Gnuplot给我倾斜的图像

Question

我一直试图在gnuplot上绘制一些数据，但是它给我的图像是倾斜的。

这是我正在使用的代码：

reset

set terminal postscript eps enhanced dashed color defaultplex "Helvetica" 25

set nokey
#set title "(f)"
set xrange[0:1]
set yrange[0:50]


#set xlabel'{/Symbol e}' #eixo x
#set ylabel'{/Symbol d}' #eixo y


set cbrange[0:9]
set palette defined (0 "white",\
1.8 "white",1.8 "black",2.2 "black",2.2 "white",\
2.8 "white",2.8 "white",3.2 "white",3.2 "white",\
3.8 "white",3.8 "pink",4.2 "pink",4.2 "white",\
5.8 "white",5.8 "blue",6.2 "blue",6.2 "white",\
7.8 "white",7.8 "red",8.2 "red",8.2 "white",\
9.0 "white")
set output 'periodosz.eps'
plot 'periodos.dat' using 1:2:3 with image, \
     'return_1_menos.dat' using 1:2 with lines lt 1 lc rgb "#7F00FF" ,\
     'return_1_mais.dat' using 1:2 with lines lt 1 lc rgb "#003300" , \
     'return_2_mais.dat' using 1:2 with lines lt 1 lc rgb "green" , \
     'return_2_menos.dat' using 1:2 with lines lt 1 lc rgb "#FF8000" ,\
     'return_3_mais.dat' using 1:2 with lines lt 1 lc rgb "yellow" , \
     'return_3_menos.dat' using 1:2 with lines lt 1 lc rgb "#660000"

该如何解决？