Hi @AntixK ,

If it's in a file, the easiest way is with thumbnail:

x = pyvips.Image.thumbnail("something.jpg", 200, height=300, size="both")

Will size to 200x300 pixels.

If it's an image, use resize and give both an hscale and vscale.

Appreciate the quick response!

I tried the thumbnail method, but it still resizes by the aspect ratio.

Argh, sorry, I should not rely on memory. Try:

$ python3
Python 3.9.7 (default, Sep 10 2021, 14:59:43) 
[GCC 11.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyvips
>>> x = pyvips.Image.thumbnail("k2.jpg", 200, height=300, size="force")
>>> x
<pyvips.Image 200x300 uchar, 3 bands, srgb>

Another related question -

How do I set the interpolation method for resizing the image? According to docs, the default seems to be LANCZOS3.

My goal here is to get a resized image identical to the one I have with PIL. The Lanczos kernel used there seems to be slightly different (Maybe Lanczos2?).

Thank you.

thumbnail picks the best interpolator for you -- it's supposed to do a best practice resize and not give you any options. If you want more control, you need to drop down to a lower level and call reduce directly.

I don't think you can expect identical results. Image resize is complex, with a lot of unspecified parts, and two different implementations are unlikely to handle issues like rounding and centring in an identical way.

How do we use reduce?

Something like this (which is in line with the format in docs) gives error:
pyvips.Image.new_from_array(image).reduce(hshrink=2016/9806, vshrink=1504/6754, kernel="linear", gap=2)
where image is a numpy array.
Error:
Error: reduce needs 3 arguments, but 1 given

Reduce docs: https://libvips.github.io/pyvips/vimage.html#pyvips.Image.reduce

hshrink and vshrink are required arguments, not keyword arguments. Try:

pyvips.Image.new_from_array(image).reduce(2016/9806, 1504/6754, kernel="linear", gap=2)

If your image has an alpha you'll probably want to premultiply. You might need to consider gamma as well.

The main docs are here:

https://www.libvips.org/API/current/libvips-resample.html#vips-reduce