Change default resolution from 70 to 300 dpi

The default resolution is used for images without an explicit resolution
or with an unreasonable resolution (smaller than 70 or larger than 2400).
Signed-off-by: NStefan Weil <sw@weilnetz.de>

api/baseapi.cpp

@@ -106,6 +106,8 @@ const int kMaxIntSize = 22;
 const int kMinCredibleResolution = 70;
 /** Maximum believable resolution.  */
 const int kMaxCredibleResolution = 2400;
+/** Default resolution.  */
+const int kDefaultResolution = 300;
 
 TessBaseAPI::TessBaseAPI()
     : tesseract_(nullptr),
@@ -2199,8 +2201,8 @@ bool TessBaseAPI::Threshold(Pix** pix) {
     // Use the minimum default resolution, as it is safer to under-estimate
     // than over-estimate resolution.
     tprintf("Warning. Invalid resolution %d dpi. Using %d instead.\n", y_res,
-            kMinCredibleResolution);
-    thresholder_->SetSourceYResolution(kMinCredibleResolution);
+            kDefaultResolution);
+    thresholder_->SetSourceYResolution(kDefaultResolution);
   }
   PageSegMode pageseg_mode =
       static_cast<PageSegMode>(