kopia lustrzana https://github.com/vitorpamplona/amethyst
321 wiersze
9.3 KiB
Kotlin
321 wiersze
9.3 KiB
Kotlin
/**
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* Copyright (c) 2024 Vitor Pamplona
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
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* Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
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* AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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package com.vitorpamplona.amethyst.service
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import android.graphics.Bitmap
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import android.graphics.Color
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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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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 *
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// 2 * nBitmaps
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// the cache is enabled by default, it is recommended to disable it only when just a few images
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// are displayed
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private val cacheCosinesX = HashMap<Int, DoubleArray>()
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private val cacheCosinesY = HashMap<Int, DoubleArray>()
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/**
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* Clear calculations stored in memory cache. The cache is not big, but will increase when many
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* image sizes are used, if the app needs memory it is recommended to clear it.
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*/
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fun clearCache() {
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cacheCosinesX.clear()
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cacheCosinesY.clear()
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}
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/** Returns width/height */
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fun aspectRatio(blurHash: String?): Float? {
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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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return numCompX.toFloat() / numCompY.toFloat()
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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. By
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* default it is true.
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*/
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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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checkNotInMainThread()
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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 =
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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(
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str: String,
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from: Int = 0,
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to: Int = str.length,
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): 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(
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value: Int,
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maxAc: Float,
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): 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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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 = cosinesX.getCos(calculateCosX, i, numCompX, x, width)
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val cosY = 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] = Color.rgb(linearToSrgb(r), linearToSrgb(g), linearToSrgb(b))
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}
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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(
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calculate: Boolean,
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height: Int,
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numCompY: Int,
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) = when {
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calculate -> {
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DoubleArray(height * numCompY).also { cacheCosinesY[height * numCompY] = it }
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}
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else -> {
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cacheCosinesY[height * numCompY]!!
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}
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}
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private fun getArrayForCosinesX(
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calculate: Boolean,
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width: Int,
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numCompX: Int,
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) = when {
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calculate -> {
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DoubleArray(width * numCompX).also { cacheCosinesX[width * numCompX] = it }
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}
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else -> cacheCosinesX[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 =
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listOf(
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'0',
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'1',
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'2',
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'3',
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'4',
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'5',
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'6',
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'7',
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'8',
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'9',
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'A',
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'B',
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'C',
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'D',
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'E',
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'F',
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'G',
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'H',
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'I',
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'J',
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'K',
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'L',
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'M',
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'N',
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'O',
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'P',
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'Q',
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'R',
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'S',
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'T',
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'U',
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'V',
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'W',
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'X',
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'Y',
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'Z',
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'a',
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'b',
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'c',
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'd',
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'e',
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'f',
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'g',
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'h',
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'i',
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'j',
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'k',
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'l',
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'm',
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'n',
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'o',
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'p',
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'q',
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'r',
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's',
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't',
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'u',
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'v',
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'w',
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'x',
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'y',
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'z',
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'#',
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'$',
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'%',
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'*',
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'+',
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',',
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'-',
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'.',
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':',
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';',
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'=',
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'?',
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'@',
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'[',
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']',
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'^',
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'_',
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'{',
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'|',
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'}',
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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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