onnx: fix pad, unsqueeze (#2317)

* onnx: fix pad, unsqueeze

both implementations have off-by-one errors:
- Pad 'reflect' cycle for eg `dim==3` is `[0,1,2,1]` which has length of
  4 (or `dim*2 - 2`) not 5 (current code `dim*2 - 1`)
- Unsqueeze(-1) for tensor with `dim==3` should be 3 (ie `dim+index+1`)
  not 2 (ie currently `dim+index`)

in addition, Pad is incorrectly calculating the starting padding.
If we want to pad out 2 elements to the start, and we have this cycle
of indices of length 6, then we should skip 4 elements, but currently
we skip 2. A more visual representation of what's going on is below:

```
pad_start: 2
data:      [a,b,c,d]
indices:   [0, 1, 2, 3, 2, 1, 0, 1, 2, 3, 2, 1, 0, ..] // zigzag between 0..4
actual:    skip [ c  d| c  b  a  b]
expected:  ~  skip  ~ [ c  b| a  b  c  d]
```

The values between `[` and `|` are padding and the values between
`|` and `]` in the example should match the original data being padded.

* Fix clippy lints.

---------

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

1 files changed, 1 insertions, 1 deletions

diff --git a/candle-wasm-examples/moondream/src/bin/m.rs b/candle-wasm-examples/moondream/src/bin/m.rs
index 2af6c0d2..27cda1e7 100644
--- a/candle-wasm-examples/moondream/src/bin/m.rs
+++ b/candle-wasm-examples/moondream/src/bin/m.rs
@@ -195,7 +195,7 @@ impl Model {
 }
 impl Model {
     fn load_image(&self, image: Vec<u8>) -> Result<Tensor, JsError> {
-        let img = image::io::Reader::new(std::io::Cursor::new(image))
+        let img = image::ImageReader::new(std::io::Cursor::new(image))
             .with_guessed_format()?
             .decode()
             .map_err(|e| JsError::new(&e.to_string()))?