The flags are:
-xres <float>
Set new X resolution
-yres <float>
Set new Y resolution
-coding <string>
Set coding - eg. NOCODING, LABPACK, etc.
-type <string>
Set type - eg. B_W, XRAY, etc.
-format <string>
Set format - eg. FMTUCHAR, FMTDPCOMPLEX, etc.
-xsize <int>
Set new Xsize
-ysize <int>
Set new Ysize
-bands <int>
Set new Bands
See <vips.h> for a complete list of passible values for type, coding and format.
Be very careful when changing Xsize, Ysize, BandFmt or Bands. edvips does no checking!