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@ -0,0 +1,410 @@
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# OBSS SAHI Tool
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# Code written by Fatih C Akyon, 2020.
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import time
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from typing import Dict, List, Optional, Union, Tuple
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import numpy as np
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import requests
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from PIL import Image
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from numpy import ndarray
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def read_image_as_pil(image: Union[Image.Image, str, np.ndarray]):
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"""
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Loads an image as PIL.Image.Image.
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Args:
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image : Can be image path or url (str), numpy image (np.ndarray) or PIL.Image
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"""
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# https://stackoverflow.com/questions/56174099/how-to-load-images-larger-than-max-image-pixels-with-pil
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Image.MAX_IMAGE_PIXELS = None
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if isinstance(image, Image.Image):
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image_pil = image
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elif isinstance(image, str):
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# read image if str image path is provided
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try:
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image_pil = Image.open(
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requests.get(image, stream=True).raw if str(image).startswith("http") else image
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).convert("RGB")
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except: # handle large/tiff image reading
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try:
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import skimage.io
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except ImportError:
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raise ImportError("Please run 'pip install -U scikit-image imagecodecs' for large image handling.")
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image_sk = skimage.io.imread(image).astype(np.uint8)
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if len(image_sk.shape) == 2: # b&w
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image_pil = Image.fromarray(image_sk, mode="1")
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elif image_sk.shape[2] == 4: # rgba
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image_pil = Image.fromarray(image_sk, mode="RGBA")
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elif image_sk.shape[2] == 3: # rgb
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image_pil = Image.fromarray(image_sk, mode="RGB")
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else:
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raise TypeError(f"image with shape: {image_sk.shape[3]} is not supported.")
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elif isinstance(image, np.ndarray):
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if image.shape[0] < 5: # image in CHW
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image = image[:, :, ::-1]
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image_pil = Image.fromarray(image)
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else:
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raise TypeError("read image with 'pillow' using 'Image.open()'")
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return image_pil
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def get_slice_bboxes(
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image_height: int,
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image_width: int,
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slice_height: int = None,
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slice_width: int = None,
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auto_slice_resolution: bool = True,
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overlap_height_ratio: float = 0.2,
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overlap_width_ratio: float = 0.2,
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) -> List[List[int]]:
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"""Slices `image_pil` in crops.
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Corner values of each slice will be generated using the `slice_height`,
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`slice_width`, `overlap_height_ratio` and `overlap_width_ratio` arguments.
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Args:
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image_height (int): Height of the original image.
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image_width (int): Width of the original image.
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slice_height (int): Height of each slice. Default 512.
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slice_width (int): Width of each slice. Default 512.
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overlap_height_ratio(float): Fractional overlap in height of each
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slice (e.g. an overlap of 0.2 for a slice of size 100 yields an
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overlap of 20 pixels). Default 0.2.
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overlap_width_ratio(float): Fractional overlap in width of each
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slice (e.g. an overlap of 0.2 for a slice of size 100 yields an
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overlap of 20 pixels). Default 0.2.
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auto_slice_resolution (bool): if not set slice parameters such as slice_height and slice_width,
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it enables automatically calculate these params from image resolution and orientation.
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Returns:
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List[List[int]]: List of 4 corner coordinates for each N slices.
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[
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[slice_0_left, slice_0_top, slice_0_right, slice_0_bottom],
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...
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[slice_N_left, slice_N_top, slice_N_right, slice_N_bottom]
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]
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"""
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slice_bboxes = []
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y_max = y_min = 0
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if slice_height and slice_width:
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y_overlap = int(overlap_height_ratio * slice_height)
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x_overlap = int(overlap_width_ratio * slice_width)
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elif auto_slice_resolution:
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x_overlap, y_overlap, slice_width, slice_height = get_auto_slice_params(height=image_height, width=image_width)
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else:
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raise ValueError("Compute type is not auto and slice width and height are not provided.")
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while y_max < image_height:
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x_min = x_max = 0
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y_max = y_min + slice_height
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while x_max < image_width:
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x_max = x_min + slice_width
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if y_max > image_height or x_max > image_width:
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xmax = min(image_width, x_max)
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ymax = min(image_height, y_max)
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xmin = max(0, xmax - slice_width)
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ymin = max(0, ymax - slice_height)
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slice_bboxes.append([xmin, ymin, xmax, ymax])
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else:
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slice_bboxes.append([x_min, y_min, x_max, y_max])
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x_min = x_max - x_overlap
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y_min = y_max - y_overlap
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return slice_bboxes
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class SlicedImage:
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def __init__(self, image, starting_pixel):
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"""
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image: np.array
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Sliced image.
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starting_pixel: list of list of int
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Starting pixel coordinates of the sliced image.
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"""
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self.image = image
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self.starting_pixel = starting_pixel
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class SliceImageResult:
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def __init__(self, original_image_size=None):
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"""
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sliced_image_list: list of SlicedImage
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image_dir: str
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Directory of the sliced image exports.
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original_image_size: list of int
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Size of the unsliced original image in [height, width]
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"""
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self._sliced_image_list: List[SlicedImage] = []
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self.original_image_height = original_image_size[0]
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self.original_image_width = original_image_size[1]
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def add_sliced_image(self, sliced_image: SlicedImage):
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if not isinstance(sliced_image, SlicedImage):
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raise TypeError("sliced_image must be a SlicedImage instance")
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self._sliced_image_list.append(sliced_image)
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@property
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def sliced_image_list(self):
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return self._sliced_image_list
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@property
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def images(self):
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"""Returns sliced images.
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Returns:
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images: a list of np.array
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"""
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images = []
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for sliced_image in self._sliced_image_list:
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images.append(sliced_image.image)
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return images
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@property
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def starting_pixels(self) -> List[int]:
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"""Returns a list of starting pixels for each slice.
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Returns:
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starting_pixels: a list of starting pixel coords [x,y]
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"""
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starting_pixels = []
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for sliced_image in self._sliced_image_list:
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starting_pixels.append(sliced_image.starting_pixel)
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return starting_pixels
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def __len__(self):
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return len(self._sliced_image_list)
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def slice_image(
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image: Union[str, Image.Image],
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slice_height: int = None,
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slice_width: int = None,
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overlap_height_ratio: float = None,
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overlap_width_ratio: float = None,
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auto_slice_resolution: bool = True,
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) -> Tuple[ndarray, ndarray]:
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"""Slice a large image into smaller windows. If output_file_name is given export
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sliced images.
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Args:
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auto_slice_resolution:
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image (str or PIL.Image): File path of image or Pillow Image to be sliced.
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coco_annotation_list (CocoAnnotation): List of CocoAnnotation objects.
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output_file_name (str, optional): Root name of output files (coordinates will
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be appended to this)
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output_dir (str, optional): Output directory
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slice_height (int): Height of each slice. Default 512.
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slice_width (int): Width of each slice. Default 512.
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overlap_height_ratio (float): Fractional overlap in height of each
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slice (e.g. an overlap of 0.2 for a slice of size 100 yields an
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overlap of 20 pixels). Default 0.2.
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overlap_width_ratio (float): Fractional overlap in width of each
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slice (e.g. an overlap of 0.2 for a slice of size 100 yields an
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overlap of 20 pixels). Default 0.2.
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min_area_ratio (float): If the cropped annotation area to original annotation
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ratio is smaller than this value, the annotation is filtered out. Default 0.1.
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out_ext (str, optional): Extension of saved images. Default is the
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original suffix.
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verbose (bool, optional): Switch to print relevant values to screen.
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Default 'False'.
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Returns:
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sliced_image_result: SliceImageResult:
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sliced_image_list: list of SlicedImage
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image_dir: str
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Directory of the sliced image exports.
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original_image_size: list of int
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Size of the unsliced original image in [height, width]
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num_total_invalid_segmentation: int
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Number of invalid segmentation annotations.
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"""
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# read image
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image_pil = read_image_as_pil(image)
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image_width, image_height = image_pil.size
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if not (image_width != 0 and image_height != 0):
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raise RuntimeError(f"invalid image size: {image_pil.size} for 'slice_image'.")
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slice_bboxes = get_slice_bboxes(
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image_height=image_height,
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image_width=image_width,
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auto_slice_resolution=auto_slice_resolution,
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slice_height=slice_height,
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slice_width=slice_width,
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overlap_height_ratio=overlap_height_ratio,
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overlap_width_ratio=overlap_width_ratio,
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)
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t0 = time.time()
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n_ims = 0
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# init images and annotations lists
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sliced_image_result = SliceImageResult(original_image_size=[image_height, image_width])
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image_pil_arr = np.asarray(image_pil)
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# iterate over slices
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for slice_bbox in slice_bboxes:
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n_ims += 1
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# extract image
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tlx = slice_bbox[0]
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tly = slice_bbox[1]
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brx = slice_bbox[2]
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bry = slice_bbox[3]
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image_pil_slice = image_pil_arr[tly:bry, tlx:brx]
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# create sliced image and append to sliced_image_result
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sliced_image = SlicedImage(
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image=image_pil_slice, starting_pixel=[slice_bbox[0], slice_bbox[1]]
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)
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sliced_image_result.add_sliced_image(sliced_image)
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image_numpy = np.array(sliced_image_result.images)
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shift_amount = np.array(sliced_image_result.starting_pixels)
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return image_numpy, shift_amount
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def calc_ratio_and_slice(orientation, slide=1, ratio=0.1):
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"""
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According to image resolution calculation overlap params
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Args:
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orientation: image capture angle
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slide: sliding window
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ratio: buffer value
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Returns:
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overlap params
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"""
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if orientation == "vertical":
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slice_row, slice_col, overlap_height_ratio, overlap_width_ratio = slide, slide * 2, ratio, ratio
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elif orientation == "horizontal":
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slice_row, slice_col, overlap_height_ratio, overlap_width_ratio = slide * 2, slide, ratio, ratio
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elif orientation == "square":
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slice_row, slice_col, overlap_height_ratio, overlap_width_ratio = slide, slide, ratio, ratio
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return slice_row, slice_col, overlap_height_ratio, overlap_width_ratio # noqa
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def calc_resolution_factor(resolution: int) -> int:
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"""
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According to image resolution calculate power(2,n) and return the closest smaller `n`.
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Args:
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resolution: the width and height of the image multiplied. such as 1024x720 = 737280
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Returns:
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"""
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expo = 0
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while np.power(2, expo) < resolution:
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expo += 1
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return expo - 1
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def calc_aspect_ratio_orientation(width: int, height: int) -> str:
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"""
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Args:
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width:
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height:
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Returns:
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image capture orientation
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"""
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if width < height:
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return "vertical"
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elif width > height:
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return "horizontal"
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else:
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return "square"
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def calc_slice_and_overlap_params(resolution: str, height: int, width: int, orientation: str) -> List:
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"""
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This function calculate according to image resolution slice and overlap params.
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Args:
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resolution: str
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height: int
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width: int
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orientation: str
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Returns:
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x_overlap, y_overlap, slice_width, slice_height
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"""
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if resolution == "medium":
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split_row, split_col, overlap_height_ratio, overlap_width_ratio = calc_ratio_and_slice(
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orientation, slide=1, ratio=0.8
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)
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elif resolution == "high":
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split_row, split_col, overlap_height_ratio, overlap_width_ratio = calc_ratio_and_slice(
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orientation, slide=2, ratio=0.4
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)
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elif resolution == "ultra-high":
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split_row, split_col, overlap_height_ratio, overlap_width_ratio = calc_ratio_and_slice(
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orientation, slide=4, ratio=0.4
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)
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else: # low condition
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split_col = 1
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split_row = 1
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overlap_width_ratio = 1
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overlap_height_ratio = 1
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slice_height = height // split_col
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slice_width = width // split_row
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x_overlap = int(slice_width * overlap_width_ratio)
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y_overlap = int(slice_height * overlap_height_ratio)
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return x_overlap, y_overlap, slice_width, slice_height # noqa
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def get_resolution_selector(res: str, height: int, width: int):
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"""
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Args:
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res: resolution of image such as low, medium
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height:
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width:
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Returns:
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trigger slicing params function and return overlap params
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"""
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orientation = calc_aspect_ratio_orientation(width=width, height=height)
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x_overlap, y_overlap, slice_width, slice_height = calc_slice_and_overlap_params(
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|
resolution=res, height=height, width=width, orientation=orientation
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)
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return x_overlap, y_overlap, slice_width, slice_height
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def get_auto_slice_params(height: int, width: int):
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"""
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|
|
According to Image HxW calculate overlap sliding window and buffer params
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|
factor is the power value of 2 closest to the image resolution.
|
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|
factor <= 18: low resolution image such as 300x300, 640x640
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|
18 < factor <= 21: medium resolution image such as 1024x1024, 1336x960
|
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|
21 < factor <= 24: high resolution image such as 2048x2048, 2048x4096, 4096x4096
|
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|
factor > 24: ultra-high resolution image such as 6380x6380, 4096x8192
|
|
|
|
|
Args:
|
|
|
|
|
height:
|
|
|
|
|
width:
|
|
|
|
|
|
|
|
|
|
Returns:
|
|
|
|
|
slicing overlap params x_overlap, y_overlap, slice_width, slice_height
|
|
|
|
|
"""
|
|
|
|
|
resolution = height * width
|
|
|
|
|
factor = calc_resolution_factor(resolution)
|
|
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|
|
if factor <= 18:
|
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|
|
return get_resolution_selector("low", height=height, width=width)
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|
|
elif 18 <= factor < 21:
|
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|
|
return get_resolution_selector("medium", height=height, width=width)
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|
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|
|
elif 21 <= factor < 24:
|
|
|
|
|
return get_resolution_selector("high", height=height, width=width)
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|
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|
|
else:
|
|
|
|
|
return get_resolution_selector("ultra-high", height=height, width=width)
|