BtrArt1

MainActivity.kt

package com.example.btrart1

import android.animation.TimeAnimator
import android.os.Bundle
import android.view.Window
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        //タイトルバーを消す
        supportRequestWindowFeature(Window.FEATURE_NO_TITLE)
        //
        val myView=MyView(this)
        setContentView(myView)
        //アニメーションの設定
        val anim =TimeAnimator()
        val fpm=(1000/60).toLong()
        anim.duration=fpm
        anim.setTimeListener { _, _, _ ->
            myView.invalidate()
            myView.update()
        }
        anim.start()
    }

}

MovieToBmp.kt

package com.example.btrart1

import android.content.Context
import android.net.Uri
import android.media.MediaMetadataRetriever
import android.graphics.Bitmap
import android.graphics.Color
import android.graphics.Matrix
import androidx.core.graphics.blue
import androidx.core.graphics.green
import androidx.core.graphics.red

//動画から画像を切り出す
class MovieToBmp {
    var bmps= Array(4) { Array<Bitmap?>(360) { null } }
    var initialized=false
    //
    fun set(context: Context){
        val moviePath = Uri.parse("android.resource://"+context.packageName+"/"+R.raw.bocchi)
        //val videoView=VideoView(context)
        val ret=MediaMetadataRetriever()
        //videoView.setVideoURI(moviePath)
        ret.setDataSource(context,moviePath)
        //var count = ret.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION)!!.toInt()
        val rate=0.4
        //
        for (i in 0 until 4) {
            val j= arrayOf(2,4,5,7)[i]
            var bmp=ret.getFrameAtTime(
                (j * 1000 * 1000).toLong(),
                MediaMetadataRetriever.OPTION_CLOSEST)
            //リサイズ
            bmp=Bitmap.createScaledBitmap(
                //切り取り
                Bitmap.createBitmap(
                    bmp!!,
                    bmp.width-bmp.height,
                    0,
                    bmp.height,
                    bmp.height),
                (bmp.height*rate).toInt(),
                (bmp.height*rate).toInt(),
                true
            ).copy(Bitmap.Config.ARGB_8888,true)
            //
            bmp.setHasAlpha(true)
            for(raw in 0 until bmp.width){
                for(col in 0 until bmp.height){
                    val px=bmp.getPixel(raw,col)
                    if(px.green>256-96 && px.red<96 && px.blue <96){
                        bmp.setPixel(raw,col, Color.TRANSPARENT)
                    }
                }
            }
            //
            bmps[i][0]=bmp
        }
        //
        ret.release()
    }

    fun createRotBmp(){
        for(i in 0 until 4)
            for(j in 0 until 360){
                if (bmps[i][j] == null) {
                    val bmp=bmps[i][0]
                    val m=Matrix()
                    m.setRotate(j.toFloat())//Degree
                    bmps[i][j] = Bitmap.createBitmap(bmp!!,0,0, bmp.width, bmp.height,m,true)
                }
            }
        //
    }
    //
    fun get(kind:Int,deg:Int): Bitmap? {
        return if (initialized) {
            if (bmps[kind % 4][deg % 360] == null) {
                val bmp=bmps[kind%4][0]
                val m=Matrix()
                m.setRotate(deg.toFloat())//Degree
                bmps[kind % 4][deg % 360] = Bitmap.createBitmap(bmp!!,0,0, bmp.width, bmp.height,m,true)
            }
            bmps[kind % 4][deg % 360]
        }
        else {
            null
        }
    }

}

MyView.kt

package com.example.btrart1

import android.annotation.SuppressLint
import android.content.Context
import android.graphics.*
import android.os.Build
import android.view.View
import androidx.annotation.RequiresApi
import androidx.core.graphics.createBitmap
import kotlin.math.*
import kotlin.random.Random

//描画本体
class MyView(context: Context): View(context){
    //
    private val paint: Paint = Paint()
    //
    private var m2b=MovieToBmp()
    //
    private val starsNum=40
    private var stars= arrayListOf<Star>()
    //
    init {
        //
        Thread{
            m2b.set(context)
            m2b.createRotBmp()
            m2b.initialized=true
        }.start()
        //
        for(i in 0 until starsNum){
            stars.add(Star(paint,m2b))
        }
        //
    }

    //描画関数
    @RequiresApi(Build.VERSION_CODES.Q)
    @SuppressLint("DrawAllocation")
    override fun onDraw(canvas: Canvas){
        val bmp= createBitmap(width,height,Bitmap.Config.ARGB_8888)
        val cbmp=Canvas()
        //
        cbmp.setBitmap(bmp)
        cbmp.drawColor(Color.TRANSPARENT,PorterDuff.Mode.CLEAR)
        //
        draw2(cbmp)
        //背景塗りつぶし
        canvas.drawColor(Color.WHITE)
        canvas.drawBitmap(bmp,0F,0F,null)
        //文字
        //paint.color=Color.DKGRAY
        //paint.style=Paint.Style.FILL_AND_STROKE
        //paint.strokeWidth=5F
        //paint.textSize=100F
        //canvas.drawText("bocchi the rock", 0F, 100F,paint)
    }

    //描画する
    @RequiresApi(Build.VERSION_CODES.Q)
    private fun draw2(canvas: Canvas){
        //
        paint.style=Paint.Style.FILL_AND_STROKE
        paint.xfermode = PorterDuffXfermode(PorterDuff.Mode.LIGHTEN)
        for (i in 0 until starsNum)
            for (j in i + 1 until starsNum)
                for (k in j + 1 until starsNum) {
                    val s = stars[i]
                    val t = stars[j]
                    val u = stars[k]
                    if (s.kind == t.kind && t.kind == u.kind) {
                        if (s.distance(t) < 1000F && s.distance(u) < 1000F && t.distance(u) < 1000F) {
                            paint.color = s.col and 0x0FFFFFFF
                            val path = Path()
                            path.moveTo(s.x, s.y)
                            path.lineTo(t.x, t.y)
                            path.lineTo(u.x, u.y)
                            //path.close()//FILLのときは省略可
                            canvas.drawPath(path, paint)
                        }
                    }
                }
        //
        paint.xfermode=null
        //
        //paint.style=Paint.Style.FILL_AND_STROKE
        /*paint.color=0x8FFFFFFF.toInt()//Alphaは反映されるので注意
        for(i in 0 until starsNum)
            for(j in i+1 until starsNum){
                val s=stars[i]
                val t=stars[j]
                if(s.kind==t.kind) continue
                //
                if(s.distance(t)<600F){
                    //グラデーション
                    val gradient=LinearGradient(s.x,s.y,t.x,t.y,
                        s.col,t.col,Shader.TileMode.CLAMP)
                    paint.shader = gradient
                    //
                    val w=1-cos(s.distance(t) / 600 * PI / 2)//0~2
                    paint.strokeWidth=(5.0+4*w*w).toFloat()
                    //canvas.drawLine(s.x,s.y,t.x,t.y,paint)
                }
            }
        paint.shader = null
        */
        //
        for(s in stars){
            s.drawCircle(canvas)
            s.draw2(canvas)
        }
    }

    //値更新
    fun update(){
        //
        for (s in stars){
            s.update(this)
        }
    }

    //
    class Star(val paint:Paint, val m2b:MovieToBmp){
        //
        var radius=Random.nextDouble(150.0,500.0)
        var cx=Random.nextDouble(-900.0,900.0)
        var cy=Random.nextDouble(-900.0,900.0)
        var direction= if(Random.nextBoolean())1.0 else -1.0
        var radian=Random.nextDouble(2*PI)
        //
        var cr=150F
        var deg=Random.nextInt(360)
        var degd=if(Random.nextBoolean())1 else -1
        //
        var x=0F
        var y=0F
        //
        val kind= Random.nextInt(4)
        val cols=arrayOf(Color.MAGENTA,Color.YELLOW,Color.CYAN,Color.RED)
        var col=cols[kind]
        //
        var bmp:Bitmap?=null
        //
        fun draw2(canvas:Canvas){
            if(bmp!=null){
                canvas.drawBitmap(bmp!!, x - (bmp!!.width/2), y - (bmp!!.height/2), null)
            }
        }

        @RequiresApi(Build.VERSION_CODES.Q)
        fun drawCircle(canvas:Canvas){
            //
            paint.color=col and 0x4FFFFFFF
            paint.style= Paint.Style.FILL
            paint.xfermode = PorterDuffXfermode(PorterDuff.Mode.LIGHTEN)
            //
            canvas.drawCircle(x,y,cr,paint)
        }
        //
        fun update(layout:View){
            radian+=direction*2*PI*(1/radius)
            deg=if(deg+degd>0)(deg+degd)%360 else 360+degd
            //
            x=(cos(radian)*radius+cx).toFloat()+layout.width/2
            y= (sin(radian)*radius+cy).toFloat()+layout.height/2
            //
            if(m2b.initialized){
                bmp=m2b.get(kind,deg)
            }
        }
        //
        fun distance(s:Star): Float {
            val vx=x-s.x
            val vy=y-s.y
            return sqrt(vx*vx+vy*vy)
        }
    }
    
}