--- a
+++ b/code/padarray.lua
@@ -0,0 +1,43 @@
+local function dimnarrow(x,sz,pad,dim)
+    local xn = x
+    for i=1,x:dim() do
+        if i > dim then
+            xn = xn:narrow(i,pad[i]+1,sz[i])
+        end
+    end
+    return xn
+end
+
+local function padzero(x,pad)
+    local sz = x:size()
+    for i=1,x:dim() do 
+      sz[i] = sz[i]+pad[i]*2 
+    end
+    local xx = x.new(sz):zero()
+    local xn = dimnarrow(xx,x:size(),pad,-1)
+    xn:copy(x)
+    return xx
+end
+
+local function padmirror(x,pad)
+    local xx = padzero(x,pad)
+    local sz  = xx:size()
+    for i=1,x:dim() do
+        local xxn = dimnarrow(xx,x:size(),pad,i)
+        for j=1,pad[i] do
+            xxn:select(i,j):copy(xxn:select(i,pad[i]*2-j+1))
+            xxn:select(i,sz[i]-j+1):copy(xxn:select(i,sz[i]-pad[i]*2+j))
+        end
+    end
+    return xx
+end
+
+function padarray(x,pad,padtype)
+-- Example usage:  img = padarray(img,{0, pady, padx},'zero')
+    if x:dim() ~= #pad then
+        error('number of dimensions of Input should match number of padding sizes')
+    end
+    if padtype == 'zero' then return padzero(x,pad) end
+    if padtype == 'mirror' then return padmirror(x,pad) end
+    error('unknown paddtype ' .. padtype)
+end