Python matplotlib Drawing and dpi correspondence

DPI indicates the size of the drawing area in the plot is not the outer border of the picture

Dpi=1 600x400

dpi=2 1200x800

Dpi=3 1800x1200

........

Dpi=21 (21x600) x (21x400)---> 12600x8400

Example code:

Import TimeImportscipy.signal as SignallImportNumPy as NPImportmatplotlibImportMatplotlib.pyplot as Plty_axis_last=np.linspace (0.0, 0.0, 21120) plt_x=0plt_arr=np.random.rand (1024, 1)defparse_output (Start_freq, Stop_freq,step, Donser_now_lable,donser, Num_now, min_freq):"""Parse data from Soapy_power"""    #Define SizeX_axis = Np.linspace (Start_freq, Stop_freq, round (Stop_freq-start_freq)))  Y_axis= Np.linspace (0.0, 0.0, round (Stop_freq-start_freq)))  #print (len (x_axis))Donser_now_lable=donser_now_lable+Len (x_axis)#Y_axis Deal    GlobalY_axis_last, plt_x, Plt_arr i=0 Temp_lab=0 forNuminchRange (Donser_now_lable+1,len (donser), 1 ):        ifnum>=Len (donser): Y_axis[i]=0 Temp_lab=len (Donser)-donser_now_lableifNum_now==1: Y_axis[i]=Donser[num]Else: Y_axis[i]= (donser[num]*0.65+y_axis_last[i]*0.35) I=i+1ifi==Len (x_axis): BreakY_axis_last=Y_axis time_stop=time.time ()#FFT Change    iftemp_lab!=0:return-1wave_data1=Y_axis[0:len (X_axis)]#print (len (x_axis))WAVE_DATA2 = Wave_data1 *Signall.hann (len (x_axis)) C=np.fft.fft (Wave_data2[0:len (x_axis)) *2/Len (x_axis)#Print (len (c))D=int (Len (c)/2) Y_axis=ABS (C[0:d]) x_axis.resize (d) Min=100Max=0 forIinchRange (0,len (y_axis), 1 ):        ifY_axis[i]>Max:max=Y_axis[i]ify_axis[i]<Min:min=Y_axis[i]#print (max)        #print (min)                    #X_axis y_axis to buffer & update buffer    ifMin_freq isNone:min_freq=Start_freqifStart_freq = =Min_freq:databuffer= {"timestamp": Time_stop,"x": List (x_axis),"y": List (Y_axis)}Else: databuffer["x"].extend (x_axis) databuffer["y"].extend (Y_axis)ifStop_freq >0:#data_storage.update (DataBuffer)        #Self.plt_arr=np.random.rand (1024x768)        #self.plt_x=0        #print (self.plt_x)        ifplt_x==0:plt_arr=Y_axis plt_arr.resize (Len (y_axis),1)            Print(" First time")        Else: Plt_temp=Y_axis plt_temp.resize (Len (y_axis),1) Plt_arr=np.concatenate (plt_arr,plt_temp), Axis=1)            #print (Self.plt_arr)            ifplt_x%1000==0:Print(plt_x)ifplt_x%1000==0:cm=' Hot'Norm= Matplotlib.colors.Normalize (Vmin=min, vmax=max) Map=plt.imshow (plt_arr,interpolation='Nearest', Cmap=cm,norm=norm, origin='Upper') Plt.xticks ([]) plt.yticks ([]) Plt.axis ('off')                #Plt.colorbar (mappable=map,ax=none,shrink=0.5, pad=0)Plt.savefig ("Filename.png", dpi=1320)                     #plt.show ()                Print("-------------------------->")                Print(plt_x) plt_x+=1Temp_str=Str (num_now)returndonser_now_labledefMain (): Num_now=1donser_now_lable=0 Sys_start_freq= 87000000.0#start Fre 87MHZSys_stop_freq = 108127168.0#Stop Fre 108MHZStep = 10316#5158 # 2579.0 #Bin size 1KHZ new (108127168-87000000)/8192Bins = 2048#4096 #8192 #21120 # 10560 #sampling number MHZ    #time_s = 1 #? timesStop_freq = Sys_start_freq#InitMin_freq =None plt_x=0#donser=np.fromfile ("C:\\users\\administrator\\desktop\\bins\\123.b_le.bin", dtype=np.int16)Donser=np.fromfile ("C:\\users\\administrator\\desktop\\bins\\1.b_le.bin", Dtype=np.int16, count=629145600)#600M 629145600     while1:        #Time_start = Time.time ()Start_freq =Stop_freqifstart_freq>=Sys_stop_freq: BreakStop_freq= start_freq+Bins#print ("Start:", Start_freq)        #print ("Stop:", Stop_freq)donser_now_lable=parse_output (Start_freq,stop_freq, Step,donser_now_lable,donser, Num_now, min_freq) Num_now=num_now+1ifdonser_now_lable>=Len (donser): Breakif __name__=="__main__": Main ()

On the code read into a binary bin data file part 1.08GB, the data format for the packet-free, small-end mode, 16-bit encoded spectral data dpi=1320, generate a picture named Filename.png

Python matplotlib Drawing and dpi correspondence