functional.py

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# encoding: utf-8
"""
@author:  liaoxingyu
@contact: sherlockliao01@gmail.com
"""
 
import numpy as np
import torch
from PIL import Image, ImageOps, ImageEnhance
 
 
def to_tensor(pic):
    """Convert a ``PIL Image`` or ``numpy.ndarray`` to tensor.
 
    See ``ToTensor`` for more details.
 
    Args:
        pic (PIL Image or numpy.ndarray): Image to be converted to tensor.
 
    Returns:
        Tensor: Converted image.
    """
    if isinstance(pic, np.ndarray):
        assert len(pic.shape) in (2, 3)
        # handle numpy array
        if pic.ndim == 2:
            pic = pic[:, :, None]
 
        img = torch.from_numpy(pic.transpose((2, 0, 1)))
        # backward compatibility
        if isinstance(img, torch.ByteTensor):
            return img.float()
        else:
            return img
 
    # handle PIL Image
    if pic.mode == 'I':
        img = torch.from_numpy(np.array(pic, np.int32, copy=False))
    elif pic.mode == 'I;16':
        img = torch.from_numpy(np.array(pic, np.int16, copy=False))
    elif pic.mode == 'F':
        img = torch.from_numpy(np.array(pic, np.float32, copy=False))
    elif pic.mode == '1':
        img = 255 * torch.from_numpy(np.array(pic, np.uint8, copy=False))
    else:
        img = torch.ByteTensor(torch.ByteStorage.from_buffer(pic.tobytes()))
    # PIL image mode: L, LA, P, I, F, RGB, YCbCr, RGBA, CMYK
    if pic.mode == 'YCbCr':
        nchannel = 3
    elif pic.mode == 'I;16':
        nchannel = 1
    else:
        nchannel = len(pic.mode)
    img = img.view(pic.size[1], pic.size[0], nchannel)
    # put it from HWC to CHW format
    # yikes, this transpose takes 80% of the loading time/CPU
    img = img.transpose(0, 1).transpose(0, 2).contiguous()
    if isinstance(img, torch.ByteTensor):
        return img.float()
    else:
        return img
 
 
def int_parameter(level, maxval):
    """Helper function to scale `val` between 0 and maxval .
    Args:
      level: Level of the operation that will be between [0, `PARAMETER_MAX`].
      maxval: Maximum value that the operation can have. This will be scaled to
        level/PARAMETER_MAX.
    Returns:
      An int that results from scaling `maxval` according to `level`.
    """
    return int(level * maxval / 10)
 
 
def float_parameter(level, maxval):
    """Helper function to scale `val` between 0 and maxval.
    Args:
      level: Level of the operation that will be between [0, `PARAMETER_MAX`].
      maxval: Maximum value that the operation can have. This will be scaled to
        level/PARAMETER_MAX.
    Returns:
      A float that results from scaling `maxval` according to `level`.
    """
    return float(level) * maxval / 10.
 
 
def sample_level(n):
    return np.random.uniform(low=0.1, high=n)
 
 
def autocontrast(pil_img, *args):
    return ImageOps.autocontrast(pil_img)
 
 
def equalize(pil_img, *args):
    return ImageOps.equalize(pil_img)
 
 
def posterize(pil_img, level, *args):
    level = int_parameter(sample_level(level), 4)
    return ImageOps.posterize(pil_img, 4 - level)
 
 
def rotate(pil_img, level, *args):
    degrees = int_parameter(sample_level(level), 30)
    if np.random.uniform() > 0.5:
        degrees = -degrees
    return pil_img.rotate(degrees, resample=Image.BILINEAR)
 
 
def solarize(pil_img, level, *args):
    level = int_parameter(sample_level(level), 256)
    return ImageOps.solarize(pil_img, 256 - level)
 
 
def shear_x(pil_img, level, image_size):
    level = float_parameter(sample_level(level), 0.3)
    if np.random.uniform() > 0.5:
        level = -level
    return pil_img.transform(image_size,
                             Image.AFFINE, (1, level, 0, 0, 1, 0),
                             resample=Image.BILINEAR)
 
 
def shear_y(pil_img, level, image_size):
    level = float_parameter(sample_level(level), 0.3)
    if np.random.uniform() > 0.5:
        level = -level
    return pil_img.transform(image_size,
                             Image.AFFINE, (1, 0, 0, level, 1, 0),
                             resample=Image.BILINEAR)
 
 
def translate_x(pil_img, level, image_size):
    level = int_parameter(sample_level(level), image_size[0] / 3)
    if np.random.random() > 0.5:
        level = -level
    return pil_img.transform(image_size,
                             Image.AFFINE, (1, 0, level, 0, 1, 0),
                             resample=Image.BILINEAR)
 
 
def translate_y(pil_img, level, image_size):
    level = int_parameter(sample_level(level), image_size[1] / 3)
    if np.random.random() > 0.5:
        level = -level
    return pil_img.transform(image_size,
                             Image.AFFINE, (1, 0, 0, 0, 1, level),
                             resample=Image.BILINEAR)
 
 
# operation that overlaps with ImageNet-C's test set
def color(pil_img, level, *args):
    level = float_parameter(sample_level(level), 1.8) + 0.1
    return ImageEnhance.Color(pil_img).enhance(level)
 
 
# operation that overlaps with ImageNet-C's test set
def contrast(pil_img, level, *args):
    level = float_parameter(sample_level(level), 1.8) + 0.1
    return ImageEnhance.Contrast(pil_img).enhance(level)
 
 
# operation that overlaps with ImageNet-C's test set
def brightness(pil_img, level, *args):
    level = float_parameter(sample_level(level), 1.8) + 0.1
    return ImageEnhance.Brightness(pil_img).enhance(level)
 
 
# operation that overlaps with ImageNet-C's test set
def sharpness(pil_img, level, *args):
    level = float_parameter(sample_level(level), 1.8) + 0.1
    return ImageEnhance.Sharpness(pil_img).enhance(level)
 
 
augmentations_reid = [
    autocontrast, equalize, posterize, shear_x, shear_y,
    color, contrast, brightness, sharpness
]
 
augmentations = [
    autocontrast, equalize, posterize, rotate, solarize, shear_x, shear_y,
    translate_x, translate_y
]
 
augmentations_all = [
    autocontrast, equalize, posterize, rotate, solarize, shear_x, shear_y,
    translate_x, translate_y, color, contrast, brightness, sharpness
]