improve font sizing

src/lib/generate-og-image.tsx

@@ -14,41 +14,73 @@ function loadDataUrl(relPath: string, mimeType: string): string {
   return `data:${mimeType};base64,${base64Data}`;
 }
 
+/**
+ * A heuristic for choosing a font size to fill a box (assuming perfectly even line wrapping)
+ * @returns a size in pixels to roughly fill the box
+ */
+function maximizeFontSize({
+  text,
+  width,
+  height,
+}: {
+  text: string;
+  width: number;
+  height: number;
+}): number {
+  let lines = 1;
+  let size = Math.min(width / text.length, height);
+  while (size * (lines + 1) < height) {
+    lines += 1;
+    size = Math.min(width / (text.length / lines), height);
+  }
+  return size;
+}
+
 export async function generateOgImage({
   title,
 }: {
   title: string;
 }): Promise<ImageResponse> {
+  const width = 1200;
+  const height = 630;
+  const titleFontSize = `${maximizeFontSize({
+    text: title,
+    width,
+    height: height / 2,
+  })}px`;
+
   return new ImageResponse(
     (
       <div style={{display: 'flex'}}>
         <img
           src={loadDataUrl('og-background.png', 'image/png')}
           alt=""
-          width={1200}
-          height={630}
+          width={width}
+          height={height}
         />
         <div
           style={{
             position: 'absolute',
-            top: '0%',
+            top: '50%',
             left: '0%',
             width: '100%',
-            height: '100%',
-            paddingLeft: '2rem',
-            paddingBottom: '2rem',
+            height: '50%',
+            padding: '2rem',
+            paddingBottom: '4rem',
             display: 'flex',
-            alignItems: 'flex-end',
+            alignItems: 'center',
             justifyContent: 'flex-start',
             color: '#fff2dc',
           }}
         >
           <div
             style={{
               fontFamily: 'font-serif',
-              fontSize: '7rem',
+              fontSize: titleFontSize,
               // @ts-expect-error
               textWrap: 'balance',
+              lineHeight: '1.0',
+              wordBreak: 'break-word',
             }}
           >
             {title}
@@ -57,8 +89,8 @@ export async function generateOgImage({
       </div>
     ),
     {
-      width: 1200,
-      height: 630,
+      width,
+      height,
       fonts: [
         {
           name: 'font-serif',