# Copyright (c) OpenMMLab. All rights reserved.
import io
import os.path as osp
from pathlib import Path
import cv2
import numpy as np
from cv2 import (IMREAD_COLOR, IMREAD_GRAYSCALE, IMREAD_IGNORE_ORIENTATION,
IMREAD_UNCHANGED)
from mmcv.utils import check_file_exist, is_str, mkdir_or_exist
try:
from turbojpeg import TJCS_RGB, TJPF_BGR, TJPF_GRAY, TurboJPEG
except ImportError:
TJCS_RGB = TJPF_GRAY = TJPF_BGR = TurboJPEG = None
try:
from PIL import Image, ImageOps
except ImportError:
Image = None
try:
import tifffile
except ImportError:
tifffile = None
jpeg = None
supported_backends = ['cv2', 'turbojpeg', 'pillow', 'tifffile']
imread_flags = {
'color': IMREAD_COLOR,
'grayscale': IMREAD_GRAYSCALE,
'unchanged': IMREAD_UNCHANGED,
'color_ignore_orientation': IMREAD_IGNORE_ORIENTATION | IMREAD_COLOR,
'grayscale_ignore_orientation':
IMREAD_IGNORE_ORIENTATION | IMREAD_GRAYSCALE
}
imread_backend = 'cv2'
[docs]def use_backend(backend):
"""Select a backend for image decoding.
Args:
backend (str): The image decoding backend type. Options are `cv2`,
`pillow`, `turbojpeg` (see https://github.com/lilohuang/PyTurboJPEG)
and `tifffile`. `turbojpeg` is faster but it only supports `.jpeg`
file format.
"""
assert backend in supported_backends
global imread_backend
imread_backend = backend
if imread_backend == 'turbojpeg':
if TurboJPEG is None:
raise ImportError('`PyTurboJPEG` is not installed')
global jpeg
if jpeg is None:
jpeg = TurboJPEG()
elif imread_backend == 'pillow':
if Image is None:
raise ImportError('`Pillow` is not installed')
elif imread_backend == 'tifffile':
if tifffile is None:
raise ImportError('`tifffile` is not installed')
def _jpegflag(flag='color', channel_order='bgr'):
channel_order = channel_order.lower()
if channel_order not in ['rgb', 'bgr']:
raise ValueError('channel order must be either "rgb" or "bgr"')
if flag == 'color':
if channel_order == 'bgr':
return TJPF_BGR
elif channel_order == 'rgb':
return TJCS_RGB
elif flag == 'grayscale':
return TJPF_GRAY
else:
raise ValueError('flag must be "color" or "grayscale"')
def _pillow2array(img, flag='color', channel_order='bgr'):
"""Convert a pillow image to numpy array.
Args:
img (:obj:`PIL.Image.Image`): The image loaded using PIL
flag (str): Flags specifying the color type of a loaded image,
candidates are 'color', 'grayscale' and 'unchanged'.
Default to 'color'.
channel_order (str): The channel order of the output image array,
candidates are 'bgr' and 'rgb'. Default to 'bgr'.
Returns:
np.ndarray: The converted numpy array
"""
channel_order = channel_order.lower()
if channel_order not in ['rgb', 'bgr']:
raise ValueError('channel order must be either "rgb" or "bgr"')
if flag == 'unchanged':
array = np.array(img)
if array.ndim >= 3 and array.shape[2] >= 3: # color image
array[:, :, :3] = array[:, :, (2, 1, 0)] # RGB to BGR
else:
# Handle exif orientation tag
if flag in ['color', 'grayscale']:
img = ImageOps.exif_transpose(img)
# If the image mode is not 'RGB', convert it to 'RGB' first.
if img.mode != 'RGB':
if img.mode != 'LA':
# Most formats except 'LA' can be directly converted to RGB
img = img.convert('RGB')
else:
# When the mode is 'LA', the default conversion will fill in
# the canvas with black, which sometimes shadows black objects
# in the foreground.
#
# Therefore, a random color (124, 117, 104) is used for canvas
img_rgba = img.convert('RGBA')
img = Image.new('RGB', img_rgba.size, (124, 117, 104))
img.paste(img_rgba, mask=img_rgba.split()[3]) # 3 is alpha
if flag in ['color', 'color_ignore_orientation']:
array = np.array(img)
if channel_order != 'rgb':
array = array[:, :, ::-1] # RGB to BGR
elif flag in ['grayscale', 'grayscale_ignore_orientation']:
img = img.convert('L')
array = np.array(img)
else:
raise ValueError(
'flag must be "color", "grayscale", "unchanged", '
f'"color_ignore_orientation" or "grayscale_ignore_orientation"'
f' but got {flag}')
return array
[docs]def imread(img_or_path, flag='color', channel_order='bgr', backend=None):
"""Read an image.
Args:
img_or_path (ndarray or str or Path): Either a numpy array or str or
pathlib.Path. If it is a numpy array (loaded image), then
it will be returned as is.
flag (str): Flags specifying the color type of a loaded image,
candidates are `color`, `grayscale`, `unchanged`,
`color_ignore_orientation` and `grayscale_ignore_orientation`.
By default, `cv2` and `pillow` backend would rotate the image
according to its EXIF info unless called with `unchanged` or
`*_ignore_orientation` flags. `turbojpeg` and `tifffile` backend
always ignore image's EXIF info regardless of the flag.
The `turbojpeg` backend only supports `color` and `grayscale`.
channel_order (str): Order of channel, candidates are `bgr` and `rgb`.
backend (str | None): The image decoding backend type. Options are
`cv2`, `pillow`, `turbojpeg`, `tifffile`, `None`.
If backend is None, the global imread_backend specified by
``mmcv.use_backend()`` will be used. Default: None.
Returns:
ndarray: Loaded image array.
"""
if backend is None:
backend = imread_backend
if backend not in supported_backends:
raise ValueError(f'backend: {backend} is not supported. Supported '
"backends are 'cv2', 'turbojpeg', 'pillow'")
if isinstance(img_or_path, Path):
img_or_path = str(img_or_path)
if isinstance(img_or_path, np.ndarray):
return img_or_path
elif is_str(img_or_path):
check_file_exist(img_or_path,
f'img file does not exist: {img_or_path}')
if backend == 'turbojpeg':
with open(img_or_path, 'rb') as in_file:
img = jpeg.decode(in_file.read(),
_jpegflag(flag, channel_order))
if img.shape[-1] == 1:
img = img[:, :, 0]
return img
elif backend == 'pillow':
img = Image.open(img_or_path)
img = _pillow2array(img, flag, channel_order)
return img
elif backend == 'tifffile':
img = tifffile.imread(img_or_path)
return img
else:
flag = imread_flags[flag] if is_str(flag) else flag
img = cv2.imread(img_or_path, flag)
if flag == IMREAD_COLOR and channel_order == 'rgb':
cv2.cvtColor(img, cv2.COLOR_BGR2RGB, img)
return img
else:
raise TypeError('"img" must be a numpy array or a str or '
'a pathlib.Path object')
[docs]def imfrombytes(content, flag='color', channel_order='bgr', backend=None):
"""Read an image from bytes.
Args:
content (bytes): Image bytes got from files or other streams.
flag (str): Same as :func:`imread`.
backend (str | None): The image decoding backend type. Options are
`cv2`, `pillow`, `turbojpeg`, `None`. If backend is None, the
global imread_backend specified by ``mmcv.use_backend()`` will be
used. Default: None.
Returns:
ndarray: Loaded image array.
"""
if backend is None:
backend = imread_backend
if backend not in supported_backends:
raise ValueError(f'backend: {backend} is not supported. Supported '
"backends are 'cv2', 'turbojpeg', 'pillow'")
if backend == 'turbojpeg':
img = jpeg.decode(content, _jpegflag(flag, channel_order))
if img.shape[-1] == 1:
img = img[:, :, 0]
return img
elif backend == 'pillow':
buff = io.BytesIO(content)
img = Image.open(buff)
img = _pillow2array(img, flag, channel_order)
return img
else:
img_np = np.frombuffer(content, np.uint8)
flag = imread_flags[flag] if is_str(flag) else flag
img = cv2.imdecode(img_np, flag)
if flag == IMREAD_COLOR and channel_order == 'rgb':
cv2.cvtColor(img, cv2.COLOR_BGR2RGB, img)
return img
[docs]def imwrite(img, file_path, params=None, auto_mkdir=True):
"""Write image to file.
Args:
img (ndarray): Image array to be written.
file_path (str): Image file path.
params (None or list): Same as opencv :func:`imwrite` interface.
auto_mkdir (bool): If the parent folder of `file_path` does not exist,
whether to create it automatically.
Returns:
bool: Successful or not.
"""
if auto_mkdir:
dir_name = osp.abspath(osp.dirname(file_path))
mkdir_or_exist(dir_name)
return cv2.imwrite(file_path, img, params)