Add TrOCR example

rten-examples/Cargo.toml

@@ -64,6 +64,10 @@ path = "src/depth_anything.rs"
 name = "segment_anything"
 path = "src/segment_anything.rs"
 
+[[bin]]
+name = "trocr"
+path = "src/trocr.rs"
+
 # Text
 [[bin]]
 name = "bert_qa"

rten-examples/README.md

@@ -57,6 +57,7 @@ The examples have been chosen to cover common tasks and popular models.
 - **detr** - Object detection using [DETR](https://research.facebook.com/publications/end-to-end-object-detection-with-transformers/)
 - **distilvit** - Image captioning using [Mozilla's DistilViT](https://hacks.mozilla.org/2024/05/experimenting-with-local-alt-text-generation-in-firefox-nightly/)
 - **segment_anything** - Image segmentation using [Segment Anything](https://segment-anything.com)
+- **trocr** - Recognize text using [TrOCR](https://arxiv.org/abs/2109.10282)
 - **yolo** - Object detection using [YOLO v8](https://github.com/ultralytics/ultralytics)
 
 ### Text

rten-examples/src/trocr.rs

@@ -0,0 +1,145 @@
+use std::collections::VecDeque;
+use std::error::Error;
+use std::fs;
+use std::io::prelude::*;
+
+use rten::{FloatOperators, Model};
+use rten_generate::{Generator, GeneratorUtils};
+use rten_imageio::read_image;
+use rten_tensor::prelude::*;
+use rten_tensor::{NdTensor, NdTensorViewMut};
+use rten_text::tokenizers::Tokenizer;
+
+struct Args {
+    encoder_model: String,
+    decoder_model: String,
+    tokenizer_config: String,
+    image_path: String,
+}
+
+fn parse_args() -> Result<Args, lexopt::Error> {
+    use lexopt::prelude::*;
+
+    let mut values = VecDeque::new();
+    let mut parser = lexopt::Parser::from_env();
+
+    while let Some(arg) = parser.next()? {
+        match arg {
+            Value(val) => values.push_back(val.string()?),
+            Long("help") => {
+                println!(
+                    "Generate a caption for an image.
+
+Usage: {bin_name} [options] <encoder_model> <decoder_model> <tokenizer> <image>
+
+Args:
+
+  <encoder_model>  - Image encoder model
+  <decoder_model>  - Text decoder model
+  <tokenizer>      - `tokenizer.json` file
+  <image>          - Image path
+",
+                    bin_name = parser.bin_name().unwrap_or("distilvit")
+                );
+                std::process::exit(0);
+            }
+            _ => return Err(arg.unexpected()),
+        }
+    }
+
+    let encoder_model = values.pop_front().ok_or("missing `encoder_model` arg")?;
+    let decoder_model = values.pop_front().ok_or("missing `decoder_model` arg")?;
+    let tokenizer_config = values.pop_front().ok_or("missing `tokenizer` arg")?;
+    let image_path = values.pop_front().ok_or("missing `image_path` arg")?;
+
+    let args = Args {
+        encoder_model,
+        decoder_model,
+        tokenizer_config,
+        image_path,
+    };
+
+    Ok(args)
+}
+
+fn normalize_pixel(value: f32, channel: usize) -> f32 {
+    assert!(channel < 3, "channel index is invalid");
+
+    // Values taken from `preprocessor_config.json`.
+    let mean = [0.5, 0.5, 0.5];
+    let std_dev = [0.5, 0.5, 0.5];
+
+    (value - mean[channel]) / std_dev[channel]
+}
+
+fn normalize_image(mut img: NdTensorViewMut<f32, 3>) {
+    for chan in 0..img.size(0) {
+        img.slice_mut::<2, _>(chan)
+            .apply(|x| normalize_pixel(*x, chan));
+    }
+}
+
+/// Recognize text line images using TrOCR [^1].
+///
+/// First use Hugging Face's Optimum tool to download and export the models to
+/// ONNX:
+///
+/// ```
+/// optimum-cli export onnx --model microsoft/trocr-base-printed trocr-base-printed
+/// ```
+///
+/// Convert the models to `.rten` format:
+///
+/// ```
+/// rten-convert trocr-base-printed/encoder_model.onnx
+/// rten-convert trocr-base-printed/decoder_model.onnx
+/// ```
+///
+/// Run the model, specifying the image to recognize:
+///
+/// ```sh
+/// cargo run --release --bin trocr trocr-base-printed/encoder_model.rten trocr-base-printed/decoder_model.rten tokenizer.json <image>
+/// ```
+///
+/// [^1]: https://arxiv.org/abs/2109.10282
+fn main() -> Result<(), Box<dyn Error>> {
+    let args = parse_args()?;
+    let encoder_model = unsafe { Model::load_mmap(args.encoder_model)? };
+    let decoder_model = unsafe { Model::load_mmap(args.decoder_model)? };
+    let tokenizer_config = fs::read_to_string(&args.tokenizer_config)?;
+    let tokenizer = Tokenizer::from_json(&tokenizer_config)?;
+    let mut image = read_image(args.image_path)?.into_dyn();
+    image.insert_axis(0); // Add batch dim
+    let mut image = image.resize_image([384, 384])?;
+    normalize_image(image.slice_mut(0));
+
+    let encoded_image: NdTensor<f32, 3> = encoder_model
+        .run_one(image.view().into(), None)?
+        .try_into()?;
+
+    let encoder_hidden_states_id = decoder_model.node_id("encoder_hidden_states")?;
+
+    // `decoder_start_token_id` from `generation_config.json`. This is the `</s>`
+    // token.
+    let decoder_start_token = 2;
+    let eos_token = 2;
+
+    let max_tokens = 100;
+
+    let prompt = vec![decoder_start_token];
+    let generator = Generator::from_model(&decoder_model)?
+        .with_prompt(&prompt)
+        .with_constant_input(encoder_hidden_states_id, encoded_image.view().into())
+        .stop_on_tokens([eos_token])
+        .take(max_tokens)
+        .decode(&tokenizer);
+
+    for token in generator {
+        let token = token?;
+
+        print!("{}", token);
+        let _ = std::io::stdout().flush();
+    }
+
+    Ok(())
+}