Resizing is blurry

Windows 10

ImageMagick 7.0.10-12 Q16x64 2020-05-15

Wand 0.6.1

I do:

i.resize(width=new_width, height=new_heigh, filter='triangle', blur=-1)

Result: blurry with the comparable image size. Say, original width is 640, new width is 610. Filter and blur params don't seem to infulence anything. I tried blur=0, blur=0.1. As for filter, i tried filter=undefined.

How can I cope with this blurry problem?

Your issue is that blur values are >0. You have specified a negative value. If you want sharpening, use values between 0 and 1.

The documentation at http://docs.wand-py.org/en/0.5.9/wand/image.html says:

blur (numbers.Real) – the blur factor where > 1 is blurry, < 1 is sharp. default is 1

So in Python/Wand it would be for example:

Input:

from wand.image import Image
from wand.display import display

with Image(filename='pigeons.jpg') as img:
    img.resize(width=550, height=350, filter='triangle', blur=0.5)
    img.save(filename='pigeons_resized.png')
    display(img)

Result:

Note that you might get better results using filter=lanczos