set term png {small | medium | large} {monochrome | gray | color}
后面两项分别代表图中字体的大小和图像的颜色（黑白，灰度，彩色，默认彩色可以用xRRGGBB的RGB值来表示颜色）
其实，可以另存为矢量图像，这样看起来会更清晰，gnuplot支持emf格式的矢量图像：
set term emf
set output "1-2.emf"
此时代表文字大小的 {small | medium | large} 不可用，默认仍然是彩色图像，另外，set size 不可用（可用执行，但是效果不会改变图像大小，只会改变有效图像在整个图像中的面积，如 set size 0.5,0.5，那么，仅左下四分之一处有图像，其余空白）
BTW：可以使用set grid 20 来设置显示网格，其中20代表使用的线型，与plot中使用的线型使用一样的数值表示（个人感觉20号线型做网格还不错:)）
附：gnuplot支持的图像类型列表：
aed512 AED 512 Terminal
aed767 AED 767 Terminal
aifm Adobe Illustrator 3.0 Format
bitgraph BBN Bitgraph Terminal
cgm Computer Graphics Metafile
corel EPS format for CorelDRAW
dumb printer or glass dumb terminal
dxf dxf-file for AutoCad (default size 120x80)
eepic EEPIC -- extended LaTeX picture environment
emf Enhanced Metafile format
emtex LaTeX picture environment with emTeX specials
epslatex LaTeX (Text) and encapsulated PostScript
epson_180dpi Epson LQ-style 180-dot per inch (24 pin) printers
epson_60dpi Epson-style 60-dot per inch printers
epson_lx800 Epson LX-800, Star NL-10, NX-1000, PROPRINTER ...
fig FIG graphics language for XFIG graphics editor
gif GIF format [mode] [fontsize] [size] [colors]
gpic GPIC -- Produce graphs in groff using the gpic preprocessor
hp2623A HP2623A and maybe others
hp2648 HP2648 and HP2647
hp500c HP DeskJet 500c, [75 100 150 300] [rle tiff]
hpdj HP DeskJet 500, [75 100 150 300]
hpgl HP7475 and relatives [number of pens] [eject]
hpljii HP Laserjet series II, [75 100 150 300]
hppj HP PaintJet and HP3630 [FNT5X9 FNT9X17 FNT13X25]
imagen Imagen laser printer
jpeg JPEG images using libgd and TrueType fonts
kc_tek40xx MS-DOS Kermit Tek4010 terminal emulator - color
km_tek40xx MS-DOS Kermit Tek4010 terminal emulator - monochrome
latex LaTeX picture environment
mf Metafont plotting standard
mif Frame maker MIF 3.00 format
mp MetaPost plotting standard
nec_cp6 NEC printer CP6, Epson LQ-800 [monocrome color draft]
okidata OKIDATA 320/321 Standard
pbm Portable bitmap [small medium large] [monochrome gray color]
pcl5 HP Designjet 750C, HP Laserjet III/IV, etc. (many options)
pdf PDF (Portable Document File) file driver
png PNG images using libgd and TrueType fonts
postscript PostScript graphics language [mode "fontname" font_size]
pslatex LaTeX picture environment with PostScript /specials
pstex plain TeX with PostScript /specials
pstricks LaTeX picture environment with PSTricks macros
qms QMS/QUIC Laser printer (also Talaris 1200 and others)
regis REGIS graphics language
rgip RGIP metafile (Uniplex). Option: fontsize (1-8)
selanar Selanar
starc Star Color Printer
svg W3C Scalable Vector Graphics driver
table Dump ASCII table of X Y [Z] values to output
tandy_60dpi Tandy DMP-130 series 60-dot per inch graphics
tek40xx Tektronix 4010 and others; most TEK emulators
tek410x Tektronix 4106, 4107, 4109 and 420X terminals
texdraw LaTeX texdraw environment
tgif TGIF X11 [mode] [x,y] [dashed] ["font" [fontsize]]
tkcanvas Tk/Tcl canvas widget [perltk] [interactive]
tpic TPIC -- LaTeX picture environment with tpic /specials
uniplex RGIP metafile (Uniplex). Option: fontsize (1-8) (Same as rgip)
unknown Unknown terminal type - not a plotting device
vttek VT-like tek40xx terminal emulator
x11 X11 Window System
X11 X11 Window System (identical to x11)
xlib X11 Window System (gnulib_x11 dump)
![Learning Perl: 1.3. How Can I Get Perl?[图]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)