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import numpy as np | |
from PIL import Image | |
import torch.nn.functional as F | |
from typing import List | |
from transformers import CLIPProcessor, CLIPModel | |
NUM_ASPECT=5 | |
ROUND_DIGIT=3 | |
MAX_LENGTH = 76 | |
MAX_NUM_FRAMES=8 | |
CLIP_POINT_LOW=0.27 | |
CLIP_POINT_MID=0.31 | |
CLIP_POINT_HIGH=0.35 | |
class MetricCLIPScore(): | |
def __init__(self, device="cuda") -> None: | |
""" | |
Initialize a MetricCLIPScore object with the specified device. | |
Args: | |
device (str, optional): The device on which the model will run. Defaults to "cuda". | |
""" | |
self.device = device | |
self.model = CLIPModel.from_pretrained("openai/clip-vit-base-patch32") | |
self.model.to(self.device) | |
self.tokenizer = CLIPProcessor.from_pretrained("openai/clip-vit-base-patch32") | |
def evaluate(self, frame_list:List[Image.Image], text:str,): | |
""" | |
Calculate the cosine similarity of between CLIP features of text prompt and each frame of a given video to test text-to-video alignment, | |
then quantize the orginal output based on some predefined thresholds. | |
Args: | |
frame_list:List[Image.Image], frames of the video used in calculation. | |
text:str, text prompt for generating the video. | |
Returns: | |
clip_score_avg: float, the computed average CLIP-Score between each frame and the text prompt. | |
quantized_ans: int, the quantized value of the above avg SSIM scores based on pre-defined thresholds. | |
""" | |
device=self.model.device | |
input_t = self.tokenizer(text=text, max_length=MAX_LENGTH, truncation=True, return_tensors="pt", padding=True).to(device) | |
cos_sim_list=[] | |
for image in frame_list: | |
input_f = self.tokenizer(images=image, return_tensors="pt", padding=True).to(device) | |
output_t = self.model.get_text_features(**input_t).flatten() | |
output_f = self.model.get_image_features(**input_f).flatten() | |
cos_sim = F.cosine_similarity(output_t, output_f, dim=0).item() | |
cos_sim_list.append(cos_sim) | |
clip_score_avg=np.mean(cos_sim_list) | |
quantized_ans=0 | |
if clip_score_avg < CLIP_POINT_LOW: | |
quantized_ans=1 | |
elif clip_score_avg >= CLIP_POINT_LOW and clip_score_avg < CLIP_POINT_MID: | |
quantized_ans=2 | |
elif clip_score_avg >= CLIP_POINT_MID and clip_score_avg < CLIP_POINT_HIGH: | |
quantized_ans=3 | |
else: | |
quantized_ans=4 | |
return clip_score_avg, quantized_ans | |