One of the problems of arbitrary dimensioned images is that it becomes
necessary for software to handle the general case. It is easier to write
application software if it is known in advance that all images will
have a specific size (e.g. 
) and a specific orientation
(e.g. the first pixel is at the patient's anterior, right side).
By setting the icv property MI_ICV_DO_DIM_CONV to TRUE
these conversions can be done automatically. The orientation of
spatial axes is determined by the properties MI_ICV_XDIM_DIR,
MI_ICV_YDIM_DIR and MI_ICV_ZDIM_DIR. These affect any
image dimensions that are MI?space or MI?frequency where
? corresponds to x, y or z. These
properties can have values MI_ICV_POSITIVE,
MI_ICV_NEGATIVE or MI_ICV_ANYDIR. The last of these will
prevent flipping of the dimension. The first two will flip the
dimension if necessary so that the attribute MIstep of the
dimension variable will have the correct sign.
The two image dimensions are referred to as dimensions A and B.
Dimension A is the fastest varying dimension of the two. Setting
properties MI_ICV_ADIM_SIZE and MI_ICV_BDIM_SIZE specify
the desired size for the image dimension. Dimensions are resized so
that the file image will fit entirely in the calling program's image,
and is centred in the image. The size MI_ICV_ANYSIZE allows
one of the dimensions to have a variable size. If property
MI_ICV_KEEP_ASPECT is set to TRUE, then the two
dimensions are rescaled by the same amount. It is possible to inquire
about the new step and start, corresponding to attributes
MIstep and MIstart (where pixel position = ipixel*step +
start, with ipixel counting from zero). The properties
MI_ICV_?DIM_STEP and MI_ICV_?DIM_START (? =
A or B) are set automatically and can be inquired but
not set.
Although vector images are allowed, many applications would rather
only deal with scalar images (one intensity value at each point).
Setting MI_ICV_DO_SCALAR to TRUE (the default) will
cause vector images to be converted to scalar images by averaging the
components. (Thus, RGB images are automatically converted to
gray-scale images in this simple way).
It can sometimes be useful for a program to perform dimension
conversions on three (or perhaps more) dimensions, not just the two
standard image dimensions. To perform dimension flipping and/or
resizing on dimensions beyond the usual two, the property
MI_ICV_NUM_IMGDIMS can be set to an integer value between
one and MI_MAX_IMGDIMS. To set the size of a dimension,
set the property MI_ICV_DIM_SIZE (analogous to
MI_ICV_ADIM_SIZE). To specify the dimension to be set, add
the dimension to the property (adding zero corresponds to the fastest
varying dimension -- add zero for the ``A'' dimension, one for the
``B'' dimension, etc.). Voxel separation and
location can be inquired about through the properties
MI_ICV_DIM_STEP and MI_ICV_DIM_START (analogous to
MI_ICV_ADIM_STEP and MI_ICV_ADIM_START), again
adding the dimension number to the property.