Fix β₀ < 0 issue (#50)

* Fix beta<0 issue

* v0.4.1

* Use minimum

Author: JeffFessler

Project.toml

@@ -1,7 +1,7 @@
 name = "Sinograms"
 uuid = "02a14def-c6e6-4ab0-b2df-0ab64bc8cdd7"
 authors = ["fessler <[email protected]>"]
-version = "0.4.0"
+version = "0.4.1"
 
 [deps]
 FFTW = "7a1cc6ca-52ef-59f5-83cd-3a7055c09341"

src/fbp/parker.jl

@@ -82,7 +82,8 @@ function parker_weight_fan_short(
         @warn("orbit $orbit exceeds short scan $orbit_short by %g views")
     #   (orbit - orbit_short) / rad2deg(ar[begin+1] - ar[begin]))
 
-    bet = ar .- ar[begin] # trick: force 0 start, so this ignores orbit_start!
+    bet = ar .- minimum(ar) # trick: force 0 start, so this ignores orbit_start!
+    bet = max.(bet, zero(eltype(bet))) # fix for issue #49
     (gg, bb) = ndgrid(gam, bet)
 
     fun = (x) -> sin(π/2 * x)^2 # smooth out [0,1] ramp

src/fbp3/cbct-back.jl

@@ -136,7 +136,7 @@ function cbct_back_fan!(
             proj, sinβ, cosβ, dt / ds, ws, wt,
 #           offset_source / ds,
             dsd / ds, dso / ds, is_arc,
-            xc_ds[c[1]], yc_ds[c[2]], zc_ds[c[3]]
+            xc_ds[c[1]], yc_ds[c[2]], zc_ds[c[3]],
         )
     end