need more tuning ?

Modules/chkpixels.f90

@@ -39,7 +39,7 @@ contains
       end do
     end do
 
-    call rgbpix_spit_as_pnm(pixrgb, "rgb.pnm")
+    call rgbpix_spit_as_pnm_8(pixrgb, "rgb.pnm")
 
     deallocate(pixrgb)
 

Modules/pixrgb.f90

@@ -15,7 +15,7 @@ end type
 contains
 !-------------------------------------------------------------------
 !-
-subroutine rgbpix_spit_as_pnm(pic, fname)
+subroutine rgbpix_spit_as_pnm_8(pic, fname)
 
   type(t_pixrgb), intent(in)       ::  pic(:,:)
   character (len=*), intent(in)    ::  fname
@@ -24,14 +24,39 @@ subroutine rgbpix_spit_as_pnm(pic, fname)
 
   open(newunit=io, file=fname)
   write (io, '(a2)') "P3"
-  write (io, '("# spit_rgb_pnm")')
+  write (io, '("# rgbpix_spit_as_pnm_8")')
   write (io, '(i0," ",i0)')  size(pic, 1), size(pic, 2)
   write (io, '(i0)') 255
 
   do iy=1, ubound(pic, 2)
     do ix=1, ubound(pic, 1)
 
-    write(io, "(3I7)") pic(ix, iy)%r, pic(ix, iy)%g, pic(ix, iy)%b
+    write(io, "(3I4)") pic(ix, iy)%r, pic(ix, iy)%g, pic(ix, iy)%b
+
+    enddo
+  enddo
+  close(unit=io)
+
+end subroutine
+!-------------------------------------------------------------------
+!-
+subroutine rgbpix_spit_as_pnm_16(pic, fname)
+
+  type(t_pixrgb), intent(in)       ::  pic(:,:)
+  character (len=*), intent(in)    ::  fname
+
+  integer                               ::  io, ix, iy
+
+  open(newunit=io, file=fname)
+  write (io, '(a2)') "P3"
+  write (io, '("# rgbpix_spit_as_pnm_16")')
+  write (io, '(i0," ",i0)')  size(pic, 1), size(pic, 2)
+  write (io, '(i0)') 65535
+
+  do iy=1, ubound(pic, 2)
+    do ix=1, ubound(pic, 1)
+
+    write(io, "(3I6)") pic(ix, iy)%r, pic(ix, iy)%g, pic(ix, iy)%b
 
     enddo
   enddo

Modules/spitpgm.f90

@@ -87,6 +87,7 @@ subroutine spit_as_pgm_8(pic, fname)
     ! XXX print *, "      max = ", foo
     open(newunit=io, file=fname)
     write (io, '(a2)') "P2"
+    write (io, '(A)')  "# spit_as_pgm_8"
     write (io, '(i0," ",i0)')  size(pic, 1), size(pic, 2)
     write (io, '(i0)') 255