There is an undocumented way to do this. With undocumented code, we cannot guarantee it will function the same way in the future but it seems like these routines have not changed in a while. Here is an example: pro subset_by_evf compile_opt idl2 ;select input file to subset fname = 'C:\Program Files\ITT\IDL70\products\envi45\data\world_dem' envi_open_file, fname, r_fid=fid if (fid[0] eq -1) then return envi_file_query, fid, bnames=bnames, sname=sname ;open vector file to use for subset and get id evf_fname = 'C:\Program Files\ITT\IDL70\products\envi45\data\vector\states_.evf' ;make sure envi vector routine is available envi_check_save, /vector ;open the vector and get its ID evf_open, evf_fname, vec=vec, /no_warning evf_id = vec.id ;compute the spatial boundary based on the evf using ROI routines (undocumented routine) - this will provide the DIMS to use to subset roi_ids = envi_get_roi_ids(fid=fid, /include_evfs) envi_roi_compute_spatial_boundry, roi_ids, dims, fid=fid ;resize the original image by the new dimensions envi_doit, 'resize_doit', fid=fid, dims=dims, pos=pos, $ rfact=[1.,1.], /in_memory, r_fid=sub_fid envi_file_query, sub_fid, ns=ns, nl=nl, dims=dims ;generate a mask from the evf (undocumented routine) - you need to mask areas outside of EVF boundaries if the EVF is not a rectangle ; this is the same as using Basic Tools ->Subset data via ROIs and masking the outside of the ROI/EVF boundary envi_mask_doit, evf_id=evf_id, evf_fid=sub_fid, ns=ns, nl=nl, and_or=0, $ /inside, /in_memory, r_fid=m_fid ;apply the mask to the subset image out_name=sname+'_subset' envi_mask_apply_doit, fid=sub_fid, pos=pos, dims=dims, m_fid=m_fid, m_pos=0l, $ value=-9999, out_bname=bnames, out_name=out_name ;close in memory files envi_file_mng, id=m_fid, /remove envi_file_mng, id=sub_fid, /remove envi_evf_close, evf_id end

This is terrific; I can do exactly what I need to do, now. Thank you, MariM very much!

Hi Mari, How can I put an option to 'mask' or 'not to mask' in the outside of ROI (like subset in ENVI). Please note: I am using the lines given below to extract the data within ROI and masking the data outside ROIwith -9999. Please suggest me what modification is required in these lines sothat even outside the ROI it should not mask the data with -9999 but keep theactual data like inside ROI in order to make ROI data as rectangular instead ofas shape file polygon. I would appreciate your kind cooperation. envi_mask_doit, evf_id=evf_id, evf_fid=sub_fid, ns=ns, nl=nl, and_or=0, $ /inside,/in_memory, r_fid=m_fid ;apply the maskto the subset image envi_mask_apply_doit, fid=sub_fid, pos=pos, dims=dims, m_fid=m_fid,m_pos=0l, $ value=-9999,out_bname=bnames,out_name=file_out

To opt to 'mask' or 'not to mask' in the outside of ROI, you can use the keyword INSIDE with envi_mask_doit. Setting the INSIDE=0 in your code will apply the inverse mask. -Xiaoying Exelis VIS