Adjust watermark permissions and transparency

app/Support/ImageHelper.php

@@ -178,10 +178,13 @@ class ImageHelper
             $y = max(0, min($srcH - $targetH, $y + $offsetY));
 
             $opacity = max(0.0, min(1.0, (float) ($config['opacity'] ?? 0.25)));
-            $mergeOpacity = (int) round($opacity * 100); // imagecopymerge uses 0-100
+
+            if ($opacity < 1.0) {
+                self::applyOpacity($resized, $opacity);
+            }
 
             imagealphablending($src, true);
-            imagecopymerge($src, $resized, $x, $y, 0, 0, $targetW, $targetH, $mergeOpacity);
+            imagecopy($src, $resized, $x, $y, 0, 0, $targetW, $targetH);
             imagedestroy($resized);
 
             // Overwrite original (respect mime: always JPEG for compatibility)
@@ -210,4 +213,34 @@ class ImageHelper
 
         return $applied ? $destPath : null;
     }
+
+    /**
+     * @param  \GdImage|resource  $image
+     */
+    private static function applyOpacity($image, float $opacity): void
+    {
+        $width = imagesx($image);
+        $height = imagesy($image);
+
+        if ($width <= 0 || $height <= 0) {
+            return;
+        }
+
+        imagealphablending($image, false);
+        imagesavealpha($image, true);
+
+        for ($x = 0; $x < $width; $x++) {
+            for ($y = 0; $y < $height; $y++) {
+                $rgba = imagecolorat($image, $x, $y);
+                $alpha = ($rgba >> 24) & 0x7F;
+                $red = ($rgba >> 16) & 0xFF;
+                $green = ($rgba >> 8) & 0xFF;
+                $blue = $rgba & 0xFF;
+
+                $adjustedAlpha = (int) round(127 - (127 - $alpha) * $opacity);
+                $color = imagecolorallocatealpha($image, $red, $green, $blue, max(0, min(127, $adjustedAlpha)));
+                imagesetpixel($image, $x, $y, $color);
+            }
+        }
+    }
 }