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annotate app/src/main/java/com/bartsent/simpleresizer/lib/LanczosKernel.kt @ 35:6607f675a5f7

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Add licensing.
author David Barts <n5jrn@me.com>
date Thu, 11 Mar 2021 22:41:48 -0800
parents 86740f593b6c
children
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e8059b166de1 Lanczos works, but is painfully slow.
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1 package com.bartsent.simpleresizer.lib
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3 /*
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4 * Some code in this file has been adapted from: https://github.com/disintegration/imaging/ .
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5 */
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7 import kotlin.math.PI
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8 import kotlin.math.abs
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9 import kotlin.math.sin
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11 class LanczosKernel: ScalingKernel {
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12 override val size = 3.0
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13 private val memory = HashMap<Double, Double>()
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15 private fun sinc(x: Double): Double {
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16 if (x == 0.0)
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17 return 1.0
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18 val pix = PI * x
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19 return sin(pix) / pix
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20 }
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22 override fun weight(x: Double): Double {
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23 if (abs(x) >= size)
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24 return 0.0
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25 val remembered = memory[x]
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26 if (remembered != null)
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27 return remembered
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28 val calculated = sinc(x) * sinc(x/size)
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29 memory[x] = calculated
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30 return calculated
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31 }
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32 }