Remove custom jinc and replace it with SpecialFunctions.jinc (#77)

* Remove custom jinc and replace it with SpecialFunctions.jinc * Remove jinc file * Revert "Remove jinc file" This reverts commit 322429d. * Revert "Remove custom jinc and replace it with SpecialFunctions.jinc" This reverts commit f3b0e0f. * Revert to old convention but call SpecialFunctions * Update comment --------- Co-authored-by: Jeff Fessler <[email protected]>
JuliaImageRecon · Feb 3, 2023 · 3ce70f6 · 3ce70f6
1 parent 2399ad5
commit 3ce70f6
Showing 1 changed file with 5 additions and 6 deletions.
diff --git a/src/jinc.jl b/src/jinc.jl
@@ -4,7 +4,7 @@ jinc.jl
 
 export jinc
 
-using SpecialFunctions: besselj1
+import SpecialFunctions
 
 
 """
@@ -15,11 +15,10 @@ where `J1` is a Bessel function of the first kind.
 
 The argument `x` must be unitless.
 
-Return type is `promote_type(typeof(x), Float32)`.
+!!! note
+    `SpecialFunctions.jinc(0) = 1` whereas the convention here is `jinc(0) = π / 4`
+    which corresponds to the area of a disk of unit diameter.
 """
 function jinc(x::X) where {X <: Real}
-    T = promote_type(X, Float32)
-    if (x == 0) return convert(T, π/4) end
-    y = abs(x)
-    convert(T, besselj1(π*y) / (2*y))
+    X(π) / 4 * SpecialFunctions.jinc(x)
 end