218 lines
7.8 KiB
Kotlin
218 lines
7.8 KiB
Kotlin
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package com.aiosman.riderpro.utils
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import android.graphics.Bitmap
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import android.graphics.Color
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import androidx.collection.SparseArrayCompat
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import kotlinx.coroutines.CoroutineScope
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import kotlinx.coroutines.Deferred
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import kotlinx.coroutines.Dispatchers
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import kotlinx.coroutines.SupervisorJob
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import kotlinx.coroutines.async
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import kotlinx.coroutines.launch
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import kotlinx.coroutines.runBlocking
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import kotlin.math.cos
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import kotlin.math.pow
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import kotlin.math.withSign
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internal object BlurHashDecoder {
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// cache Math.cos() calculations to improve performance.
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// The number of calculations can be huge for many bitmaps: width * height * numCompX * numCompY * 2 * nBitmaps
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// the cache is enabled by default, it is recommended to disable it only when just a few images are displayed
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private val cacheCosinesX = SparseArrayCompat<DoubleArray>()
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private val cacheCosinesY = SparseArrayCompat<DoubleArray>()
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/**
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* Clear calculations stored in memory cache.
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* The cache is not big, but will increase when many image sizes are used,
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* if the app needs memory it is recommended to clear it.
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*/
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private fun clearCache() {
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cacheCosinesX.clear()
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cacheCosinesY.clear()
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}
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/**
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* Decode a blur hash into a new bitmap.
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*
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* @param useCache use in memory cache for the calculated math, reused by images with same size.
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* if the cache does not exist yet it will be created and populated with new calculations.
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* By default it is true.
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*/
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@Suppress("ReturnCount")
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internal fun decode(
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blurHash: String?,
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width: Int,
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height: Int,
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punch: Float = 1f,
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useCache: Boolean = true
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): Bitmap? {
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if (blurHash == null || blurHash.length < 6) {
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return null
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}
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val numCompEnc = decode83(blurHash, 0, 1)
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val numCompX = (numCompEnc % 9) + 1
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val numCompY = (numCompEnc / 9) + 1
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if (blurHash.length != 4 + 2 * numCompX * numCompY) {
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return null
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}
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val maxAcEnc = decode83(blurHash, 1, 2)
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val maxAc = (maxAcEnc + 1) / 166f
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val colors = Array(numCompX * numCompY) { i ->
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if (i == 0) {
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val colorEnc = decode83(blurHash, 2, 6)
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decodeDc(colorEnc)
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} else {
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val from = 4 + i * 2
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val colorEnc = decode83(blurHash, from, from + 2)
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decodeAc(colorEnc, maxAc * punch)
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}
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}
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return composeBitmap(width, height, numCompX, numCompY, colors, useCache)
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}
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private fun decode83(str: String, from: Int = 0, to: Int = str.length): Int {
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var result = 0
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for (i in from until to) {
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val index = charMap[str[i]] ?: -1
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if (index != -1) {
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result = result * 83 + index
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}
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}
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return result
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}
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private fun decodeDc(colorEnc: Int): FloatArray {
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val r = colorEnc shr 16
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val g = (colorEnc shr 8) and 255
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val b = colorEnc and 255
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return floatArrayOf(srgbToLinear(r), srgbToLinear(g), srgbToLinear(b))
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}
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private fun srgbToLinear(colorEnc: Int): Float {
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val v = colorEnc / 255f
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return if (v <= 0.04045f) {
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(v / 12.92f)
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} else {
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((v + 0.055f) / 1.055f).pow(2.4f)
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}
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}
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private fun decodeAc(value: Int, maxAc: Float): FloatArray {
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val r = value / (19 * 19)
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val g = (value / 19) % 19
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val b = value % 19
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return floatArrayOf(
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signedPow2((r - 9) / 9.0f) * maxAc,
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signedPow2((g - 9) / 9.0f) * maxAc,
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signedPow2((b - 9) / 9.0f) * maxAc
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)
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}
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private fun signedPow2(value: Float) = value.pow(2f).withSign(value)
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private fun composeBitmap(
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width: Int,
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height: Int,
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numCompX: Int,
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numCompY: Int,
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colors: Array<FloatArray>,
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useCache: Boolean
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): Bitmap {
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// use an array for better performance when writing pixel colors
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val imageArray = IntArray(width * height)
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val calculateCosX = !useCache || !cacheCosinesX.containsKey(width * numCompX)
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val cosinesX = getArrayForCosinesX(calculateCosX, width, numCompX)
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val calculateCosY = !useCache || !cacheCosinesY.containsKey(height * numCompY)
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val cosinesY = getArrayForCosinesY(calculateCosY, height, numCompY)
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runBlocking {
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CoroutineScope(SupervisorJob() + Dispatchers.IO).launch {
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val tasks = ArrayList<Deferred<Unit>>()
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tasks.add(
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async {
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for (y in 0 until height) {
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for (x in 0 until width) {
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var r = 0f
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var g = 0f
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var b = 0f
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for (j in 0 until numCompY) {
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for (i in 0 until numCompX) {
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val cosX =
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cosinesX.getCos(calculateCosX, i, numCompX, x, width)
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val cosY =
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cosinesY.getCos(calculateCosY, j, numCompY, y, height)
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val basis = (cosX * cosY).toFloat()
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val color = colors[j * numCompX + i]
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r += color[0] * basis
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g += color[1] * basis
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b += color[2] * basis
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}
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}
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imageArray[x + width * y] =
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Color.rgb(linearToSrgb(r), linearToSrgb(g), linearToSrgb(b))
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}
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}
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return@async
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}
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)
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tasks.forEach { it.await() }
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}.join()
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}
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return Bitmap.createBitmap(imageArray, width, height, Bitmap.Config.ARGB_8888)
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}
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private fun getArrayForCosinesY(calculate: Boolean, height: Int, numCompY: Int) = when {
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calculate -> {
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DoubleArray(height * numCompY).also {
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cacheCosinesY.put(height * numCompY, it)
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}
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}
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else -> {
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cacheCosinesY.get(height * numCompY)!!
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}
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}
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private fun getArrayForCosinesX(calculate: Boolean, width: Int, numCompX: Int) = when {
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calculate -> {
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DoubleArray(width * numCompX).also {
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cacheCosinesX.put(width * numCompX, it)
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}
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}
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else -> cacheCosinesX.get(width * numCompX)!!
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}
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private fun DoubleArray.getCos(
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calculate: Boolean,
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x: Int,
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numComp: Int,
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y: Int,
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size: Int
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): Double {
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if (calculate) {
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this[x + numComp * y] = cos(Math.PI * y * x / size)
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}
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return this[x + numComp * y]
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}
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private fun linearToSrgb(value: Float): Int {
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val v = value.coerceIn(0f, 1f)
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return if (v <= 0.0031308f) {
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(v * 12.92f * 255f + 0.5f).toInt()
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} else {
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((1.055f * v.pow(1 / 2.4f) - 0.055f) * 255 + 0.5f).toInt()
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}
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}
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private val charMap = listOf(
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'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
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'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
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'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
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'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '#', '$', '%', '*', '+', ',',
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'-', '.', ':', ';', '=', '?', '@', '[', ']', '^', '_', '{', '|', '}', '~'
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)
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.mapIndexed { i, c -> c to i }
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.toMap()
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}
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