Depth Anything v2 (#2279)

* define structs

* construct ResidualConvUnit

* forward() for ResidualConvUnit

* implement FeatureFusionBlock

* implement Scratch

* implement DPTHead

* add identity module

* implement forward for DTPHead

* add get_intermediate_layers to DinoVisionTransformer

* implement DepthAnythingV2

* some minor tweaks

* fix compile errors

* fix var builder prefixes

* setup initial example

* use fixed patch size of 37 (518 / 14)

* debugged until output

* print min and max values

* add some dynamism to the output location

* scale input image

* extract prep function

* extract output path function

* normalize image with magic mean and std

* add spectral coloring

* squeeze in the right place

* make enterpolation optional

* use bail instead of panic

* omit unnecessary Shape call

* remove empty curly braces

* use bail instead of assert

* use vb and pp

* remove closures

* extract config object

* Apply rustfmt.

* Fix some clippy lints.

* More lints.

* Use the array methods.

---------

Co-authored-by: laurent <laurent.mazare@gmail.com>

candle-nn/src/ops.rs

@@ -1,4 +1,4 @@
-use candle::{CpuStorage, DType, Layout, Result, Shape, Tensor, D};
+use candle::{CpuStorage, DType, Layout, Module, Result, Shape, Tensor, D};
 use rayon::prelude::*;
 
 /// Applies the softmax function to the input tensor, rescaling the element so that elements on
@@ -926,3 +926,24 @@ pub fn replication_pad2d(xs: &Tensor, pad: usize) -> Result<Tensor> {
         n => candle::bail!("replication-pad with a size of {n} is not supported"),
     }
 }
+
+#[derive(Clone, Debug)]
+pub struct Identity;
+
+impl Identity {
+    pub fn new() -> Identity {
+        Self
+    }
+}
+
+impl Default for Identity {
+    fn default() -> Self {
+        Self
+    }
+}
+
+impl Module for Identity {
+    fn forward(&self, xs: &Tensor) -> Result<Tensor> {
+        Ok(xs.clone())
+    }
+}