Mercurial > cgi-bin > hgweb.cgi > SimpleResizer

changeset 8:6ae738b8a814 memo

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Memoize. Only modest improvement results.
author David Barts <n5jrn@me.com>
date Wed, 17 Feb 2021 07:43:50 -0800
parents e8059b166de1
children 5626557ac542
files app/src/main/java/com/bartsent/simpleresizer/lib/LanczosKernel.kt
diffstat 1 files changed, 10 insertions(+), 3 deletions(-) [+]
line wrap: on
line diff
--- a/app/src/main/java/com/bartsent/simpleresizer/lib/LanczosKernel.kt	Tue Feb 16 17:29:52 2021 -0800
+++ b/app/src/main/java/com/bartsent/simpleresizer/lib/LanczosKernel.kt	Wed Feb 17 07:43:50 2021 -0800
@@ -6,12 +6,19 @@
 
 object LanczosKernel: ScalingKernel {
     override val size = 3.0
+    private val memory = HashMap<Double, Double>()
+    init {
+        memory.put(0.0, 1.0)
+    }
 
     private fun sinc(x: Double): Double {
-        if (x == 0.0)
-            return 1.0
+        val remembered = memory.get(x)
+        if (remembered != null)
+            return remembered
         val pix = PI * x
-        return sin(pix) / pix
+        val calculated = sin(pix) / pix
+        memory.put(x, calculated)
+        return calculated
     }
 
     override fun weight(x: Double): Double =