diff --git a/TimeSeries.pm b/TimeSeries.pm
index aae2e35..c217d80 100644
--- a/TimeSeries.pm
+++ b/TimeSeries.pm
@@ -12,6 +12,7 @@ sub new {
 
     $self->{data} = [];
     $self->{style} = "lines";
+    $self->{output_format} = "png";
 
     return $self;
 }
@@ -39,6 +40,27 @@ sub style {
     return $oldstyle;
 }
 
+sub log_x {
+    my ($self, $log_x) = @_;
+    my $oldlog_x = $self->{log_x};
+    $self->{log_x} = $log_x if ($log_x);
+    return $oldlog_x;
+}
+
+sub log_y {
+    my ($self, $log_y) = @_;
+    my $oldlog_y = $self->{log_y};
+    $self->{log_y} = $log_y if ($log_y);
+    return $oldlog_y;
+}
+
+sub output_format {
+    my ($self, $output_format) = @_;
+    my $oldoutput_format = $self->{output_format};
+    $self->{output_format} = $output_format if ($output_format);
+    return $oldoutput_format;
+}
+
 
 
 sub dstcorr {
@@ -86,6 +108,8 @@ sub plot {
     print $ctlfh "set output '$psfn'\n";
     print $ctlfh "set data style $self->{style}\n";
     print $ctlfh "set grid\n";
+    print $ctlfh "set log x\n" if ($self->{log_x});
+    print $ctlfh "set log y\n" if ($self->{log_y});
 
     # compute ticks
 
@@ -203,19 +227,36 @@ sub plot {
 
 
     my $rc = system("gnuplot", $ctlfn);
-    print STDERR "system returned $rc\n";
+    #print STDERR "system returned $rc\n";
 
-    open(PNG, "gs -sDEVICE=ppmraw -r150 -dBATCH -sOutputFile=- -q - < $psfn |" .
-	   "pnmscale 0.5 |" .
-	   "pnmflip -cw |" .
-	   "pnmcrop |" .
-	   "ppmquant 256 |" .
-	   "ppmtogif |");
+    my $pipe;
 
-    my $png;
-    { local $/ = undef; $png = <PNG>; }
+    if ($self->{output_format} eq "ps") {
+	$pipe = "< $psfn";
+    } else {
+	$pipe = 
+	    "gs -sDEVICE=ppmraw -r150 -dBATCH -sOutputFile=- -q - < $psfn |" .
+	    "pnmscale 0.5 |" .
+	    "pnmflip -cw |" .
+	    "pnmcrop 2> /dev/null |";
+    }
+
+    if ($self->{output_format} eq "png") {
+	$pipe .= "pnmtopng |";
+    }
+    if ($self->{output_format} eq "gif") {
+	$pipe .= "ppmquant 256 2> /dev/null |" .
+	   "ppmtogif |";
+    }
+    if ($self->{output_format} eq "jpeg") {
+	$pipe .= "cjpeg -sample 1x1,1x1,1x1 |";
+    }
+    open(PNG, $pipe);
+
+    my $graph;
+    { local $/ = undef; $graph = <PNG>; }
     close(PNG);
-    return $png;
+    return $graph;
 }
 
 1;
diff --git a/t/0basic.t b/t/0basic.t
new file mode 100644
index 0000000..b907016
--- /dev/null
+++ b/t/0basic.t
@@ -0,0 +1,73 @@
+# Before `make install' is performed this script should be runnable with
+# `make test'. After `make install' it should work as `perl test.pl'
+
+######################### We start with some black magic to print on failure.
+
+# Change 1..1 below to 1..last_test_to_print .
+# (It may become useful if the test is moved to ./t subdirectory.)
+
+BEGIN { $| = 1; print "1..6\n"; }
+END {print "not ok 1\n" unless $loaded;}
+use TimeSeries;
+$loaded = 1;
+print "ok 1\n";
+
+######################### End of black magic.
+
+# Insert your test code below (better if it prints "ok 13"
+# (correspondingly "not ok 13") depending on the success of chunk 13
+# of the test code):
+
+my $test;
+$test = 2;
+my $ts = TimeSeries->new();
+if (defined($ts)) {
+    print "ok $test\n";
+} else {
+    print "not ok $test\n";
+}
+
+$ts->legend("value");
+$ts->add(1.000E9, 5);
+$ts->add(1.001E9, 9);
+$ts->add(1.002E9, 3);
+
+$test = 3;
+my $g = $ts->plot();
+print STDERR "length \$g = ", length($g), "\n";
+if (length($g) > 0 && substr($g, 0, 3) eq "PNG") {
+    print "ok $test\n";
+} else {
+    print "not ok $test\n";
+}
+
+$test = 4;
+$ts->output_format("gif");
+my $g = $ts->plot();
+print STDERR "length \$g = ", length($g), "\n";
+if (length($g) > 0 && substr($g, 0, 6) eq "GIF87a") {
+    print "ok $test\n";
+} else {
+    print "not ok $test\n";
+}
+
+$test = 5;
+$ts->output_format("jpeg");
+my $g = $ts->plot();
+print STDERR "length \$g = ", length($g), "\n";
+if (length($g) > 0 && substr($g, 0, 10) eq "\377\330\377\340\000\020JFIF") {
+    print "ok $test\n";
+} else {
+    print "not ok $test\n";
+}
+
+$test = 6;
+$ts->output_format("ps");
+my $g = $ts->plot();
+print STDERR "length \$g = ", length($g), "\n";
+if (length($g) > 0 && substr($g, 0, 2) eq "%!") {
+    print "ok $test\n";
+} else {
+    print "not ok $test\n";
+}
+