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Source code for torchvision.io.image

import torch

import os
import os.path as osp
import importlib.machinery

from enum import Enum

_HAS_IMAGE_OPT = False

try:
    lib_dir = osp.abspath(osp.join(osp.dirname(__file__), ".."))

    loader_details = (
        importlib.machinery.ExtensionFileLoader,
        importlib.machinery.EXTENSION_SUFFIXES
    )

    extfinder = importlib.machinery.FileFinder(lib_dir, loader_details)  # type: ignore[arg-type]
    ext_specs = extfinder.find_spec("image")

    if os.name == 'nt':
        # Load the image extension using LoadLibraryExW
        import ctypes

        kernel32 = ctypes.WinDLL('kernel32.dll', use_last_error=True)
        with_load_library_flags = hasattr(kernel32, 'AddDllDirectory')
        prev_error_mode = kernel32.SetErrorMode(0x0001)

        kernel32.LoadLibraryW.restype = ctypes.c_void_p
        if with_load_library_flags:
            kernel32.LoadLibraryExW.restype = ctypes.c_void_p

        if ext_specs is not None:
            res = kernel32.LoadLibraryExW(ext_specs.origin, None, 0x00001100)
            if res is None:
                err = ctypes.WinError(ctypes.get_last_error())
                err.strerror += (f' Error loading "{ext_specs.origin}" or any or '
                                 'its dependencies.')
                raise err

        kernel32.SetErrorMode(prev_error_mode)

    if ext_specs is not None:
        torch.ops.load_library(ext_specs.origin)
        _HAS_IMAGE_OPT = True
except (ImportError, OSError):
    pass


[docs]class ImageReadMode(Enum): """ Support for various modes while reading images. Use ``ImageReadMode.UNCHANGED`` for loading the image as-is, ``ImageReadMode.GRAY`` for converting to grayscale, ``ImageReadMode.GRAY_ALPHA`` for grayscale with transparency, ``ImageReadMode.RGB`` for RGB and ``ImageReadMode.RGB_ALPHA`` for RGB with transparency. """ UNCHANGED = 0 GRAY = 1 GRAY_ALPHA = 2 RGB = 3 RGB_ALPHA = 4
[docs]def read_file(path: str) -> torch.Tensor: """ Reads and outputs the bytes contents of a file as a uint8 Tensor with one dimension. Args: path (str): the path to the file to be read Returns: data (Tensor) """ data = torch.ops.image.read_file(path) return data
[docs]def write_file(filename: str, data: torch.Tensor) -> None: """ Writes the contents of a uint8 tensor with one dimension to a file. Args: filename (str): the path to the file to be written data (Tensor): the contents to be written to the output file """ torch.ops.image.write_file(filename, data)
[docs]def decode_png(input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED) -> torch.Tensor: """ Decodes a PNG image into a 3 dimensional RGB Tensor. Optionally converts the image to the desired format. The values of the output tensor are uint8 between 0 and 255. Args: input (Tensor[1]): a one dimensional uint8 tensor containing the raw bytes of the PNG image. mode (ImageReadMode): the read mode used for optionally converting the image. Default: ``ImageReadMode.UNCHANGED``. See `ImageReadMode` class for more information on various available modes. Returns: output (Tensor[image_channels, image_height, image_width]) """ output = torch.ops.image.decode_png(input, mode.value) return output
[docs]def encode_png(input: torch.Tensor, compression_level: int = 6) -> torch.Tensor: """ Takes an input tensor in CHW layout and returns a buffer with the contents of its corresponding PNG file. Args: input (Tensor[channels, image_height, image_width]): int8 image tensor of ``c`` channels, where ``c`` must 3 or 1. compression_level (int): Compression factor for the resulting file, it must be a number between 0 and 9. Default: 6 Returns: Tensor[1]: A one dimensional int8 tensor that contains the raw bytes of the PNG file. """ output = torch.ops.image.encode_png(input, compression_level) return output
[docs]def write_png(input: torch.Tensor, filename: str, compression_level: int = 6): """ Takes an input tensor in CHW layout (or HW in the case of grayscale images) and saves it in a PNG file. Args: input (Tensor[channels, image_height, image_width]): int8 image tensor of ``c`` channels, where ``c`` must be 1 or 3. filename (str): Path to save the image. compression_level (int): Compression factor for the resulting file, it must be a number between 0 and 9. Default: 6 """ output = encode_png(input, compression_level) write_file(filename, output)
[docs]def decode_jpeg(input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED, device: str = 'cpu') -> torch.Tensor: """ Decodes a JPEG image into a 3 dimensional RGB Tensor. Optionally converts the image to the desired format. The values of the output tensor are uint8 between 0 and 255. Args: input (Tensor[1]): a one dimensional uint8 tensor containing the raw bytes of the JPEG image. This tensor must be on CPU, regardless of the ``device`` parameter. mode (ImageReadMode): the read mode used for optionally converting the image. Default: ``ImageReadMode.UNCHANGED``. See ``ImageReadMode`` class for more information on various available modes. device (str or torch.device): The device on which the decoded image will be stored. If a cuda device is specified, the image will be decoded with `nvjpeg <https://developer.nvidia.com/nvjpeg>`_. This is only supported for CUDA version >= 10.1 Returns: output (Tensor[image_channels, image_height, image_width]) """ device = torch.device(device) if device.type == 'cuda': output = torch.ops.image.decode_jpeg_cuda(input, mode.value, device) else: output = torch.ops.image.decode_jpeg(input, mode.value) return output
[docs]def encode_jpeg(input: torch.Tensor, quality: int = 75) -> torch.Tensor: """ Takes an input tensor in CHW layout and returns a buffer with the contents of its corresponding JPEG file. Args: input (Tensor[channels, image_height, image_width])): int8 image tensor of ``c`` channels, where ``c`` must be 1 or 3. quality (int): Quality of the resulting JPEG file, it must be a number between 1 and 100. Default: 75 Returns: output (Tensor[1]): A one dimensional int8 tensor that contains the raw bytes of the JPEG file. """ if quality < 1 or quality > 100: raise ValueError('Image quality should be a positive number ' 'between 1 and 100') output = torch.ops.image.encode_jpeg(input, quality) return output
[docs]def write_jpeg(input: torch.Tensor, filename: str, quality: int = 75): """ Takes an input tensor in CHW layout and saves it in a JPEG file. Args: input (Tensor[channels, image_height, image_width]): int8 image tensor of ``c`` channels, where ``c`` must be 1 or 3. filename (str): Path to save the image. quality (int): Quality of the resulting JPEG file, it must be a number between 1 and 100. Default: 75 """ output = encode_jpeg(input, quality) write_file(filename, output)
[docs]def decode_image(input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED) -> torch.Tensor: """ Detects whether an image is a JPEG or PNG and performs the appropriate operation to decode the image into a 3 dimensional RGB Tensor. Optionally converts the image to the desired format. The values of the output tensor are uint8 between 0 and 255. Args: input (Tensor): a one dimensional uint8 tensor containing the raw bytes of the PNG or JPEG image. mode (ImageReadMode): the read mode used for optionally converting the image. Default: ``ImageReadMode.UNCHANGED``. See ``ImageReadMode`` class for more information on various available modes. Returns: output (Tensor[image_channels, image_height, image_width]) """ output = torch.ops.image.decode_image(input, mode.value) return output
[docs]def read_image(path: str, mode: ImageReadMode = ImageReadMode.UNCHANGED) -> torch.Tensor: """ Reads a JPEG or PNG image into a 3 dimensional RGB Tensor. Optionally converts the image to the desired format. The values of the output tensor are uint8 between 0 and 255. Args: path (str): path of the JPEG or PNG image. mode (ImageReadMode): the read mode used for optionally converting the image. Default: ``ImageReadMode.UNCHANGED``. See ``ImageReadMode`` class for more information on various available modes. Returns: output (Tensor[image_channels, image_height, image_width]) """ data = read_file(path) return decode_image(data, mode)

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