# Add Color

**Painter.kt**

/**
 *Created by Nhien Nguyen on 8/19/2022
 */
import android.graphics.Canvas
import android.graphics.Paint
import android.util.Log
import androidx.annotation.ColorInt
import com.annhienktuit.domain.models.EPointF
import com.annhienktuit.muzikv2.enums.Interpolation
import com.annhienktuit.muzikv2.utils.VisualizerHelper
import com.annhienktuit.muzikv2.utils.maths.interpolation.AkimaSplineInterpolator
import com.annhienktuit.muzikv2.utils.maths.interpolation.LinearInterpolator
import com.annhienktuit.muzikv2.utils.maths.polynomials.PolynomialSplineFunction
import java.util.Arrays
import kotlin.math.cos
import kotlin.math.sin

abstract class Painter {

    open var visualizerMaxHeight = 0
    open var discRadius = 0
    open var discMargin = 0
    open var isPlaying = false
    abstract var paint: Paint
    private val li = LinearInterpolator()
    private val sp = AkimaSplineInterpolator()
    private val quietThreshold = 5f
    private var patched: FloatArray = FloatArray(DEFAULT_PATCHED_SIZE)
    private var psf: PolynomialSplineFunction? = null
    private var nRaw: Int = 0
    private var xRaw = DoubleArray(0)
    private var yRaw = DoubleArray(0)

    //Fields for normalization
    private var max = 0F
    private var min = 0F

    open fun setPaintColor(@ColorInt vararg color: Int) {
        if(color.isEmpty()) return
        this.paint.color = color[0]
    }

    /**
     * An abstract function that every painters must implement and do their calculation there.
     *
     * @param helper the visualizerHelper from VisualizerView
     */
    abstract fun calc(helper: VisualizerHelper)

    /**
     * An abstract function that every painters must implement and do their drawing there.
     *
     * @param canvas the canvas from VisualizerView
     */
    abstract fun draw(canvas: Canvas, width: Int = 0, height: Int = 0, drawWithoutCalc: Boolean = false)

    /**
     * Interpolate FFT spectrum
     *
     * Android don't capture a high resolution spectrum, and we want the number of bands be adjustable,
     * so we do an interpolation here.
     *
     * (For example, to show 64 bands at frequencies from 0Hz to 1200Hz, Android only return ~10 FFT values.
     * So we need to interpolate those ~10 values into 64 values in order to fit it into our bands)
     *
     * @param gravityModels Array of gravityModel
     * @param sliceNum Number of Slice
     * @param interpolator Which interpolator to use, `li` for Linear, `sp` for Spline
     *
     * @return a `PolynomialSplineFunction` (psf). To get the value, use
     * `psf.value(x)`, where `x` must be a Double value from 0 to `num`
     */
    fun interpolateFft(
        gravityModels: Array<GravityModel>, sliceNum: Int, interpolator: Interpolation
    ): PolynomialSplineFunction? {
        if (gravityModels.size != nRaw) {
            nRaw = gravityModels.size
            xRaw = DoubleArray(nRaw) { (it * sliceNum).toDouble() / (nRaw - 1) }
            yRaw = DoubleArray(nRaw)
        } else {
            xRaw.forEach {
                (it * sliceNum) / (nRaw - 1)
            }
        }
        gravityModels.forEachIndexed { index, bar -> yRaw[index] = bar.height.toDouble() }
        psf = when (interpolator) {
            Interpolation.LINEAR -> li.interpolate(xRaw, yRaw)
            Interpolation.SPLINE -> sp.interpolate(xRaw, yRaw)
        }
        return psf
    }

    /**
     * Interpolate FFT spectrum (Circle)
     *
     * Similar to `interpolateFft()`. However this is meant for Fft from `getCircleFft()`
     *
     * @param gravityModels Array of gravityModel
     * @param sliceNum Number of Slice
     * @param interpolator Which interpolator to use, `li` for Linear, `sp` for Spline
     *
     * @return a `PolynomialSplineFunction` (psf). To get the value, use
     * `psf.value(x)`, where `x` must be a Double value from 0 to `num`
     */
    fun interpolateFftCircle(
        gravityModels: Array<GravityModel>, sliceNum: Int, interpolator: Interpolation
    ): PolynomialSplineFunction? {
        if (gravityModels.size != nRaw) {
            nRaw = gravityModels.size
            xRaw = DoubleArray(nRaw) { ((it - 1) * sliceNum).toDouble() / (nRaw - 1 - 2) }
            yRaw = DoubleArray(nRaw)
        } else {
            xRaw.forEach {
                ((it - 1) * sliceNum) / (nRaw - 1 - 2)
            }
        }
        gravityModels.forEachIndexed { index, bar -> yRaw[index] = bar.height.toDouble() }
        psf = when (interpolator) {
            Interpolation.LINEAR -> li.interpolate(xRaw, yRaw)
            Interpolation.SPLINE -> sp.interpolate(xRaw, yRaw)
        }
        return psf
    }

    /**
     * Check if it's quiet enough such that we can skip the drawing
     * @param fft Fft
     * @return true if it's quiet, false otherwise
     */
    fun isQuiet(fft: FloatArray): Boolean {
        fft.forEach { if (it > quietThreshold) return false }
        Log.i("IsQuiet", "True")
        return true
    }

    /**
     * Check if it's silence enough?
     * If true, we suppress all to 0 for easier visualizer
     */
    fun isSilence(fft: FloatArray): Boolean {
        if(fft.isEmpty()) return false
        if(getAverage(fft) > LOW_VALUE_THRESHOLD) return false
        return true
    }

    private fun getAverage(fft: FloatArray):Float {
        var sum = 0F
        for(idx in fft.indices){
            sum += fft[idx]
        }
        return sum / fft.size
    }

    fun suppressLowValue(fft: FloatArray){
        Arrays.fill(fft, 0F)
    }

    /**
     * Convert Polar to Cartesian
     * @param radius Radius
     * @param theta Theta
     * @return Pair of (x,y) of Cartesian
     */
    fun toCartesian(radius: Float, theta: Float): Pair<Float, Float> {
        return Pair(radius * cos(theta), radius * sin(theta))
    }

    /**
     * Convert Polar to Cartesian
     * @param radius Radius
     * @param theta Theta
     * @return [EPointF] of (x,y) of Cartesian
     */
    fun toCartesianEpointF(radius: Float, theta: Float): EPointF{
        return EPointF(radius * cos(theta), radius * sin(theta))
    }

    /**
     * Patch the Fft so that the start and the end connect perfectly. Use this with `interpolateFftCircle()`
     *
     * `[0, 1, ..., n] -> [n-1, 0, 1, ..., n-1, 0, 1]`
     *
     * @param fft Fft
     * @return CircleFft
     */
    fun getCircleFft(fft: FloatArray, updateArraySize: Boolean = false): FloatArray {
        if (updateArraySize) {
            patched = FloatArray(fft.size + 2)
        }
        fft.forEachIndexed { index, item -> patched[index + 1] = item }
        patched[0] = fft[fft.lastIndex - 1]
        patched[patched.lastIndex - 1] = fft[0]
        patched[patched.lastIndex] = fft[1]
        return patched
    }

    /**
     * Boost high values while suppress low values, generally give a powerful feeling
     * @param fft Fft
     * @param power Parameter, adjust to fit your liking
     * @return PowerFft
     */
    fun getPowerFft(fft: FloatArray, power: Float = 100.0F): FloatArray {
        return fft.map { it * it / power }.toFloatArray()
    }

    /**
     * Draw the circle visualizer
     * @param xR The ratio of X position to the canvas.width (= the width of the visualizer's view)
     * For example, 0f mean the start/left, while 1f mean the end/right of the screen.
     * @param yR The ratio of Y position to the canvas.height (= the height of the visualizer's view)
     * For example, 0f mean the top, while 1f mean the bottom of the screen.
     */
    fun drawHelperCircleLine(
        canvas: Canvas, xR: Float, yR: Float, drawCircleLine: () -> Unit
    ) {
        canvas.save()
        canvas.translate(canvas.width * xR, canvas.height * yR)
        drawCircleLine()
    }

    fun minMaxNormalizeEpointF(points: Array<EPointF>, maxLimit: Int, minLimit: Int = 0){
        min = Float.MAX_VALUE
        max = Float.MIN_VALUE
        for(point in points){
            if(point.x > max) max = point.x
            if(point.x < min) min = point.x
        }
        // We only do normalization if max element data is reached out limit
        if(max > maxLimit){
            for(idx in points.indices){
                points[idx].setX(
                    ((points[idx].x - min) / (max - min)) * maxLimit + minLimit
                )
            }
        }
    }

    /**
     * A model with gravity. Useful to smooth raw Fft values.
     */
    class GravityModel(
        var height: Float = 0f,
        var dy: Float = 0f,
        var ay: Float = 2f
    ) {
        fun update(h: Float) {
            if (h > height) {
                height = h
                dy = 0f
            }
            height -= dy
            dy += ay
            if (height < 0) {
                height = 0f
                dy = 0f
            }
        }

        override fun toString(): String {
            return "@GravityModel[Height: $height, dy: $dy, ay: $ay]"
        }
    }

    companion object{
        private const val LOW_VALUE_THRESHOLD = 7F
        private const val DEFAULT_PATCHED_SIZE = 100
    }
}

**Elastic.kt**

import android.graphics.Color
import android.util.Log
import com.annhienktuit.muzikv2.enums.Interpolation
import com.annhienktuit.muzikv2.ui.views.visualizer.nextgen.StretchAnimation
import com.annhienktuit.muzikv2.ui.views.visualizer.nextgen.painters.Painter
import com.annhienktuit.muzikv2.utils.VisualizerHelper
import com.annhienktuit.muzikv2.utils.maths.polynomials.PolynomialSplineFunction

/**
 *Created by Nhien Nguyen on 9/30/2022
 */
class Elastic(
    private var painter: Painter,
    private var startHz: Int,
    private var endHz: Int,
    private var helper: VisualizerHelper,
    private var visualizerMaxHeight: Int,
    private val ampR: Float = 0.75f,
    var color: Int = Color.WHITE,
) {
    private var gravityPoints = Array(0) {
        Painter.GravityModel(0f)
    }

    //The rate of amplification
    private lateinit var fft: FloatArray

    // Fields for normalization
    private var min = 0f
    private var max = 0f
    private val highFreqDelta = 20

    fun calculateCurve(updateArray: Boolean = false): PolynomialSplineFunction? {
        fft = helper.getFftMagnitudeRange(startHz, endHz)
        fft = painter.getCircleFft(fft, updateArray)
        minMaxNormalize(fft, visualizerMaxHeight, 0)
        if (gravityPoints.size != fft.size) {
            gravityPoints = Array(fft.size) {
                Painter.GravityModel(0f)
            }
        }
        gravityPoints.forEachIndexed { index, bar ->
            bar.update(fft[index] * ampR / 1.5F)
        }

        return painter.interpolateFft(
            gravityPoints,
            StretchAnimation.numberOfDot,
            Interpolation.SPLINE
        )
    }

    /**
     * Apply min-max normalization then handle if its value is "high frequency" continuously
     * @see <a href="https://towardsdatascience.com/everything-you-need-to-know-about-min-max-normalization-in-python-b79592732b79">Min-Max Normalization </a> <br>
     * <p> A data is defined to be "high frequency" if its value is in range <br> [[visualizerMaxHeight] - [highFreqDelta] , [visualizerMaxHeight]] </p>
     */
    private fun minMaxNormalize(fftData: FloatArray, maxLimit: Int, minLimit: Int = 0) {
        min = Float.MAX_VALUE
        max = Float.MIN_VALUE
        for (value in fftData) {
            if (value > max) max = value
            if (value < min) min = value
        }
        if (max > visualizerMaxHeight) {
            Log.i("Normalization", "Need normalize")
            for (idx in fftData.indices) {
                fftData[idx] = ((fftData[idx] - min) / (max - min)) * maxLimit + minLimit
            }
        }
    }
}

**StretchAnimation.kt**

import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import androidx.core.graphics.ColorUtils
import com.annhienktuit.domain.models.EPointF
import com.annhienktuit.muzikv2.R
import com.annhienktuit.muzikv2.ui.views.visualizer.nextgen.models.Elastic
import com.annhienktuit.muzikv2.ui.views.visualizer.nextgen.painters.Painter
import com.annhienktuit.muzikv2.utils.VisualizerHelper
import com.annhienktuit.muzikv2.utils.audiovisualizer.PolyBezierPathUtil
import com.annhienktuit.muzikv2.utils.maths.polynomials.PolynomialSplineFunction
import kotlin.math.PI
import kotlin.properties.Delegates

/**
 *Created by Nhien Nguyen on 9/30/2022
 */
class StretchAnimation(
    var context: Context,
    override var paint: Paint = Paint(Paint.ANTI_ALIAS_FLAG),
) : Painter() {
    private var elasticBands = arrayOf<Elastic>()
    var elasticCurveUtils = arrayOfNulls<PolynomialSplineFunction>(4)
    private var polyPathsUtil = PolyBezierPathUtil()
    private var paintList = Array(numberOfBand) { Paint(Paint.ANTI_ALIAS_FLAG) }
    private val barWidth =
        context.resources.getDimensionPixelSize(R.dimen.default_visualizer_bar_width).toFloat()
    private val radiusR: Float = .4f
    private val angleOffset = 2 * PI.toFloat() / numberOfDot
    private var shortest = 0F
    override var discRadius = 0
        set(value) {
            field = value
            shortest = getShortest()
            adjustRadius(shortest)
        }
    override var isPlaying = false
    var firstTimeRunning = true
    private var currentHeight = 0
    private var currentWidth = 0
    private var currentRadius by Delegates.notNull<Float>()
    private var actualBarHeight = 0F
    private var scale = 1F
    var defaultBlendColor = Color.parseColor("#707070")

    init {
        for (paint in paintList) {
            paint.apply {
                style = Paint.Style.STROKE
                strokeWidth = barWidth / 2
                strokeCap = Paint.Cap.ROUND
                alpha = 150
            }
        }
    }

    override fun calc(helper: VisualizerHelper) {
        if (elasticBands.size < numberOfBand) {
            initElasticBands(helper)
            setPaintsColor()
        }
        for (idx in elasticBands.indices) {
            if (firstTimeRunning) {
                elasticCurveUtils[idx] = elasticBands[idx].calculateCurve(true)!!
            } else {
                elasticCurveUtils[idx] = elasticBands[idx].calculateCurve(false)!!
            }
        }
    }

    override fun draw(canvas: Canvas, width: Int, height: Int, drawWithoutCalc: Boolean) {
        if (drawWithoutCalc) {
            drawHelperCircleLine(canvas, .5f, .5f) {
                // Still need to run this function to do the translate, but we don't update data on the first time
                // Otherwise, it will draw in somewhere psychically
            }
            return
        }
        if (firstTimeRunning) {
            shortest = Integer.min(width, height).toFloat()
            adjustRadius(shortest)
            currentWidth = width
            currentHeight = height
        }
        drawHelperCircleLine(canvas, .5f, .5f) {
            if (!firstTimeRunning) {
                for (i in elasticBands.indices) {
                    for (j in 0 until numberOfDot) {
                        points[i][j] = toCartesianEpointF(
                            shortest / 2.2f * (radiusR + 0.03F) + elasticCurveUtils[i]?.value(j.toDouble())
                            !!.toFloat(), angleOffset * j
                        )
                    }
                    points[i][numberOfDot] = points[i][0]
                }
            }
        }
        makeSureViewNotOutOfBound()
        for (idx in elasticBands.indices) {
            canvas.drawPath(
                polyPathsUtil.computePathThroughKnots(points[idx]), paintList[idx]
            )
        }
        if (firstTimeRunning) firstTimeRunning = false
    }

    private fun makeSureViewNotOutOfBound() {
        for (i in elasticBands.indices) {
            for (j in 0 until numberOfDot) {
                actualBarHeight =
                    (points[i][j].distanceFrom(centerPoint) - discMargin - discRadius - pointRadius * 2)
                if (actualBarHeight > visualizerMaxHeight) {
                    scale = visualizerMaxHeight / actualBarHeight
                    points[i][j] = points[i][j].scaleBy(scale)
                }
            }
        }
    }

    private fun setPaintsColor() {
        for (idx in paintList.indices) {
            paintList[idx].color = elasticBands[idx].color
        }
    }

    private fun initElasticBands(helper: VisualizerHelper) {
        elasticBands = arrayOf(
            Elastic(
                this,
                20,
                2000,
                helper,
                visualizerMaxHeight,
                1.25f,
            ),
            Elastic(
                this,
                2000,
                4000,
                helper,
                visualizerMaxHeight
            ),
            Elastic(
                this,
                4000,
                6000,
                helper,
                visualizerMaxHeight,
            ),
            Elastic(
                this,
                6000,
                10000,
                helper,
                visualizerMaxHeight,
            )
        )
    }

    /**
     * Calculate the new radius between 2 opposite point in circle
     * Then scale [shortest] based on ratio between new radius and old radius
     */
    private fun adjustRadius(minValue: Float) {
        val firstPoint = toCartesian(minValue / 2f * radiusR, angleOffset * 0)
        val secondPoint = toCartesian(minValue / 2f * radiusR, angleOffset * (numberOfDot / 2))
        currentRadius = (firstPoint.first - secondPoint.first) / 2
        val newRadius: Float
        if (currentRadius < discRadius) {
            newRadius = discRadius.toFloat() + discMargin
            val ratio = (newRadius / currentRadius)
            this.shortest *= ratio
        }
    }

    private fun getShortest(): Float = Integer.min(currentWidth, currentHeight).toFloat()

    override fun setPaintColor(vararg color: Int) {
        var initAlpha = 250
        var blendRatio = 1f
        for (painter in paintList) {
            painter.color = ColorUtils.blendARGB(Color.parseColor("#ffffff"), color[0], blendRatio)
            painter.alpha = initAlpha
            initAlpha -= 50
            blendRatio -= 0.25f
            if (initAlpha < 20) initAlpha = 20
            if (blendRatio <= 0) blendRatio = 0f
        }
    }

    companion object {
        private const val TAG = "StretchAnimation"
        private const val pointRadius = 4f
        private val centerPoint = EPointF(0F, 0F)
        private const val numberOfBand: Int = 4
        const val numberOfDot: Int = 100
        val points = Array(numberOfBand) {
            Array(numberOfDot + 1) {
                EPointF()
            }
        }
    }
}

**ParticleAnimation.kt**

import android.content.Context
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Paint
import com.annhienktuit.domain.models.EPointF
import com.annhienktuit.muzikv2.R
import com.annhienktuit.muzikv2.enums.Interpolation
import com.annhienktuit.muzikv2.ui.views.visualizer.nextgen.painters.Painter
import com.annhienktuit.muzikv2.utils.VisualizerHelper
import com.annhienktuit.muzikv2.utils.audiovisualizer.PolyBezierPathUtil
import com.annhienktuit.muzikv2.utils.maths.polynomials.PolynomialSplineFunction
import java.util.Random
import kotlin.math.PI

/**
 *Created by Nhien Nguyen on 9/26/2022
 */
class ParticleAnimation(
    var context: Context,
    override var paint: Paint = Paint(Paint.ANTI_ALIAS_FLAG),
    private var startHz: Int = 20,
    private var endHz: Int = 2000,
    private var interpolator: Interpolation = Interpolation.SPLINE,
) : Painter() {
    private var upperGravityPoints = Array(0) { GravityModel(0f) }
    private val barWidth =
        context.resources.getDimensionPixelSize(R.dimen.default_visualizer_bar_width).toFloat()
    private val radiusR: Float = .4f
    private val ampR: Float = 1f //The rate of amplification
    private val angleOffset = 2 * PI.toFloat() / numberOfDot
    private var shortest = 0F
    override var discRadius = 0
        set(value) {
            field = value
            shortest = getShortest()
            adjustRadius(shortest)
        }
    override var isPlaying = false
    var firstTimeRunning = true
    private var currentHeight = 0
    private var currentWidth = 0
    lateinit var upperFFT: FloatArray
    var upperCurveUtil: PolynomialSplineFunction? = null

    // Fields for normalization
    private var min = 0f
    private var max = 0f
    private val highFreqDelta = 20
    private var frequencyMap = HashMap<Int, Int>()
    private var random = Random()
    private var actualBarHeight = 0F
    private var scale = 1F

    //Fields for bottom animator
    private var bottomLinePaint = Paint(Paint.ANTI_ALIAS_FLAG)
    lateinit var bottomFFT: FloatArray
    private var polyPathsUtil = PolyBezierPathUtil()
    var bottomCurveUtil: PolynomialSplineFunction? = null
    private var bottomStartHZ = 8000
    private var bottomEndHz = 10000
    private var bottomGravityPoints = Array(0) { GravityModel(0f) }

    //Fields for spears
    private var spearPaint = Paint(Paint.ANTI_ALIAS_FLAG)

    init {
        paint.apply {
            color = Color.parseColor(visualizerColor)
            style = Paint.Style.FILL
            strokeWidth = barWidth
            strokeCap = Paint.Cap.ROUND
            alpha = PAINT_ALPHA
        }
        bottomLinePaint.apply {
            color = Color.parseColor(visualizerColor)
            style = Paint.Style.STROKE
            strokeWidth = barWidth / 2
            strokeCap = Paint.Cap.ROUND
            alpha = BOTTOM_PAINT_ALPHA
        }
        spearPaint.apply {
            color = Color.parseColor(visualizerColor)
            style = Paint.Style.FILL
            strokeWidth = barWidth / 2
            strokeCap = Paint.Cap.ROUND
            alpha = SPEAR_PAINT_ALPHA
        }
    }

    override fun calc(helper: VisualizerHelper) {
        calcForUpperAnimator(helper)
        calcForBottomAnimator(helper)
    }

    private fun calcForBottomAnimator(helper: VisualizerHelper) {
        bottomFFT = (helper.getFftMagnitudeRange(bottomStartHZ, bottomEndHz))
        bottomFFT = getCircleFft(bottomFFT)
        if (bottomGravityPoints.size != bottomFFT.size) {
            bottomGravityPoints = Array(bottomFFT.size) {
                GravityModel(0F)
            }
        }
        bottomGravityPoints.forEachIndexed { index, bar ->
            bar.update(bottomFFT[index] * ampR / 1.5F)
        }
        bottomCurveUtil = interpolateFft(bottomGravityPoints, numberOfDot / 5, interpolator)
    }

    private fun calcForUpperAnimator(helper: VisualizerHelper) {
        upperFFT = helper.getFftMagnitudeRange(startHz, endHz)
        upperFFT = getPowerFft(upperFFT)
        upperFFT = if (firstTimeRunning) {
            getCircleFft(upperFFT, true)
        } else {
            getCircleFft(upperFFT)
        }
        minMaxNormalize(upperFFT, visualizerMaxHeight, 0)
        if (upperGravityPoints.size != upperFFT.size) upperGravityPoints = Array(upperFFT.size) {
            GravityModel(
                0f
            )
        }
        upperGravityPoints.forEachIndexed { index, bar -> bar.update(upperFFT[index] * ampR) }
        upperCurveUtil = interpolateFftCircle(upperGravityPoints, numberOfDot, interpolator)
    }

    override fun draw(canvas: Canvas, width: Int, height: Int, drawWithoutCalc: Boolean) {
        if (drawWithoutCalc) {
            drawHelperCircleLine(canvas, .5f, .5f) {
                // Still need to run this function to do the translate, but we don't update data on the first time
                // Otherwise, it will draw in somewhere psychically
            }
            return
        }
        currentWidth = width
        currentHeight = height
        if (firstTimeRunning) {
            shortest = Integer.min(width, height).toFloat()
            adjustRadius(shortest)
        }
        drawHelperCircleLine(canvas, .5f, .5f) {
            if (!firstTimeRunning) {
                for (idx in 0 until numberOfDot) {
                    //TODO: Replace these magic numbers
                    upperPoints[idx] = toCartesianEpointF(
                        shortest / 2f * (radiusR + 0.03F) + upperCurveUtil?.value(idx.toDouble())!!
                            .toFloat(), angleOffset * idx
                    )
                    bottomPoints[idx] = toCartesianEpointF(
                        shortest / 2.4f * (radiusR + 0.03F) + bottomCurveUtil?.value(idx.toDouble())!!
                            .toFloat(), angleOffset * idx
                    )
                }
            }
        }
        upperPoints[numberOfDot] = upperPoints[0]
        bottomPoints[numberOfDot] = bottomPoints[0] // we do this to connect the begin-end of line
        makeSureViewNotOutOfBound()
        for (idx in upperPoints.indices) {
            canvas.drawCircle(upperPoints[idx].x, upperPoints[idx].y, pointRadius, paint)
        }
        canvas.drawPath(
            polyPathsUtil.computePathThroughKnots(bottomPoints), bottomLinePaint
        )
        drawSpears(canvas)
        if (firstTimeRunning) firstTimeRunning = false
    }

    private fun drawSpears(canvas: Canvas) {
        for (idx in bottomPoints.indices) {
            if (upperPoints[idx].distanceFrom(bottomPoints[idx]) > drawSpearThreshold) {
                canvas.drawLine(
                    upperPoints[idx].x,
                    upperPoints[idx].y,
                    (bottomPoints[idx].x + upperPoints[idx].x) / 2,
                    (bottomPoints[idx].y + upperPoints[idx].y) / 2,
                    spearPaint
                )
            }
        }
    }

    /**
     * Check whether the current bar is over [visualizerMaxHeight]
     * If true, scale tp fit [visualizerMaxHeight]
     */
    private fun makeSureViewNotOutOfBound() {
        for (idx in upperPoints.indices) {
            actualBarHeight =
                (upperPoints[idx].distanceFrom(centerPoint) - discMargin - discRadius - pointRadius * 2)
            if (actualBarHeight > visualizerMaxHeight) {
                scale = visualizerMaxHeight / actualBarHeight
                upperPoints[idx] = upperPoints[idx].scaleBy(scale)
            }
        }
    }

    /**
     * Calculate the new radius between 2 opposite point in circle
     * Then scale [shortest] based on ratio between new radius and old radius
     */
    private fun adjustRadius(minValue: Float) {
        val firstPoint = toCartesian(minValue / 2f * radiusR, angleOffset * 0)
        val secondPoint = toCartesian(minValue / 2f * radiusR, angleOffset * (numberOfDot / 2))
        val currentRadius = (firstPoint.first - secondPoint.first) / 2
        val newRadius: Float
        if (currentRadius < discRadius) {
            newRadius = discRadius.toFloat() + discMargin
            val ratio = (newRadius / currentRadius)
            this.shortest *= ratio
        }
    }

    /**
     * Apply min-max normalization then handle if its value is "high frequency" continuously
     * @see <a href="https://towardsdatascience.com/everything-you-need-to-know-about-min-max-normalization-in-python-b79592732b79">Min-Max Normalization </a> <br>
     * <p> A data is defined to be "high frequency" if its value is in range <br> [[visualizerMaxHeight] - [highFreqDelta] , [visualizerMaxHeight]] </p>
     */
    private fun minMaxNormalize(fftData: FloatArray, maxLimit: Int, minLimit: Int = 0) {
        min = Float.MAX_VALUE
        max = Float.MIN_VALUE
        for (value in fftData) {
            if (value > max) max = value
            if (value < min) min = value
        }
        if (max > visualizerMaxHeight) {
            for (idx in fftData.indices) {
                fftData[idx] = ((fftData[idx] - min) / (max - min)) * maxLimit + minLimit
                if (fftData[idx].isExclusive(
                        visualizerMaxHeight - highFreqDelta, visualizerMaxHeight
                    )
                ) {
                    handleHighFreqValue(idx)
                } else {
                    resetMapValue(idx)
                }
            }
        }
    }

    /**
     * Handle high frequency value to avoid low variability
     * If that data is in range [[visualizerMaxHeight] - [highFreqDelta] , [visualizerMaxHeight]]
     */
    private fun handleHighFreqValue(idx: Int) {
        try {
            if (frequencyMap.containsKey(idx)) {
                frequencyMap[idx] = frequencyMap[idx]!!.plus(1)
            } else {
                frequencyMap[idx] = 1
            }
            if (frequencyMap[idx]!! > 3) {
                frequencyMap[idx] = 0
                upperFFT[idx] =
                    (random.nextInt((visualizerMaxHeight - highFreqDelta) - highFreqDelta + 1) + highFreqDelta).toFloat()
            }
        } catch (e: Exception) {
            e.printStackTrace()
        }
    }

    /**
     * If the frequency value is not continue to return high frequency, reset it counter in [frequencyMap]
     */
    private fun resetMapValue(idx: Int) {
        if (frequencyMap.containsKey(idx) && frequencyMap[idx]!! > 0) {
            frequencyMap[idx] = 0
        }
    }

    private fun Float.isExclusive(start: Int, stop: Int): Boolean {
        return (this >= start && this <= stop)
    }

    private fun getShortest(): Float = Integer.min(currentWidth, currentHeight).toFloat()

    override fun setPaintColor(vararg color: Int) {
        if(color.isEmpty()) return
        this.paint.color = color[0]
        this.bottomLinePaint.color = color[0]
        if(color.size >= 2) this.spearPaint.color = color[1]
        else this.spearPaint.color = color[0]
        paint.alpha = PAINT_ALPHA
        bottomLinePaint.alpha = BOTTOM_PAINT_ALPHA
        spearPaint.alpha = SPEAR_PAINT_ALPHA
    }

    companion object {
        private const val TAG = "ParticleAnimation"
        private const val numberOfDot: Int = 100
        private const val drawSpearThreshold = 20F
        private const val pointRadius = 4f
        private const val visualizerColor = "#FFFFFF"
        private const val PAINT_ALPHA = 200
        private const val BOTTOM_PAINT_ALPHA = 175
        private const val SPEAR_PAINT_ALPHA = 30
        val upperPoints = Array(numberOfDot + 1) { EPointF() }
        val bottomPoints = Array(numberOfDot + 1) { EPointF() }
        val centerPoint = EPointF(0F, 0F)
    }
}