[Bugfix] Fix Nemotron VL image processing (#22739)

Co-authored-by: ducviet00-h2 <[email protected]>

Author: ducviet00

tests/models/multimodal/processing/test_nemotron_vl.py

@@ -23,15 +23,15 @@ def _get_expected_num_patches(
     min_num: int,
     max_num: int,
 ):
-    from vllm.model_executor.models.internvl import (
-        calculate_internvl_targets, get_internvl_target_ratios)
+    from vllm.model_executor.models.nemotron_vl import (
+        calculate_nemotron_vl_targets, get_nemotron_vl_target_ratios)
 
     width, height = image.size
 
-    blocks, _, _ = calculate_internvl_targets(
+    blocks, _, _ = calculate_nemotron_vl_targets(
         orig_width=width,
         orig_height=height,
-        target_ratios=get_internvl_target_ratios(
+        target_ratios=get_nemotron_vl_target_ratios(
             min_num,
             max_num,
         ),

vllm/model_executor/models/nemotron_vl.py

@@ -13,6 +13,7 @@
 
 import torch
 import torch.nn as nn
+import torchvision.transforms as T
 from PIL import Image
 from transformers import AutoModel, PretrainedConfig
 from transformers.image_processing_utils_fast import BaseImageProcessorFast
@@ -27,6 +28,7 @@
 from vllm.model_executor.models.module_mapping import MultiModelKeys
 from vllm.model_executor.sampling_metadata import SamplingMetadata
 from vllm.multimodal import MULTIMODAL_REGISTRY
+from vllm.multimodal.image import convert_image_mode
 from vllm.multimodal.inputs import NestedTensors
 from vllm.multimodal.processing import PromptUpdateDetails
 from vllm.sequence import IntermediateTensors
@@ -44,6 +46,146 @@
 IMG_CONTEXT = '<image>'
 
 
+def build_transform(input_size: int):
+    return T.Compose([
+        T.Lambda(lambda img: convert_image_mode(img, 'RGB')),
+        T.Resize((input_size, input_size),
+                 interpolation=T.InterpolationMode.BICUBIC),
+        T.ToTensor(),
+    ])
+
+
+# adapted from https://huggingface.co/nvidia/Llama-3.1-Nemotron-Nano-VL-8B-V1
+def find_closest_aspect_ratio(
+    aspect_ratio: float,
+    target_ratios: list[tuple[int, int]],
+    *,
+    width: int,
+    height: int,
+    image_size: int,
+) -> tuple[int, int]:
+    best_factor = float('-inf')
+    best_ratio = (1, 1)
+    area = width * height
+
+    for rw, rh in target_ratios:
+        target_aspect_ratio = rw / rh
+        size_factor = min((rw * rh * image_size * image_size) / area, 0.6)
+        ratio_closeness = min(target_aspect_ratio / aspect_ratio,
+                              aspect_ratio / target_aspect_ratio)
+        factor = size_factor * ratio_closeness
+
+        if factor > best_factor:
+            best_factor = factor
+            best_ratio = (rw, rh)
+
+    return best_ratio
+
+
+def calculate_nemotron_vl_targets(
+    *,
+    orig_width: int,
+    orig_height: int,
+    target_ratios: list[tuple[int, int]],
+    image_size: int,
+    use_thumbnail: bool,
+) -> tuple[int, int, int]:
+    aspect_ratio = orig_width / orig_height
+
+    # find the closest aspect ratio to the target
+    target_aspect_ratio = find_closest_aspect_ratio(
+        aspect_ratio,
+        target_ratios,
+        width=orig_width,
+        height=orig_height,
+        image_size=image_size,
+    )
+
+    # calculate the target width and height
+    target_width = image_size * target_aspect_ratio[0]
+    target_height = image_size * target_aspect_ratio[1]
+    blocks = target_aspect_ratio[0] * target_aspect_ratio[1]
+
+    # add thumbnail image if num_blocks != 1
+    if use_thumbnail and blocks != 1:
+        blocks += 1
+
+    return blocks, target_width, target_height
+
+
+def dynamic_preprocess_nemotron_vl(
+    image: Image.Image,
+    *,
+    target_ratios: list[tuple[int, int]],
+    image_size: int,
+    use_thumbnail: bool,
+) -> list[Image.Image]:
+    orig_width, orig_height = image.size
+
+    # calculate the number of blocks without thumbnail
+    blocks, target_width, target_height = calculate_nemotron_vl_targets(
+        orig_width=orig_width,
+        orig_height=orig_height,
+        target_ratios=target_ratios,
+        image_size=image_size,
+        use_thumbnail=False,
+    )
+
+    # resize the image
+    resized_img = image.resize((target_width, target_height))
+    processed_images = []
+    for i in range(blocks):
+        box = ((i % (target_width // image_size)) * image_size,
+               (i // (target_width // image_size)) * image_size,
+               ((i % (target_width // image_size)) + 1) * image_size,
+               ((i // (target_width // image_size)) + 1) * image_size)
+        # split the image
+        split_img = resized_img.crop(box)
+        processed_images.append(split_img)
+
+    assert len(processed_images) == blocks
+
+    if use_thumbnail and len(processed_images) != 1:
+        thumbnail_img = image.resize((image_size, image_size))
+        processed_images.append(thumbnail_img)
+
+    return processed_images
+
+
+def get_nemotron_vl_target_ratios(
+    min_num: int,
+    max_num: int,
+) -> list[tuple[int, int]]:
+    target_ratios = {(i, j)
+                     for n in range(min_num, max_num + 1)
+                     for i in range(1, n + 1)
+                     for j in range(1, n + 1) if min_num <= i * j <= max_num}
+    return sorted(target_ratios, key=lambda x: x[0] * x[1])
+
+
+def image_to_pixel_values_nemotron_vl(
+    image: Image.Image,
+    *,
+    input_size: int,
+    min_num: int,
+    max_num: int,
+    use_thumbnail: bool,
+) -> torch.Tensor:
+    target_ratios = get_nemotron_vl_target_ratios(min_num, max_num)
+
+    transform = build_transform(input_size=input_size)
+
+    images = dynamic_preprocess_nemotron_vl(
+        image,
+        target_ratios=target_ratios,
+        image_size=input_size,
+        use_thumbnail=use_thumbnail,
+    )
+
+    pixel_values = torch.stack([transform(image) for image in images])
+    return pixel_values
+
+
 class NemotronVLProcessor(InternVLProcessor):
 
     def __init__(
@@ -87,6 +229,50 @@ def __init__(
     def image_token_id(self) -> int:
         return self.tokenizer.get_vocab()[IMG_CONTEXT]
 
+    def get_num_image_tokens(
+        self,
+        *,
+        image_width: int,
+        image_height: int,
+    ) -> int:
+        target_ratios = self.resolve_target_ratios(
+            use_thumbnail=False,  # Applied in calculate_targets
+        )
+
+        num_patches, _, _ = calculate_nemotron_vl_targets(
+            orig_width=image_width,
+            orig_height=image_height,
+            image_size=self.image_size,
+            target_ratios=target_ratios,
+            use_thumbnail=self.use_thumbnail,
+        )
+
+        return num_patches * self.num_image_token
+
+    def _images_to_pixel_values_lst(
+        self,
+        images: list[Image.Image],
+        min_dynamic_patch: Optional[int] = None,
+        max_dynamic_patch: Optional[int] = None,
+        dynamic_image_size: Optional[bool] = None,
+    ) -> list[torch.Tensor]:
+        min_num, max_num = self.resolve_min_max_num(
+            min_dynamic_patch=min_dynamic_patch,
+            max_dynamic_patch=max_dynamic_patch,
+            dynamic_image_size=dynamic_image_size,
+            use_thumbnail=False,  # Applied in image_to_pixel_values
+        )
+
+        return [
+            image_to_pixel_values_nemotron_vl(
+                image,
+                input_size=self.image_size,
+                min_num=min_num,
+                max_num=max_num,
+                use_thumbnail=self.use_thumbnail,
+            ) for image in images
+        ]
+
     def _preprocess_image(
         self,
         text: list[str],