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Source code for torchvision.io.image

from enum import Enum
from typing import List, Union
from warnings import warn

import torch

from ..extension import _load_library
from ..utils import _log_api_usage_once


try:
    _load_library("image")
except (ImportError, OSError) as e:
    warn(
        f"Failed to load image Python extension: '{e}'"
        f"If you don't plan on using image functionality from `torchvision.io`, you can ignore this warning. "
        f"Otherwise, there might be something wrong with your environment. "
        f"Did you have `libjpeg` or `libpng` installed before building `torchvision` from source?"
    )


[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 or ``pathlib.Path``): the path to the file to be read Returns: data (Tensor) """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(read_file) data = torch.ops.image.read_file(str(path)) return data
[docs]def write_file(filename: str, data: torch.Tensor) -> None: """ Writes the contents of an uint8 tensor with one dimension to a file. Args: filename (str or ``pathlib.Path``): the path to the file to be written data (Tensor): the contents to be written to the output file """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(write_file) torch.ops.image.write_file(str(filename), data)
[docs]def decode_png( input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED, apply_exif_orientation: bool = False, ) -> torch.Tensor: """ Decodes a PNG image into a 3 dimensional RGB or grayscale Tensor. Optionally converts the image to the desired format. The values of the output tensor are uint8 in [0, 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. apply_exif_orientation (bool): apply EXIF orientation transformation to the output tensor. Default: False. Returns: output (Tensor[image_channels, image_height, image_width]) """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(decode_png) output = torch.ops.image.decode_png(input, mode.value, False, apply_exif_orientation) 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. """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(encode_png) 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 or ``pathlib.Path``): 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 """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(write_png) output = encode_png(input, compression_level) write_file(filename, output)
[docs]def decode_jpeg( input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED, device: str = "cpu", apply_exif_orientation: bool = False, ) -> torch.Tensor: """ Decodes a JPEG image into a 3 dimensional RGB or grayscale 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. The supported modes are: ``ImageReadMode.UNCHANGED``, ``ImageReadMode.GRAY`` and ``ImageReadMode.RGB`` 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 .. betastatus:: device parameter .. warning:: There is a memory leak in the nvjpeg library for CUDA versions < 11.6. Make sure to rely on CUDA 11.6 or above before using ``device="cuda"``. apply_exif_orientation (bool): apply EXIF orientation transformation to the output tensor. Default: False. Only implemented for JPEG format on CPU. Returns: output (Tensor[image_channels, image_height, image_width]) """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(decode_jpeg) 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, apply_exif_orientation) return output
[docs]def encode_jpeg( input: Union[torch.Tensor, List[torch.Tensor]], quality: int = 75 ) -> Union[torch.Tensor, List[torch.Tensor]]: """ Takes a (list of) input tensor(s) in CHW layout and returns a (list of) buffer(s) with the contents of the corresponding JPEG file(s). .. note:: Passing a list of CUDA tensors is more efficient than repeated individual calls to ``encode_jpeg``. For CPU tensors the performance is equivalent. Args: input (Tensor[channels, image_height, image_width] or List[Tensor[channels, image_height, image_width]]): (list of) uint8 image tensor(s) of ``c`` channels, where ``c`` must be 1 or 3 quality (int): Quality of the resulting JPEG file(s). Must be a number between 1 and 100. Default: 75 Returns: output (Tensor[1] or list[Tensor[1]]): A (list of) one dimensional uint8 tensor(s) that contain the raw bytes of the JPEG file. """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(encode_jpeg) if quality < 1 or quality > 100: raise ValueError("Image quality should be a positive number between 1 and 100") if isinstance(input, list): if not input: raise ValueError("encode_jpeg requires at least one input tensor when a list is passed") if input[0].device.type == "cuda": return torch.ops.image.encode_jpegs_cuda(input, quality) else: return [torch.ops.image.encode_jpeg(image, quality) for image in input] else: # single input tensor if input.device.type == "cuda": return torch.ops.image.encode_jpegs_cuda([input], quality)[0] else: return torch.ops.image.encode_jpeg(input, quality)
[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 or ``pathlib.Path``): Path to save the image. quality (int): Quality of the resulting JPEG file, it must be a number between 1 and 100. Default: 75 """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(write_jpeg) output = encode_jpeg(input, quality) assert isinstance(output, torch.Tensor) # Needed for torchscript write_file(filename, output)
[docs]def decode_image( input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED, apply_exif_orientation: bool = False, ) -> torch.Tensor: """ Detect whether an image is a JPEG, PNG or GIF and performs the appropriate operation to decode the image into a 3 dimensional RGB or grayscale Tensor. Optionally converts the image to the desired format. The values of the output tensor are uint8 in [0, 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. Ignored for GIFs. apply_exif_orientation (bool): apply EXIF orientation transformation to the output tensor. Ignored for GIFs. Default: False. Returns: output (Tensor[image_channels, image_height, image_width]) """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(decode_image) output = torch.ops.image.decode_image(input, mode.value, apply_exif_orientation) return output
[docs]def read_image( path: str, mode: ImageReadMode = ImageReadMode.UNCHANGED, apply_exif_orientation: bool = False, ) -> torch.Tensor: """ Reads a JPEG, PNG or GIF image into a 3 dimensional RGB or grayscale Tensor. Optionally converts the image to the desired format. The values of the output tensor are uint8 in [0, 255]. Args: path (str or ``pathlib.Path``): path of the JPEG, PNG or GIF 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. Ignored for GIFs. apply_exif_orientation (bool): apply EXIF orientation transformation to the output tensor. Ignored for GIFs. Default: False. Returns: output (Tensor[image_channels, image_height, image_width]) """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(read_image) data = read_file(path) return decode_image(data, mode, apply_exif_orientation=apply_exif_orientation)
def _read_png_16(path: str, mode: ImageReadMode = ImageReadMode.UNCHANGED) -> torch.Tensor: data = read_file(path) return torch.ops.image.decode_png(data, mode.value, True)
[docs]def decode_gif(input: torch.Tensor) -> torch.Tensor: """ Decode a GIF image into a 3 or 4 dimensional RGB Tensor. The values of the output tensor are uint8 between 0 and 255. The output tensor has shape ``(C, H, W)`` if there is only one image in the GIF, and ``(N, C, H, W)`` if there are ``N`` images. Args: input (Tensor[1]): a one dimensional contiguous uint8 tensor containing the raw bytes of the GIF image. Returns: output (Tensor[image_channels, image_height, image_width] or Tensor[num_images, image_channels, image_height, image_width]) """ if not torch.jit.is_scripting() and not torch.jit.is_tracing(): _log_api_usage_once(decode_gif) return torch.ops.image.decode_gif(input)

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