Gemma3

Overview

The Gemma 3 model was proposed in the Gemma 3 Techncial Report by Google. It is a vision-language model composed by a SigLIP vision encoder and a Gemma 2 language decoder, linked by a multimodal linear projection. It cuts an image into a fixed number of tokens, in the same way as SigLIP, as long as the image does not exceed certain aspect ratio. For images that exceed the given aspect ratio, it crops the image into multiple smaller patches and concatenates them with the base image embedding. One particularity is that the model uses bidirectional attention on all the image tokens. In addition, the model interleaves sliding window local attention with full causal attention in the language backbone, where each sixth layer is a full causal attention layer.

This model was contributed by Ryan Mullins, Raushan Turganbay Arthur Zucker, and Pedro Cuenca.

Usage tips

For image+text and image-only inputs use Gemma3ForConditionalGeneration.
For text-only inputs use Gemma3ForCausalLM for generation to avoid loading the vision tower.
Each sample can contain multiple images, and the number of images can vary between samples. However, make sure to pass correctly batched images to the processor, where each batch is a list of one or more images.
The text passed to the processor should have a <start_of_image> token wherever an image should be inserted.
The processor has its own apply_chat_template method to convert chat messages to model inputs. See the examples below for more details on how to use it.

Image cropping for high resolution images

The model supports cropping images into smaller patches when the image aspect ratio exceeds a certain value. By default the images are not cropped and only the base image is forwarded to the model. Users can set do_pan_and_scan=True to obtain several crops per image along with the base image to improve the quality in DocVQA or similar tasks requiring higher resolution images.

Pan and scan is an inference time optimization to handle images with skewed aspect ratios. When enabled, it improves performance on tasks related to document understanding, infographics, OCR, etc.


processor = AutoProcessor.from_pretrained("google/gemma-3-4b-it", padding_side="left")

url = "https://media.istockphoto.com/id/1192867753/photo/cow-in-berchida-beach-siniscola.jpg?s=612x612&w=0&k=20&c=v0hjjniwsMNfJSuKWZuIn8pssmD5h5bSN1peBd1CmH4="
messages = [
    {
        "role": "system",
        "content": [
            {"type": "text", "text": "You are a helpful assistant."}
        ]
    },
    {
        "role": "user", "content": [
            {"type": "image", "url": url},
            {"type": "text", "text": "What is shown in this image?"},
        ]
    },
]
inputs = processor.apply_chat_template(
    messages,
    tokenize=True,
    return_dict=True,
    return_tensors="pt",
    add_generation_prompt=True,
    do_pan_and_scan=True,
).to(model.device)

Usage Example

Single-image Inference

from transformers import AutoProcessor, Gemma3ForConditionalGeneration

model_id = "google/gemma-3-4b-it"
model = Gemma3ForConditionalGeneration.from_pretrained(model_id, device_map="auto")
processor = AutoProcessor.from_pretrained(model_id, padding_side="left")

url = "https://media.istockphoto.com/id/1192867753/photo/cow-in-berchida-beach-siniscola.jpg?s=612x612&w=0&k=20&c=v0hjjniwsMNfJSuKWZuIn8pssmD5h5bSN1peBd1CmH4="
messages = [
    {
        "role": "system",
        "content": [
            {"type": "text", "text": "You are a helpful assistant."}
        ]
    },
    {
        "role": "user", "content": [
            {"type": "image", "url": url},
            {"type": "text", "text": "What is shown in this image?"},
        ]
    },
]
inputs = processor.apply_chat_template(
    messages,
    tokenize=True,
    return_dict=True,
    return_tensors="pt",
    add_generation_prompt=True,
).to(model.device)

output = model.generate(**inputs, max_new_tokens=50)
print(processor.decode(output[0], skip_special_tokens=True)[inputs.input_ids.shape[1]: ])

Multi-image Inference

model_id = "google/gemma-3-4b-it"
model = Gemma3ForConditionalGeneration.from_pretrained(model_id, device_map="auto")
processor = AutoProcessor.from_pretrained(model_id, padding_side="left")

url_cow = "https://media.istockphoto.com/id/1192867753/photo/cow-in-berchida-beach-siniscola.jpg?s=612x612&w=0&k=20&c=v0hjjniwsMNfJSuKWZuIn8pssmD5h5bSN1peBd1CmH4="
url_stop = "https://www.ilankelman.org/stopsigns/australia.jpg"
messages = [
    {
        "role": "system",
        "content": [
            {"type": "text", "text": "You are a helpful assistant."}
        ]
    },
    {
        "role": "user", "content": [
            {"type": "image", "url": url_cow},
            {"type": "image", "url": url_stop},
            {"type": "text", "text": "Are these two images identical?"},
        ]
    },
]
inputs = processor.apply_chat_template(
    messages,
    tokenize=True,
    return_dict=True,
    return_tensors="pt",
    add_generation_prompt=True,
).to(model.device)

output = model.generate(**inputs, max_new_tokens=50)
print(processor.decode(output[0], skip_special_tokens=True)[inputs.input_ids.shape[1]: ])

Text-only inference

You can use the VLMs for text-only generation by omitting images in your input. However, you can also load the models in text-only mode as shown below. This will skip loading the vision tower and will save resources when you just need the LLM capabilities.

from transformers import AutoTokenizer, Gemma3ForCausalLM

model_id = "google/gemma-3-1b-it"

tokenizer = AutoTokenizer.from_pretrained(model_id)
model = Gemma3ForCausalLM.from_pretrained(model_id, device_map="auto")

input_ids = tokenizer("Write me a poem about Machine Learning.", return_tensors="pt").to(model.device)

outputs = model.generate(**input_ids, max_new_tokens=100)
text = tokenizer.batch_decode(outputs, skip_special_tokens=True)

print(text)

Transformers

Gemma3

Overview

Usage tips

Image cropping for high resolution images

Usage Example

Single-image Inference

Multi-image Inference

Text-only inference

Gemma3ImageProcessor

class transformers.Gemma3ImageProcessor

pan_and_scan

preprocess

Gemma3ImageProcessorFast

class transformers.Gemma3ImageProcessorFast

pan_and_scan

preprocess

Gemma3Processor

class transformers.Gemma3Processor

batch_decode

decode

Gemma3TextConfig

class transformers.Gemma3TextConfig

Gemma3Config

class transformers.Gemma3Config

Gemma3TextModel

class transformers.Gemma3TextModel

forward

Gemma3ForCausalLM

class transformers.Gemma3ForCausalLM

forward

Gemma3ForConditionalGeneration

class transformers.Gemma3ForConditionalGeneration

forward