Source code for ts.torch_handler.image_classifier

"""
Module for image classification default handler
"""
import torch
import torch.nn.functional as F
from torchvision import transforms

from ts.handler_utils.timer import timed

from ..utils.util import map_class_to_label
from .vision_handler import VisionHandler


class ImageClassifier(VisionHandler):
    """
    ImageClassifier handler class. This handler takes an image
    and returns the name of object in that image.
    """

    topk = 5
    # These are the standard Imagenet dimensions
    # and statistics
    image_processing = transforms.Compose(
        [
            transforms.Resize(256),
            transforms.CenterCrop(224),
            transforms.ToTensor(),
            transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]),
        ]
    )

    def set_max_result_classes(self, topk):
        self.topk = topk

    def get_max_result_classes(self):
        return self.topk

    @timed
    def postprocess(self, data):
        ps = F.softmax(data, dim=1)
        probs, classes = torch.topk(ps, self.topk, dim=1)
        probs = probs.tolist()
        classes = classes.tolist()
        return map_class_to_label(probs, self.mapping, classes)