diff --git a/utils/ImageOutputDev.cc b/utils/ImageOutputDev.cc
index 552a3b15edfdedcfaa5834bdfa8aa23e12534eb7..c438ce33ac57cac9993db65dcdb412426d5815b9 100644
--- a/utils/ImageOutputDev.cc
+++ b/utils/ImageOutputDev.cc
@@ -25,6 +25,7 @@
 // Copyright (C) 2013 Hib Eris <hib@hiberis.nl>
 // Copyright (C) 2017 Caolán McNamara <caolanm@redhat.com>
 // Copyright (C) 2018 Andreas Gruenbacher <agruenba@redhat.com>
+// Copyright (C) 2020 mrbax <12640-mrbax@users.noreply.gitlab.freedesktop.org>
 //
 // To see a description of the changes please see the Changelog file that
 // came with your tarball or type make ChangeLog if you are building from git
@@ -227,10 +228,10 @@ void ImageOutputDev::listImage(GfxState *state, Object *ref, Stream *str, int wi
     }
 
     const double *mat = state->getCTM();
-    double width2 = mat[0] + mat[2];
-    double height2 = mat[1] + mat[3];
-    double xppi = fabs(width * 72.0 / width2) + 0.5;
-    double yppi = fabs(height * 72.0 / height2) + 0.5;
+    double width2 = sqrt(mat[0] * mat[0] + mat[1] * mat[1]);
+    double height2 = sqrt(mat[2] * mat[2] + mat[3] * mat[3]);
+    double xppi = fabs(width * 72.0 / width2);
+    double yppi = fabs(height * 72.0 / height2);
     if (xppi < 1.0)
         printf("%5.3f ", xppi);
     else