {
            undoneCuts.push(
                Pair(
                    null, currentBitmap
                )
            )
            currentBitmap = cut.second
        } else {
            undoneCuts.push(cut)
        }
        if (cuts.isEmpty()) {
            undoButton!!.isEnabled = false
        }
        redoButton!!.isEnabled = true
        invalidate()
    }
    //toast the user
}

fun redo() {
    if (undoneCuts.size > 0) {
        val cut = undoneCuts.pop()
        if (cut.second != null) {
            cuts.push(
                Pair(
                    null, currentBitmap
                )
            )
            currentBitmap = cut.second
        } else {
            cuts.push(cut)
        }
        if (undoneCuts.isEmpty()) {
            redoButton!!.isEnabled = false
        }
        undoButton!!.isEnabled = true
        invalidate()
    }
    //toast the user
}

override fun onTouchEvent(ev: MotionEvent): Boolean {
    if (currentBitmap != null && currentAction != DrawViewAction.ZOOM) {
        when (ev.action) {
            MotionEvent.ACTION_DOWN -> {
                touchStart(ev.x, ev.y)
                return true
            }

            MotionEvent.ACTION_MOVE -> {
                touchMove(ev.x, ev.y)
                invalidate()
                return true
            }

            MotionEvent.ACTION_UP -> {
                touchUp()
                invalidate()
                return true
            }
        }
    }
    return super.onTouchEvent(ev)
}

private fun resizeBitmap(width: Int, height: Int) {
    if (width > 0 && height > 0 && currentBitmap != null) {
        currentBitmap = BitmapUtility.getResizedBitmap(currentBitmap!!, width, height)
        currentBitmap!!.setHasAlpha(true)
        invalidate()
    }
}

fun setBitmap(bitmap: Bitmap?) {
    currentBitmap = bitmap
    resizeBitmap(width, height)
}

fun setAction(newAction: DrawViewAction?) {
    currentAction = newAction
}

fun setStrokeWidth(strokeWidth: Int) {
    pathPaint = Paint(pathPaint)
    pathPaint.strokeWidth = strokeWidth.toFloat()
}

fun setLoadingModal(loadingModal: View?) {
    this.loadingModal = loadingModal
}

private class AutomaticPixelClearingTask(drawView: DrawView) :
    AsyncTask<Int?, Void?, Bitmap>() {
    private val drawViewWeakReference: WeakReference<DrawView> = WeakReference(drawView)
    override fun onPreExecute() {
        super.onPreExecute()
        drawViewWeakReference.get()!!.loadingModal!!.visibility = VISIBLE
        drawViewWeakReference.get()!!.cuts.push(
            Pair(
                null, drawViewWeakReference.get()!!.currentBitmap
            )
        )
    }

    override fun doInBackground(vararg points: Int?): Bitmap? {
        val oldBitmap = drawViewWeakReference.get()!!.currentBitmap
        val colorToReplace = oldBitmap!!.getPixel(points[0]!!, points[1]!!)
        val width = oldBitmap.width
        val height = oldBitmap.height
        val pixels = IntArray(width * height)
        oldBitmap.getPixels(pixels, 0, width, 0, 0, width, height)
        val rA = Color.alpha(colorToReplace)
        val rR = Color.red(colorToReplace)
        val rG = Color.green(colorToReplace)
        val rB = Color.blue(colorToReplace)
        var pixel: Int

        // iteration through pixels
        for (y in 0 until height) {
            for (x in 0 until width) {
                // get current index in 2D-matrix
                val index = y * width + x
                pixel = pixels[index]
                val rrA = Color.alpha(pixel)
                val rrR = Color.red(pixel)
                val rrG = Color.green(pixel)
                val rrB = Color.blue(pixel)
                if (rA - COLOR_TOLERANCE < rrA && rrA < rA + COLOR_TOLERANCE && rR - COLOR_TOLERANCE < rrR && rrR < rR + COLOR_TOLERANCE && rG - COLOR_TOLERANCE < rrG && rrG < rG + COLOR_TOLERANCE && rB - COLOR_TOLERANCE < rrB && rrB < rB + COLOR_TOLERANCE) {
                    pixels[index] = Color.TRANSPARENT
                }
            }
        }
        val newBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888)
        newBitmap.setPixels(pixels, 0, width, 0, 0, width, height)
        return newBitmap
    }

    override fun onPostExecute(result: Bitmap) {
        super.onPostExecute(result)
        drawViewWeakReference.get()!!.currentBitmap = result
        drawViewWeakReference.get()!!.undoButton!!.isEnabled = true
        drawViewWeakReference.get()!!.loadingModal!!.visibility = INVISIBLE
        drawViewWeakReference.get()!!.invalidate()
    }

}

companion object {
    private const val TOUCH_TOLERANCE = 4f
    private const val COLOR_TOLERANCE = 20f
}

init {
    livePath = Path()
    pathPaint = Paint(Paint.ANTI_ALIAS_FLAG)
    pathPaint.isDither = true
    pathPaint.color = Color.TRANSPARENT
    pathPaint.xfermode = PorterDuffXfermode(PorterDuff.Mode.CLEAR)
    pathPaint.style = Paint.Style.STROKE
    pathPaint.strokeJoin = Paint.Join.ROUND
    pathPaint.strokeCap = Paint.Cap.ROUND
}
}

I want it to look like this