Extract core SVG element before rendering (#57)

Author: simonw

svg-render.html

@@ -237,12 +237,18 @@ <h2>Base64 Image Tag:</h2>
             downloadLink.style.display = 'none';
             fileSizeSpan.textContent = '';
 
-            // Find the <?xml tag and ignore everything before it
-            const xmlIndex = svgContent.indexOf('<?xml');
-            if (xmlIndex !== -1) {
-                svgContent = svgContent.substring(xmlIndex);
+            // Extract the SVG element, ignoring any surrounding content
+            const lowerContent = svgContent.toLowerCase();
+            const svgStart = lowerContent.indexOf('<svg');
+            const svgEnd = lowerContent.lastIndexOf('</svg>');
+
+            if (svgStart === -1 || svgEnd === -1) {
+                alert('Invalid SVG input');
+                return;
             }
 
+            svgContent = svgContent.slice(svgStart, svgEnd + '</svg>'.length);
+
             // Create a temporary SVG element
             const svgElement = new DOMParser().parseFromString(svgContent, 'image/svg+xml').documentElement;