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"""
Originally inspired by impl at https://github.com/zhunzhong07/Random-Erasing, Apache 2.0
Copyright Zhun Zhong & Liang Zheng
Hacked together by / Copyright 2020 Ross Wightman
Modified by Hangbo Bao, for generating the masked position for visual image transformer
"""
# --------------------------------------------------------
# BEIT: BERT Pre-Training of Image Transformers (https://arxiv.org/abs/2106.08254)
# Github source: https://github.com/microsoft/unilm/tree/master/beit
# Copyright (c) 2021 Microsoft
# Licensed under The MIT License [see LICENSE for details]
# By Hangbo Bao
# Based on timm, DINO and DeiT code bases
# https://github.com/rwightman/pytorch-image-models/tree/master/timm
# Originally inspired by impl at https://github.com/zhunzhong07/Random-Erasing, Apache 2.0
# Copyright Zhun Zhong & Liang Zheng
#
# Hacked together by / Copyright 2020 Ross Wightman
#
# Modified by Hangbo Bao, for generating the masked position for visual image transformer
# --------------------------------------------------------'
import random
import math
import numpy as np
class MaskingGenerator:
def __init__(
self, input_size, num_masking_patches, min_num_patches=4, max_num_patches=None,
min_aspect=0.3, max_aspect=None):
if not isinstance(input_size, tuple):
input_size = (input_size, ) * 2
self.height, self.width = input_size
self.num_patches = self.height * self.width
self.num_masking_patches = num_masking_patches
self.min_num_patches = min_num_patches
self.max_num_patches = num_masking_patches if max_num_patches is None else max_num_patches
max_aspect = max_aspect or 1 / min_aspect
self.log_aspect_ratio = (math.log(min_aspect), math.log(max_aspect))
def __repr__(self):
repr_str = "Generator(%d, %d -> [%d ~ %d], max = %d, %.3f ~ %.3f)" % (
self.height, self.width, self.min_num_patches, self.max_num_patches,
self.num_masking_patches, self.log_aspect_ratio[0], self.log_aspect_ratio[1])
return repr_str
def get_shape(self):
return self.height, self.width
def _mask(self, mask, max_mask_patches):
delta = 0
for attempt in range(10):
target_area = random.uniform(self.min_num_patches, max_mask_patches)
aspect_ratio = math.exp(random.uniform(*self.log_aspect_ratio))
h = int(round(math.sqrt(target_area * aspect_ratio)))
w = int(round(math.sqrt(target_area / aspect_ratio)))
if w < self.width and h < self.height:
top = random.randint(0, self.height - h)
left = random.randint(0, self.width - w)
num_masked = mask[top: top + h, left: left + w].sum()
# Overlap
if 0 < h * w - num_masked <= max_mask_patches:
for i in range(top, top + h):
for j in range(left, left + w):
if mask[i, j] == 0:
mask[i, j] = 1
delta += 1
if delta > 0:
break
return delta
def __call__(self):
mask = np.zeros(shape=self.get_shape(), dtype=np.int32)
mask_count = 0
while mask_count < self.num_masking_patches:
max_mask_patches = self.num_masking_patches - mask_count
max_mask_patches = min(max_mask_patches, self.max_num_patches)
delta = self._mask(mask, max_mask_patches)
if delta == 0:
break
else:
mask_count += delta
# maintain a fix number {self.num_masking_patches}
if mask_count > self.num_masking_patches:
delta = mask_count - self.num_masking_patches
mask_x, mask_y = mask.nonzero()
to_vis = np.random.choice(mask_x.shape[0], delta, replace=False)
mask[mask_x[to_vis], mask_y[to_vis]] = 0
elif mask_count < self.num_masking_patches:
delta = self.num_masking_patches - mask_count
mask_x, mask_y = (mask == 0).nonzero()
to_mask = np.random.choice(mask_x.shape[0], delta, replace=False)
mask[mask_x[to_mask], mask_y[to_mask]] = 1
assert mask.sum() == self.num_masking_patches, f"mask: {mask}, mask count {mask.sum()}"
return mask
if __name__ == '__main__':
import pdb
generator = MaskingGenerator(input_size=14, num_masking_patches=118, min_num_patches=16,)
for i in range(10000000):
mask = generator()
if mask.sum() != 118:
pdb.set_trace()
print(mask)
print(mask.sum()) |