diff --git a/Tupfile.lua b/Tupfile.lua
index 4bc29ef8..faca33a4 100644
--- a/Tupfile.lua
+++ b/Tupfile.lua
@@ -64,3 +64,34 @@ local files =
 fbsprite(files, "build/smogon/fbsprites/xy/%B.png")
 twittersprite(files, "build/smogon/twittersprites/xy/%B.png")
 
+-- Trainers
+
+function padtrainer(input, output)
+    return "convert " .. input .. " -background transparent -gravity center -extent 80x80 " .. output
+end
+
+-- TODO: move some of these to util, when we figure out the precise abstractions desired
+
+function compresspng(filename, opts)
+    local cmds = {}
+    if opts.optipng then
+        cmds += "optipng -q " .. opts.optipng .. " " .. filename
+    end
+    if opts.advpng then
+        cmds += "advpng -q " .. opts.advpng .. " " .. filename
+    end
+    return cmds
+end
+
+function makecmd(cmds)
+    return table.concat(flatten(cmds), " && ")
+end
+
+tup.foreach_rule(
+    {"src/canonical/trainers/*"},
+    "^ pad trainer %f^ " .. makecmd{padtrainer("%f", "%o"), compresspng("%f",  {})},
+    {"build/padded-trainers/canonical/%b"}
+)
+
+
+
diff --git a/util/lua-ext.lua b/util/lua-ext.lua
index 8668a4ca..f6d25a43 100644
--- a/util/lua-ext.lua
+++ b/util/lua-ext.lua
@@ -19,3 +19,21 @@ function astable(table)
         return {}
     end
 end
+
+-- Adapted from premake
+function flatten(arr)
+    local result = { }
+    
+    local function flatten(arr)
+        for v in iter(arr) do
+            if type(v) == "table" then
+                flatten(v)
+            else
+                table.insert(result, v)
+            end
+        end
+    end
+    
+    flatten(arr)
+    return result
+end