import numpy as np
import matplotlib
matplotlib.use('Agg')  # 使用 Agg 后端
import matplotlib.pyplot as plt
import tempfile as tf
from io import BytesIO

def rd_mem(shape):
  fnames=['lat','lon','data']
  d = []
  for f in fnames:
    filename = f+'.dat'
    d.append(np.memmap(filename, dtype='float32', mode='r', shape=shape))
  return d

def cntr(swLL,neLL):
  with open('params.txt','r') as f:
    line=[i.strip('\n') for i in f][0]
  x0,y0,nx,ny,dx,dy=(float(i) for i in line.split())
  nx,ny=int(nx),int(ny)
  shape=(ny, nx)
  lat,lon,data=rd_mem(shape)
  data = np.where(data < 0, 0, data)
  idx=np.where((lat>=swLL[0])&(lat<=neLL[0])&(lon>=swLL[1])&(lon<=neLL[1]))
  if len(idx[0])==0:
    return 'LL not right!',list(swLL)+list(neLL)
  x=[x0+dx*i for i in range(nx)]
  y=[y0+dy*i for i in range(ny)]
  xg, yg = np.meshgrid(x, y)
  bounds=[np.min(xg[idx[0],idx[1]]),np.max(xg[idx[0],idx[1]]),np.min(yg[idx[0],idx[1]]),np.max(yg[idx[0],idx[1]])]
  ib=[x.index(bounds[0]),x.index(bounds[1]),y.index(bounds[2]),y.index(bounds[3])]
  cmin=data[ib[2]:ib[3]+1,ib[0]:ib[1]+1].min()
  cmax=data[ib[2]:ib[3]+1,ib[0]:ib[1]+1].max()
  levels = np.linspace(cmin, cmax, 10)
  fig, ax = plt.subplots()
  ax.contour(x[ib[0]:ib[1]+1],y[ib[2]:ib[3]+1],data[ib[2]:ib[3]+1,ib[0]:ib[1]+1],levels=levels)
  ran=tf.NamedTemporaryFile().name.replace('/','').replace('tmp','')
  fname='terr_'+ran+'.png'
  output = BytesIO()
  fig.savefig(output, format='png')
  output.seek(0)  # 重置指针位置
  fig.savefig('./pngs/'+fname, format='png')
  return fname,output