app.py

import os
import pandas as pd
import numpy as np
import torch
from PIL import Image
from transformers import SegformerForSemanticSegmentation, SegformerFeatureExtractor
from torch import nn
import streamlit as st

img_path = None
st.title('Semantic Segmentation using SegFormer')
file_upload = st.file_uploader('Raw Input Image')
image_path = st.selectbox(
     'Choose any one image for inference',
     ('Select image', 'image1.jpg', 'image2.jpg', 'image3.jpg'))

if file_upload is None:
	raw_image = image_path
else:
	raw_image = file_upload

if raw_image != 'Select image':
	df = pd.read_csv('class_dict_seg.csv')
	classes = df['name']
	palette = df[[' r', ' g', ' b']].values
	id2label = classes.to_dict()
	label2id = {v: k for k, v in id2label.items()}

	image = Image.open(raw_image)
	image = np.asarray(image)
	
	with st.spinner('Loading Model...'):
		feature_extractor = SegformerFeatureExtractor(align=False, reduce_zero_label=False)
		device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
		model = SegformerForSemanticSegmentation.from_pretrained("deep-learning-analytics/segformer_semantic_segmentation", 
																 ignore_mismatched_sizes=True,
		                                                         num_labels=len(id2label), id2label=id2label, label2id=label2id,
		                                                         reshape_last_stage=True)
		model = model.to(device)
		model.eval()
	
	with st.spinner('Preparing image...'):
		# prepare the image for the model (aligned resize)
		feature_extractor_inference = SegformerFeatureExtractor(do_random_crop=False, do_pad=False)
		pixel_values = feature_extractor_inference(image, return_tensors="pt").pixel_values.to(device)

	with st.spinner('Running inference...'):
		outputs = model(pixel_values=pixel_values)# logits are of shape (batch_size, num_labels, height/4, width/4)

	with st.spinner('Postprocessing...'):
		logits = outputs.logits.cpu()
		# First, rescale logits to original image size
		upsampled_logits = nn.functional.interpolate(logits,
		                size=image.shape[:-1], # (height, width)
		                mode='bilinear',
		                align_corners=False)
		# Second, apply argmax on the class dimension
		seg = upsampled_logits.argmax(dim=1)[0]
		color_seg = np.zeros((seg.shape[0], seg.shape[1], 3), dtype=np.uint8) # height, width, 3\
		all_labels = []
		for label, color in enumerate(palette):
		    color_seg[seg == label, :] = color
		    if label in seg:
		    	all_labels.append(id2label[label])
		# Convert to BGR
		color_seg = color_seg[..., ::-1]
	# Show image + mask
	img = np.array(image) * 0.5 + color_seg * 0.5
	img = img.astype(np.uint8)
	st.image(img, caption="Segmented Image")
	st.header("Predicted Labels")
	for idx, label in enumerate(all_labels):
		st.subheader(f'{idx+1}) {label}')