---
title: torch.nn.functional.interpolate
---

## Task: smoothing

def smoothen_pillow(i: Image, f: int = 4):
    w, h = i.width, i.height
    assert w % f == 0
    assert h % f == 0
    i = i.resize((w // f, h // f), resample=BILINEAR)
    i = i.resize((w, h), resample=BILINEAR)
    return i

---

`PIL.Image.Image.resize(..., method=BILINEAR)`

<img src="https://i.imgur.com/VTD8lea.gif" style="width: 50%;" />

---

`F.interpolate(..., align_corners=False, antialias=True)`

<img src="https://i.imgur.com/vte93hr.gif" style="width: 50%;" />

---

`F.interpolate(..., align_corners=False, antialias=True)`

<table><tr>
<td style="width: 25%;">
<img src="https://i.imgur.com/vte93hr.gif" style="width: 100%;" />
</td>
<td>
<ul>
<li>No shifts</li>
<li>Surprisingly close to PIL</li>
</ul>
</td>
</tr></table>

---

PIL vs interpolate(no align, AA)

<img src="https://i.imgur.com/fnDLPr6.gif" style="width: 50%;" />

---

`F.interpolate(..., align_corners=True, antialias=True)`

<img src="https://i.imgur.com/R2IbBVE.gif" style="width: 50%;" />

---

`F.interpolate(..., align_corners=True, antialias=True)`

<table><tr>
<td style="width: 25%;">
<img src="https://i.imgur.com/R2IbBVE.gif" style="width: 100%;" />
</td>
<td>
<ul>
<li>Still no shifts</li>
<li>A "cross" (image of the filter?)</li>
</ul>
</td>

</tr></table>

---

`F.interpolate(..., align_corners=True, antialias=False)`

<img src="https://i.imgur.com/aan2dV8.gif" style="width: 50%;" />

---

`F.interpolate(..., align_corners=True, antialias=False)`

<table><tr>
<td style="width: 25%;">
<img src="https://i.imgur.com/aan2dV8.gif" style="width: 50%;" />
</td>
<td>
<ul>
<li>Still no shifts</li>
<li>Two darkened strips plus darkened blocks</li>
</ul>
</td>

</tr></table>

---

`resize_right.resize`

<img src="https://i.imgur.com/3EE4GW2.gif" style="width: 50%;" />

---

`resize_right.resize`

<table><tr>
<td style="width: 25%;">
<img src="https://i.imgur.com/3EE4GW2.gif" style="width: 50%;" />
</td>
<td>
<ul>
<li>Darkening along the borders</li>
</ul>
</td>

</tr></table>

---

`F.interpolate(..., align_corners=False, antialias=True)`

<img src="https://i.imgur.com/4ppyVTO.gif" style="width: 50%;" />

---

`PIL.Image.Image.resize(..., method=BILINEAR)`

<img src="https://i.imgur.com/hz5DBOw.gif" style="width: 50%;" />

---

interpolate vs PIL

<img src="https://i.imgur.com/bmAC59e.gif" style="width: 50%;" />

---

What does `torch` actually use?

---


---

`HelperInterpLinear::aa_filter`

---


---

...