> ## Documentation Index
> Fetch the complete documentation index at: https://docs.strandai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Set slide pixel size

> Set user-reported microns per pixel when a slide's physical scale metadata is missing or incorrect.

Microns per pixel (MPP) describes the physical size represented by one
base-level image pixel. Strand uses this scale when normalizing slide pixels
for inference. An incorrect value can change the biological scale of the
image regions sent to the model.

Set an override after uploading the slide and before submitting a prediction
when the embedded scale is missing or known to be wrong. The user-reported
value takes precedence over embedded slide metadata for subsequent jobs.

## Isotropic pixels

Use one value when the horizontal and vertical scales are the same:

<CodeGroup>
  ```bash REST theme={"dark"}
  curl -X PATCH "https://app.strandai.com/api/v1/samples/$SAMPLE_ID" \
    -H "Authorization: Bearer $STRAND_API_KEY" \
    -H "Content-Type: application/json" \
    -d '{"mpp": 0.26}'
  ```

  ```python Python theme={"dark"}
  client.samples.patch(upload.id, mpp=0.26)
  ```

  ```r R theme={"dark"}
  strand_patch_sample(client, upload$id, mpp = 0.26)
  ```
</CodeGroup>

The value must be greater than 0 and at most 100 microns per pixel. The
response echoes the persisted `mpp` value.

Strand slides are isotropic, so a single scale governs both axes. The REST
endpoint also accepts an `{ "x", "y" }` object when both axes are equal; an
object with differing axes is rejected.