Specifying target resolution when resampling with rasterio

Question

In GDAL warp you can simply set an xRes and yRes value. I'm trying to only use rasterio, but the process seems a lot less clear.

According to the docs https://rasterio.readthedocs.io/en/latest/topics/resampling.html you use a upscale or downscale factor to make a new cell resolution. Is there a way to just force a set value? For example, what if your new resolution doesn't divide evenly into your old one?

Answer 1

You just need to figure out the scale factor from your chosen and current pixel size, e.g. I want to resample this 10m resolution "input.tif" to 12.5m:

import rasterio
from rasterio.enums import Resampling

xres, yres = 12.5, 12.5

with rasterio.open("input.tif") as dataset:
    scale_factor_x = dataset.res[0]/xres
    scale_factor_y = dataset.res[1]/yres

    profile = dataset.profile.copy()
    # resample data to target shape
    data = dataset.read(
        out_shape=(
            dataset.count,
            int(dataset.height * scale_factor_y),
            int(dataset.width * scale_factor_x)
        ),
        resampling=Resampling.bilinear
    )

    # scale image transform
    transform = dataset.transform * dataset.transform.scale(
        (1 / scale_factor_x),
        (1 / scale_factor_y)
    )
    profile.update({"height": data.shape[-2],
                    "width": data.shape[-1],
                   "transform": transform})

with rasterio.open("output.tif", "w", **profile) as dataset:
    dataset.write(data)

And here's how the output looks (a single red 10m pixel over the output 12.5m pixels in greyscale):