[Openexr-devel] modify datawindow in input EXR file header

[ZiZi Zhao]

After I open an EXR image and detect its true datawindow, can I directly
modify the xmin, ymin, xmax, ymax values in the input EXR header? Do I
have to open and write a new EXR file with datawindow Cropped Image?

Is the input EXR image file opened in ImfOpenInputFile( filename ) with
"r+" or "r" only ?

If not, it seems that I have to open a new EXR image file and set new
datawindow values in header, but everything else stays the same as the
input EXR image. 

Thanks in advance,

zizi