Hi there,

How is the rightmost column in `mri_convert -c` calculated?

I have the following fslhd (relevant fields shown only) in a NIFTI image:

```
dim1            208
dim2            300
dim3            320
qto_xyz:1       0.799690    0.022176   0.001352    -86.687996
qto_xyz:2       -0.021442   0.783122   -0.162051  -62.728546
qto_xyz:3       -0.005816   0.161952   0.783414    -174.620270
qto_xyz:4       0.000000    0.000000   0.000000    1.000000
```



After `mri_convert -c`, mri_convert reports the following (relevant fields shown only) in the MGZ image:

```
voxel to ras transform:
               -1.0000  -0.0000   0.0000   128.0225
               -0.0000   0.0000   1.0000  -101.4184
                0.0000  -1.0000  -0.0000   102.4140
                0.0000   0.0000   0.0000     1.0000
```

Shouldn't the right-most column be:
128.5
-128.5
128.5
1
The numbers are (256+1)/2=128.5

Best,
Tashrif