It would be nice to see a test case. Could you provide it?
I think that performance impact is a combination of the following:

3 planes of
4008x2672 each;
 some impact from performance of '
sin' and '
cos' functions used internallyby
IPP, when angles are not
90,
180 or
270 degrees.You know how a new pixel's position is calculated: wx = x*cosA  y*sinA and
wy = x*sinA + y*cosA. So, you have 4 multiplicationsand2 adds/subs. In total, there are more than
192 million of FP operations to rotate an image for5 degrees, for example;
 a performance of aninterpolation algorithm.
I see more and more caseslike yours since sizes of imageshavedramatically increased.
Nikonrecently announced a
36MP DSLR camera.
Nokia announced a
41MP smartphone. I don't know if
IntelSoftware Engineers evertested
IPP with images like I mentioned above. I'm personally interested in
processing of
32Kx32K images and larger.
By the way, I saw a singnificantly worse performance from
Microsoft's ImagingAPI. It is simply impossible
to use!
Best regards,
Sergey