diff --git a/app/src/main/java/com/inspection/camera/util/ImageProcessor.kt b/app/src/main/java/com/inspection/camera/util/ImageProcessor.kt
index c5238d4..5ccd873 100644
--- a/app/src/main/java/com/inspection/camera/util/ImageProcessor.kt
+++ b/app/src/main/java/com/inspection/camera/util/ImageProcessor.kt
@@ -99,41 +99,51 @@ object ImageProcessor {
         locationText: String,
         style: WatermarkStyle
     ): Bitmap {
+        android.util.Log.d("ImageProcessor", "addWatermark called, timeText=$timeText, locationText=$locationText")
+        
         val result = sourceBitmap.copy(Bitmap.Config.ARGB_8888, true)
         val canvas = Canvas(result)
+        
+        // 使用固定的字体大小，基于图片宽度比例
+        val baseFontSize = result.width / 40f  // 字体大小为图片宽度的1/40
         val paint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
-            textSize = style.fontSize * result.density
+            textSize = baseFontSize
             color = style.textColor.toArgb()
             typeface = Typeface.DEFAULT_BOLD
+            textAlign = Paint.Align.CENTER
         }
 
         val watermarkText = "$timeText $locationText"
         val textWidth = paint.measureText(watermarkText)
         val textHeight = paint.fontMetrics.let { it.descent - it.ascent }
+        
+        android.util.Log.d("ImageProcessor", "Watermark: width=$textWidth, height=$textHeight, text=$watermarkText")
 
-        // 计算位置（左下角）
-        val padding = 20f * result.density
-        val x = padding
+        // 计算位置（底部中央）
+        val padding = result.width / 30f  // 边距为图片宽度的1/30
+        val x = result.width / 2f
         val y = result.height - padding
 
         // 绘制背景
-        // 通过ARGB判断来决定是否绘制背景，避免混用 Android Color 与 Compose Color 的类型问题
         val bgColorInt = style.backgroundColor.toArgb()
+        android.util.Log.d("ImageProcessor", "Background color int: $bgColorInt")
         if (bgColorInt != 0) {
             val bgPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
                 color = bgColorInt
             }
             val bgRect = RectF(
-                x - 10,
-                y - textHeight - 10,
-                x + textWidth + 10,
-                y + 10
+                x - textWidth / 2 - padding / 2,
+                y - textHeight - padding / 2,
+                x + textWidth / 2 + padding / 2,
+                y + padding / 2
             )
             canvas.drawRoundRect(bgRect, 8f, 8f, bgPaint)
+            android.util.Log.d("ImageProcessor", "Background drawn at x=$x, y=$y")
         }
 
         // 绘制文字
         canvas.drawText(watermarkText, x, y, paint)
+        android.util.Log.d("ImageProcessor", "Text drawn at x=$x, y=$y")
 
         return result
     }