Add dpi attribute to PdfPreview

@@ -7,6 +7,7 @@
 - Fix raster quality on Android
 - Use a CDN for emoji and cupertino fonts
 - Improved Android rendering
+- Add dpi attribute to PdfPreview
 
 ## 5.7.1
 

@@ -40,6 +40,7 @@ class PdfPreviewCustom extends StatefulWidget {
     this.padding,
     this.shouldRepaint = false,
     this.loadingWidget,
+    this.dpi,
   }) : super(key: key);
 
   /// Pdf paper page format
@@ -78,6 +79,10 @@ class PdfPreviewCustom extends StatefulWidget {
   /// If null, a [CircularProgressIndicator] is used instead.
   final Widget? loadingWidget;
 
+  /// The rendering dots per inch resolution
+  /// If not provided, this value is calculated.
+  final double? dpi;
+
   @override
   PdfPreviewCustomState createState() => PdfPreviewCustomState();
 }
@@ -103,6 +108,9 @@ class PdfPreviewCustomState extends State<PdfPreviewCustom>
   static const _errorMessage = 'Unable to display the document';
 
   @override
+  double? get forcedDpi => widget.dpi;
+
+  @override
   void dispose() {
     previewUpdate?.cancel();
     super.dispose();

@@ -60,6 +60,7 @@ class PdfPreview extends StatefulWidget {
     this.shouldRepaint = false,
     this.loadingWidget,
     this.onPageFormatChanged,
+    this.dpi,
   }) : super(key: key);
 
   static const _defaultPageFormats = <String, PdfPageFormat>{
@@ -158,6 +159,10 @@ class PdfPreview extends StatefulWidget {
   /// The page format has changed
   final ValueChanged<PdfPageFormat>? onPageFormatChanged;
 
+  /// The rendering dots per inch resolution
+  /// If not provided, this value is calculated.
+  final double? dpi;
+
   @override
   _PdfPreviewState createState() => _PdfPreviewState();
 }
@@ -323,6 +328,7 @@ class _PdfPreviewState extends State<PdfPreview> {
               previewPageMargin: widget.previewPageMargin,
               scrollViewDecoration: widget.scrollViewDecoration,
               shouldRepaint: widget.shouldRepaint,
+              dpi: widget.dpi,
             ),
           ),
           if (actions.isNotEmpty && widget.useActions)

@@ -48,6 +48,8 @@ mixin PdfPreviewRaster on State<PdfPreviewCustom> {
   /// Dots per inch
   double dpi = PdfPageFormat.inch;
 
+  double? get forcedDpi;
+
   var _rastering = false;
 
   Timer? _previewUpdate;
@@ -62,21 +64,26 @@ mixin PdfPreviewRaster on State<PdfPreviewCustom> {
   void raster() {
     _previewUpdate?.cancel();
     _previewUpdate = Timer(_updateTime, () {
-      final mq = MediaQuery.of(context);
-      final double dpr;
-      if (!kIsWeb && Platform.isAndroid) {
-        if (mq.size.shortestSide * mq.devicePixelRatio < 800) {
-          dpr = 2 * mq.devicePixelRatio;
+      if (forcedDpi != null) {
+        dpi = forcedDpi!;
+      } else {
+        final mq = MediaQuery.of(context);
+        final double dpr;
+        if (!kIsWeb && Platform.isAndroid) {
+          if (mq.size.shortestSide * mq.devicePixelRatio < 800) {
+            dpr = 2 * mq.devicePixelRatio;
+          } else {
+            dpr = mq.devicePixelRatio;
+          }
         } else {
           dpr = mq.devicePixelRatio;
         }
-      } else {
-        dpr = mq.devicePixelRatio;
+        dpi =
+            (min(mq.size.width - 16, widget.maxPageWidth ?? double.infinity)) *
+                dpr /
+                pageFormat.width *
+                PdfPageFormat.inch;
       }
-      dpi = (min(mq.size.width - 16, widget.maxPageWidth ?? double.infinity)) *
-          dpr /
-          pageFormat.width *
-          PdfPageFormat.inch;
 
       _raster();
     });