ENVI: Mask_Doit

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本文介绍了一种利用IDL编程语言中的mask_doit函数进行遥感影像批量裁剪的方法。通过读取特定目录下的遥感影像文件，使用预定义的多边形区域文件(EVF)确定裁剪范围，并应用到每一幅影像上，最终实现多波段遥感影像的精确裁剪。

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利用mask_doit函数，实现批量裁剪。

compile_opt idl2

  start_path = 'F:\Temporary\data\LC8 Results\'

  cd,start_path

  out_path = 'F:\Temporary\data\LC8 Results\ENVI_clip\temp\ROI\'



  Files = FILE_Search(start_path + 'compo432.tif', count = Filecount)

  ;  FileCount = N_ELEMENTS(Files)

  If FileCount Eq 0 Then Begin

    print, 'File not exist'

    Return

  Endif



  For num = 0, FileCount - 1 do begin

    FileName = Files[num]

    envi_open_file, FileName , r_fid=fid, /no_realize, /invisible

    if (fid eq -1) then begin

      return

    endif

    Print, 'fid=', fid



    ENVI_FILE_QUERY, fid, dims=dims, ns=ns, nl=nl, nb=nb, BNAMES= BNAMES

    t_fid=LONARR(nb)+fid  ;此句的作用？在以后实践中明确。

    pos=LINDGEN(nb)

    

    pos_num = strpos(file_basename(FileName),'.') 

    out_name = out_path + strmid(file_basename(FileName),0, pos_num) + "_roi.tif"

    

    print, out_name

    

    evf_file ='F:\Temporary\data\LC8 Results\Envi_polygon_.evf';

    evf_id=ENVI_EVF_OPEN(evf_file)

    ENVI_EVF_INFO, evf_id, num_recs = num_recs,data_type = data_type,$

      projection = projection, layer_name = layer_name

    roi_ids = LONARR(num_recs)



    For i = 0, num_recs - 1 do begin

      record = ENVI_EVF_READ_RECORD(evf_id, i)

      ENVI_CONVERT_FILE_COORDINATES,fid,xmap,ymap,record[0,*],record[1,*]



      roi_id = ENVI_CREATE_ROI(color = 4, ns = ns , nl = nl)

      ENVI_DEFINE_ROI, roi_id, /polygon, xpts=REFORM(xMap), ypts=REFORM(yMap)

      roi_ids = roi_id



      IF i EQ 0 THEN BEGIN

        xmin = ROUND(MIN(xMap,max = xMax))

        yMin = ROUND(MIN(yMap,max = yMax))

      ENDIF ELSE BEGIN

        xmin = xMin < ROUND(MIN(xMap))

        xMax = xMax > ROUND(MAX(xMap))

        yMin = yMin < ROUND(MIN(yMap))

        yMax = yMax > ROUND(MAX(yMap))

      ENDELSE

    ENDFOR



    xMin = xMin > 0

    xmax = xMax < ns ;- 1 

    yMin = yMin > 0

    ymax = yMax < nl ;- 1



    ENVI_MASK_DOIT,AND_OR = 1, /IN_MEMORY, $

      ROI_IDS= roi_ids, ns = ns, nl = nl, $

      /inside, r_fid = m_fid

    out_dims = [-1,xMin,xMax,yMin,yMax]

    ENVI_MASK_APPLY_DOIT, FID = fid, POS = pos, DIMS = out_dims, $

      M_FID = m_fid, M_POS = m_pos, VALUE = 0, out_name = out_name, R_FID = r_fid, $

      OUT_BNAME = BNAMES, IN_MEMORY = 0

      

      ; 应当理解 M_POS关键字的含义： specify the band position of the mask band.

      ; 因此，令M_POS = m_pos，就能实现对多波段图像的裁剪，而非以前令M_POS = [0]的简单赋值（对单波段图像的处理）。

      ;

    ENVI_FILE_MNG, id =m_fid,/remove

  Endfor



  print,' Clip Done'

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