Revisiting image resizing

[pvonkaenel]

I've been working with the new ippiResizeSqrPixel API, but recently discovered that the Lanczos interpolation does not provide as good a downsampling as I expected. I then tried the Lanczos in the ippiResizeFilter routine and got much better results.

What's the difference between the ippiResizeSqrPixel and ippiResizeFilter routines andwhy do they produce different results?

Thanks,
Peter

[Vladimir_Dudnik]

Hi Peter,

could you please provide more details on that? It would be nice to have your original image and parameters you use for IPP functions to investigate what might be the problem.

Regards,
Vladimir

[pvonkaenel]

Sure, I'll put something together and upload it. In the meantime, do you expect any difference between ResizeFilter and ResizeSqrPixel when Lanczos is specified? Is the ResizeFilter call doing any additional filtering?

Thanks,
Peter

[Ying_H_Intel]

Hi Peter,

Add one notes from the function experts,

The two functions have slightly different realization of Lanczos method.

In the function ippiResizeSqrPixel it is more academic approach but in the function ippiResizeFilter filtering more depends on the sample values.

So if we do down-sampling with good values (multiplies of image sizes) using ippiResizeFilter, we can get more qualitative picture.

But ippiResizeSqrPixel has more performance and requires less memory under equal status.

Regards,
Ying