Got favicons better supported, can't get transparency right

Digging deeper, I don't think PHPGD supports 32bit bmp output which
complicates matters.

app/Uploads/FaviconHandler.php

@@ -28,6 +28,8 @@ public function saveForUploadedImage(UploadedFile $file): void
         $bmpData = $image->encode('bmp');
         $icoData = $this->bmpToIco($bmpData, 32, 32);
 
+//        file_put_contents(public_path('icon.bmp'), $bmpData);
+//        file_put_contents(public_path('icon-test.png'), $image->encode('png'));
         file_put_contents($targetPath, $icoData);
     }
 
@@ -54,6 +56,9 @@ protected function bmpToIco(string $bmpData, int $width, int $height): string
     {
         // Trim off the header of the bitmap file
         $rawBmpData = substr($bmpData, 14);
+        // Double the height in the "BITMAPINFOHEADER" since, when in an ICO file, half
+        // of the image data is expected to be a mask.
+        $rawBmpData[8] = hex2bin(dechex($height * 2));
 
         // ICO header
         $header = pack('v', 0x00); // Reserved. Must always be 0
@@ -66,17 +71,23 @@ protected function bmpToIco(string $bmpData, int $width, int $height): string
         $entry .= "\0"; // Color palette, typically 0
         $entry .= "\0"; // Reserved
 
+        // AND mask
+//        $pxCount = $width * $height;
+//        $pxMask = hex2bin('00000000');
+//        $mask = str_repeat($pxMask, $pxCount);
+        $mask = '';
+
         // Color planes, Appears to remain 1 for bmp image data
         $entry .= pack('v', 0x01);
         // Bits per pixel, can range from 1 to 32. From testing conversion
-        // via intervention from png typically provides this as 32.
-        $entry .= pack('v', 0x20);
+        // via intervention from png typically provides this as 24.
+        $entry .= pack('v', 0x18);
         // Size of the image data in bytes
-        $entry .= pack('V', strlen($rawBmpData));
+        $entry .= pack('V', strlen($rawBmpData) + strlen($mask));
         // Offset of the bmp data from file start
         $entry .= pack('V', strlen($header) + strlen($entry) + 4);
 
         // Join & return the combined parts of the ICO image data
-        return $header . $entry . $rawBmpData;
+        return $header . $entry . $rawBmpData . $mask;
     }
 }