fix：优化图片清晰度

js/script.js

@@ -1778,6 +1778,13 @@
         document.body.appendChild(menu);
     }
 
+    // 从 blob 显示预览
+    function showPreviewFromBlob(blob) {
+        console.log('预览图片大小:', (blob.size / 1024).toFixed(2), 'KB');
+        const dataUrl = URL.createObjectURL(blob);
+        showPreviewModal(dataUrl, blob);
+    }
+
     // 显示预览
     async function showPreview() {
         const canvas = await generateCanvas();
@@ -1787,6 +1794,11 @@
         const blob = await new Promise(resolve => canvas.toBlob(resolve, 'image/png', 1.0));
         console.log('预览图片大小:', (blob.size / 1024).toFixed(2), 'KB');
         const dataUrl = URL.createObjectURL(blob);
+        showPreviewModal(dataUrl, blob);
+    }
+
+    // 显示预览弹窗
+    function showPreviewModal(dataUrl, blob) {
 
         const tipOverlay = document.createElement('div');
         tipOverlay.id = 'previewTip';
@@ -1806,7 +1818,7 @@
         `;
 
         const tipText = document.createElement('p');
-        tipText.textContent = '长按图片保存到相册';
+        tipText.innerHTML = '长按图片保存到相册<br><span style="font-size:14px;opacity:0.8">（预览已缩放，实际保存为高清原图）</span>';
         tipText.style.cssText = `
             color: #fff;
             font-size: 18px;
@@ -1846,7 +1858,7 @@
         `;
         saveBtn.onclick = async () => {
             tipOverlay.remove();
-            await saveImageToGallery(dataUrl);
+            await saveImageToGallery(dataUrl, blob);
         };
 
         const closeBtn = document.createElement('button');
@@ -1871,13 +1883,17 @@
     }
 
     // 保存图片到相册
-    async function saveImageToGallery(dataUrl) {
+    async function saveImageToGallery(dataUrl, blob) {
         const filename = '邀请函_' + Date.now() + '.png';
         
+        // 如果没有传入 blob，尝试从 window._lastExportBlob 获取
+        if (!blob && window._lastExportBlob) {
+            blob = window._lastExportBlob;
+        }
+        
         // 尝试使用 File System Access API (Android/Chrome)
         if ('showSaveFilePicker' in window) {
             try {
-                const blob = await (await fetch(dataUrl)).blob();
                 const handle = await window.showSaveFilePicker({
                     suggestedName: filename,
                     types: [{
@@ -1898,7 +1914,6 @@
         // 尝试使用 Web Share API (iOS Safari)
         if (navigator.share && navigator.canShare) {
             try {
-                const blob = await (await fetch(dataUrl)).blob();
                 const file = new File([blob], filename, { type: 'image/png' });
                 
                 if (navigator.canShare({ files: [file] })) {
@@ -2248,6 +2263,9 @@
         const dataUrl = URL.createObjectURL(blob);
         const filename = '邀请函_' + Date.now() + '.png';
         
+        // 保存 blob 供后续使用
+        window._lastExportBlob = blob;
+
         const tipOverlay = document.createElement('div');
         tipOverlay.id = 'mobileSaveTip';
         tipOverlay.style.cssText = `
@@ -2342,7 +2360,7 @@
         `;
         previewBtn.onclick = () => {
             tipOverlay.remove();
-            showPreview();
+            showPreviewFromBlob(blob);
         };
 
         // 插入到标题后面