From 701d39f7fb787860b79d1ee1f6b1e44217c2788c Mon Sep 17 00:00:00 2001
From: Andrew Cady <d@jerkface.net>
Date: Thu, 7 Jan 2021 17:53:53 -0500
Subject: marginate

---
 dot/local/bin/marginate | 39 ++++++++++++++++++++++++++++++---------
 1 file changed, 30 insertions(+), 9 deletions(-)

diff --git a/dot/local/bin/marginate b/dot/local/bin/marginate
index e62410c..b56e795 100755
--- a/dot/local/bin/marginate
+++ b/dot/local/bin/marginate
@@ -1,16 +1,37 @@
 #!/bin/sh
 
-margin=100
-aspect_ratio=177
+ratio_w=533
+ratio_h=300
 
-extent=$((margin * aspect_ratio / 100))%x${margin}%
-options="-gravity center -extent $extent"
+sentinel=margins
+
+choose_extent()
+{
+    local ratio_w="$1" ratio_h="$2" input="$3"
+
+    identify -format '%w %h\n' "$input" | {
+
+        read w h || return
+
+        w_prime=$((h * ratio_w / ratio_h))
+        if [ "$w_prime" -gt "$w" ]
+        then
+            w=$w_prime
+        else
+            h=$((w * ratio_h / ratio_w))
+        fi
+        echo ${w}x${h}
+    }
+}
 
 for input
 do
-  case "$input" in
-       *.*) output=${input%.*}.margins.${input##*.} ;;
-       *)   output=$input.margins.png ;;
-  esac
-  convert "$input" $options "$output"
+    case "$input" in
+        *.*) output=${input%.*}.$sentinel.${input##*.} ;;
+        *)   output=$input.$sentinel.png ;;
+    esac
+    [ -f "$input" ] || continue
+    extent=$(choose_extent $ratio_w $ratio_h "$input") || continue
+
+    convert "$input" -gravity center -extent "$extent" "$output"
 done
-- 
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