From 5993ea8f6fd4316aee313e1e6fdae2dc7fbab5df Mon Sep 17 00:00:00 2001
From: Akshay Nair <phenax5@gmail.com>
Date: Wed, 3 Jun 2026 12:49:35 +0530
Subject: Add circle example

---
 examples/circle.sql   | 18 ++++++++++++++++++
 examples/gradient.sql |  8 ++++----
 justfile              |  3 +--
 setup.sql             |  7 +++++++
 4 files changed, 30 insertions(+), 6 deletions(-)
 create mode 100644 examples/circle.sql

diff --git a/examples/circle.sql b/examples/circle.sql
new file mode 100644
index 0000000..46874cc
--- /dev/null
+++ b/examples/circle.sql
@@ -0,0 +1,18 @@
+DELETE FROM images WHERE id = 'circle';
+INSERT INTO images (id, width, height) VALUES ('circle', 200, 200) RETURNING id;
+
+WITH RECURSIVE
+  image AS (SELECT * FROM images WHERE id = 'circle'),
+  circle AS (SELECT width/2 AS cx, height/2 AS cy, 80 AS radius FROM image),
+  horizontal(x) AS
+    (SELECT width FROM image UNION ALL SELECT x - 1 FROM horizontal WHERE x > 1),
+  vertical(y) AS
+    (SELECT height FROM image UNION ALL SELECT y - 1 FROM vertical WHERE y > 1),
+  _pixels(x, y, r, g, b) AS (SELECT
+    x, y,
+    150,
+    255 * MAX(0, MIN(1, (SELECT POW(x - cx, 2) + POW(y - cy, 2) - POW(radius, 2) FROM circle))),
+    150
+    FROM vertical, horizontal
+  )
+INSERT INTO pixels (image_id, x, y, r, g, b) SELECT 'circle', x, y, r, g, b FROM _pixels;
diff --git a/examples/gradient.sql b/examples/gradient.sql
index 9aa9010..f04cdad 100644
--- a/examples/gradient.sql
+++ b/examples/gradient.sql
@@ -1,12 +1,12 @@
+DELETE FROM images WHERE id = 'gradient';
 INSERT INTO images (id, width, height) VALUES ('gradient', 200, 200) RETURNING id;
 
 WITH RECURSIVE
-  width AS (SELECT width FROM images WHERE id = 'gradient'),
-  height AS (SELECT height FROM images WHERE id = 'gradient'),
+  image AS (SELECT * FROM images WHERE id = 'gradient'),
   horizontal(x) AS
-    (SELECT * FROM width UNION ALL SELECT x - 1 FROM horizontal WHERE x > 1),
+    (SELECT width FROM image UNION ALL SELECT x - 1 FROM horizontal WHERE x > 1),
   vertical(y) AS
-    (SELECT * FROM height UNION ALL SELECT y - 1 FROM vertical WHERE y > 1),
+    (SELECT height FROM image UNION ALL SELECT y - 1 FROM vertical WHERE y > 1),
   _pixels(x, y, r, g, b) AS
     (SELECT x, y, mod(x, 255), mod(y, 255), 100 FROM vertical, horizontal)
 INSERT INTO pixels (image_id, x, y, r, g, b) SELECT 'gradient', x, y, r, g, b FROM _pixels;
diff --git a/justfile b/justfile
index b67c6f8..be55afb 100644
--- a/justfile
+++ b/justfile
@@ -12,8 +12,7 @@ image file *args:
   just show-image "$image_id"
 
 show-image image_id:
-  #!/usr/bin/env sh
-  echo "Displaying $image_id" 1>&2
+  echo "Displaying {{image_id}}" 1>&2
   ./image.sh {{image_id}} | magick display -
 
 repl *args:
diff --git a/setup.sql b/setup.sql
index d5d8ce2..7b6732e 100644
--- a/setup.sql
+++ b/setup.sql
@@ -18,3 +18,10 @@ CREATE TABLE pixels (
   FOREIGN KEY(image_id) REFERENCES images(id),
   UNIQUE(image_id, x, y)
 );
+
+CREATE TRIGGER delete_pixels_when_image_deleted
+AFTER DELETE ON images
+WHEN (SELECT COUNT(*) FROM images WHERE id = OLD.id) = 0
+BEGIN
+  DELETE FROM pixels WHERE image_id = OLD.id;
+END;
-- 
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