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annotate app/src/main/java/com/bartsent/simpleresizer/lib/LanczosKernel.kt @ 13:b1605be35bcc memo.oo

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Dumping Bitmap yields 2x improvement!
author David Barts <n5jrn@me.com>
date Thu, 18 Feb 2021 14:15:26 -0800
parents 678adef4774f
children 86740f593b6c
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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 import kotlin.math.PI
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4 import kotlin.math.abs
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5 import kotlin.math.sin
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b1605be35bcc Dumping Bitmap yields 2x improvement!
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7 class LanczosKernel: ScalingKernel {
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8 override val size = 3.0
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9 private val memory = HashMap<Double, Double>()
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10 init {
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11 memory.put(0.0, 1.0)
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12 }
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14 private fun sinc(x: Double): Double {
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678adef4774f Move more stuff into worker threads.
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15 val remembered = memory[x]
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16 if (remembered != null)
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17 return remembered
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18 val pix = PI * x
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19 val calculated = sin(pix) / pix
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20 memory[x] = calculated
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21 return calculated
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22 }
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23
e8059b166de1 Lanczos works, but is painfully slow.
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24 override fun weight(x: Double): Double =
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25 if (abs(x) < size) sinc(x) * sinc(x/size) else 0.0
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26 }