app.py

import torch
import torch.nn as nn
import torch.nn.functional as F
from torchvision import transforms
from einops import rearrange
import gradio as gr
from PIL import Image
import math

# Configuration
cfg = {
    "image_size": 32,
    "patch_size": 4,
    "in_channels": 3,
    "num_classes": 100,
    "emb_dim": 192,
    "num_heads": 6,
    "depth": 6,
    "mlp_ratio": 4.0,
    "drop": 0.1,
    "drop_path": 0.1
}

# CIFAR-100 class names
classes = [
    'apple', 'aquarium_fish', 'baby', 'bear', 'beaver', 'bed', 'bee', 'beetle', 
    'bicycle', 'bottle', 'bowl', 'boy', 'bridge', 'bus', 'butterfly', 'camel', 
    'can', 'castle', 'caterpillar', 'cattle', 'chair', 'chimpanzee', 'clock', 
    'cloud', 'cockroach', 'couch', 'crab', 'crocodile', 'cup', 'dinosaur', 
    'dolphin', 'elephant', 'flatfish', 'forest', 'fox', 'girl', 'hamster', 
    'house', 'kangaroo', 'keyboard', 'lamp', 'lawn_mower', 'leopard', 'lion', 
    'lizard', 'lobster', 'man', 'maple_tree', 'motorcycle', 'mountain', 'mouse', 
    'mushroom', 'oak_tree', 'orange', 'orchid', 'otter', 'palm_tree', 'pear', 
    'pickup_truck', 'pine_tree', 'plain', 'plate', 'poppy', 'porcupine', 
    'possum', 'rabbit', 'raccoon', 'ray', 'road', 'rocket', 'rose', 'sea', 
    'seal', 'shark', 'shrew', 'skunk', 'skyscraper', 'snail', 'snake', 'spider', 
    'squirrel', 'streetcar', 'sunflower', 'sweet_pepper', 'table', 'tank', 
    'telephone', 'television', 'tiger', 'tractor', 'train', 'trout', 'tulip', 
    'turtle', 'wardrobe', 'whale', 'willow_tree', 'wolf', 'woman', 'worm'
]

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

class ConvPatchEmbed(nn.Module):
    def __init__(self, img_size=32, in_chans=3, embed_dim=192):
        super().__init__()
        # 32x32 -> 32x32 -> 16x16 -> 16x16
        self.proj = nn.Sequential(
            nn.Conv2d(in_chans, 64, kernel_size=3, stride=1, padding=1, bias=False),
            nn.BatchNorm2d(64),
            nn.ReLU(inplace=True),

            nn.Conv2d(64, 128, kernel_size=3, stride=2, padding=1, bias=False),  # 32 -> 16
            nn.BatchNorm2d(128),
            nn.ReLU(inplace=True),

            nn.Conv2d(128, embed_dim, kernel_size=3, stride=1, padding=1, bias=False),  # stays 16x16
            nn.BatchNorm2d(embed_dim),
            nn.ReLU(inplace=True),
        )

        grid_size = (img_size // 2, img_size // 2)  # (16,16)
        self.grid_size = grid_size
        self.num_patches = grid_size[0] * grid_size[1]

    def forward(self, x):
        x = self.proj(x)         # (B, E, H=16, W=16)
        B, C, H, W = x.shape
        x = x.flatten(2).transpose(1, 2)  # (B, N=H*W, E)
        return x

class MLP(nn.Module):
    def __init__(self, in_features, hidden_features=None, drop=0.):
        super().__init__()
        hidden_features = hidden_features or in_features
        self.fc1 = nn.Linear(in_features, hidden_features)
        self.act = nn.GELU()
        self.fc2 = nn.Linear(hidden_features, in_features)
        self.drop = nn.Dropout(drop)

    def forward(self, x):
        x = self.fc1(x)
        x = self.act(x)
        x = self.drop(x)
        x = self.fc2(x)
        x = self.drop(x)
        return x

class Attention(nn.Module):
    def __init__(self, dim, num_heads=8, qkv_bias=True, attn_drop=0., proj_drop=0.):
        super().__init__()
        self.num_heads = num_heads
        head_dim = dim // num_heads
        self.scale = head_dim ** -0.5

        self.qkv = nn.Linear(dim, dim * 3, bias=qkv_bias)
        self.attn_drop = nn.Dropout(attn_drop)
        self.proj = nn.Linear(dim, dim)
        self.proj_drop = nn.Dropout(proj_drop)

    def forward(self, x):
        B, N, C = x.shape
        # (B, N, 3C) -> (3, B, heads, N, head_dim)
        qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads).permute(2, 0, 3, 1, 4)
        q, k, v = qkv[0], qkv[1], qkv[2]

        attn = (q @ k.transpose(-2, -1)) * self.scale
        attn = attn.softmax(dim=-1)
        attn = self.attn_drop(attn)

        x = (attn @ v).transpose(1, 2).reshape(B, N, C)
        x = self.proj(x)
        x = self.proj_drop(x)
        return x

# Simple Stochastic Depth
class StochasticDepth(nn.Module):
    def __init__(self, p):
        super().__init__()
        self.p = float(p)

    def forward(self, x):
        if not self.training or self.p == 0.0:
            return x
        keep_prob = 1.0 - self.p
        shape = (x.shape[0],) + (1,) * (x.ndim - 1)
        random_tensor = keep_prob + torch.rand(shape, dtype=x.dtype, device=x.device)
        random_tensor.floor_()
        return x / keep_prob * random_tensor

class Block(nn.Module):
    def __init__(self, dim, num_heads, mlp_ratio=4., drop=0., attn_drop=0., drop_path=0.):
        super().__init__()
        self.norm1 = nn.LayerNorm(dim)
        self.attn = Attention(dim, num_heads=num_heads, attn_drop=attn_drop, proj_drop=drop)
        self.drop_path = StochasticDepth(drop_path) if drop_path > 0. else nn.Identity()
        self.norm2 = nn.LayerNorm(dim)
        self.mlp = MLP(dim, int(dim * mlp_ratio), drop=drop)

    def forward(self, x):
        x = x + self.drop_path(self.attn(self.norm1(x)))
        x = x + self.drop_path(self.mlp(self.norm2(x)))
        return x

class ViT(nn.Module):
    def __init__(self, cfg):
        super().__init__()
        img_size = cfg["image_size"]

        self.patch_embed = ConvPatchEmbed(
            img_size=img_size,
            in_chans=cfg["in_channels"],
            embed_dim=cfg["emb_dim"]
        )
        n_patches = self.patch_embed.num_patches

        self.cls_token = nn.Parameter(torch.zeros(1, 1, cfg["emb_dim"]))
        self.pos_embed = nn.Parameter(torch.zeros(1, 1 + n_patches, cfg["emb_dim"]))
        self.pos_drop = nn.Dropout(p=cfg["drop"])

        # stochastic depth decay rule
        dpr = torch.linspace(0, cfg["drop_path"], cfg["depth"]).tolist()
        self.blocks = nn.ModuleList([
            Block(
                dim=cfg["emb_dim"],
                num_heads=cfg["num_heads"],
                mlp_ratio=cfg["mlp_ratio"],
                drop=cfg["drop"],
                drop_path=dpr[i]
            )
            for i in range(cfg["depth"])
        ])
        self.norm = nn.LayerNorm(cfg["emb_dim"])
        self.head = nn.Linear(cfg["emb_dim"], cfg["num_classes"])

        # init
        nn.init.trunc_normal_(self.pos_embed, std=.02)
        nn.init.trunc_normal_(self.cls_token, std=.02)
        self.apply(self._init_weights)

    def _init_weights(self, m):
        if isinstance(m, nn.Linear):
            nn.init.xavier_uniform_(m.weight)
            if m.bias is not None:
                nn.init.zeros_(m.bias)
        elif isinstance(m, nn.LayerNorm):
            nn.init.zeros_(m.bias)
            nn.init.ones_(m.weight)
        elif isinstance(m, nn.Conv2d):
            nn.init.kaiming_normal_(m.weight, mode="fan_out", nonlinearity="relu")
            if getattr(m, "bias", None) is not None:
                nn.init.zeros_(m.bias)

    def forward(self, x):
        B = x.shape[0]
        x = self.patch_embed(x)                   # (B, N, E)
        cls_tokens = self.cls_token.expand(B, -1, -1)
        x = torch.cat((cls_tokens, x), dim=1)     # (B, 1+N, E)
        x = x + self.pos_embed
        x = self.pos_drop(x)

        for blk in self.blocks:
            x = blk(x)

        x = self.norm(x)
        cls = x[:, 0]
        out = self.head(cls)
        return out


# Load model weights
checkpoint = torch.load("Revised_best_ViT_CIFAR100_baseline_checkpoint.pth", map_location=device)

model = ViT(cfg).to(device)

# Load only the model weights
model.load_state_dict(checkpoint["model_state"])
model.eval()


# Image preprocessing
transform = transforms.Compose([
    transforms.Resize((32,32)),
    transforms.ToTensor(),
    transforms.Normalize((0.5071, 0.4867, 0.4408), (0.2675, 0.2565, 0.2761))  # CIFAR-100 stats
])

def predict(img: Image.Image):
    img_t = transform(img).unsqueeze(0).to(device)
    with torch.no_grad():
        out = model(img_t)
        probs = torch.softmax(out, dim=1)[0]
        top5 = probs.topk(5)
    result = {classes[i]: float(probs[i]) for i in top5.indices}
    return result

# Gradio interface
iface = gr.Interface(
    fn=predict,
    inputs=gr.Image(type="pil"),
    outputs=gr.Label(num_top_classes=5, label="Top-5 Predictions"),
    title="Hybrid ViT+CNN CIFAR-100 Classifier",
    description="Upload a 32x32 image, and the model predicts the CIFAR-100 class.",
    examples=["_20230926_on_kangaroos.jpg",
             "complex-aerial-view-city.jpg",
             "apples-101-about-1440x810.webp",
             "detect(1).jpg",
             "Arabian-dromedary-camel-calf.webp",
             "1_9527341a-93b9-4566-9eb3-3bfe92cfed5f.webp"]
)

iface.launch()