Rotation of a 2D image without changing the size

kraji

When we use rotation matrix transformation
to rotate a 2D image about a point, the size
of the image changes except for a rotation of
90,180, 270 and 360 degrees. Although
inbuilt function is written in matlab and
photoshop, the size of the image changes
after rotation in boththe softwares.
This is because, the pixel
positions are integer values, and when the
transformation is applied to each and every
piel value of the image, more than one
pixel is transformed to the same position (
because of rounding off)in the rotated image
and hence some of the pixel intensities are
overwitten .
How to overcome this problem?