python - 使用 python 从二值图像中裁剪感兴趣区域

Question

要求是从二值图像中裁剪出感兴趣的区域。

我需要通过移除感兴趣区域周围的额外空间来从二值图像中提取一个矩形图像。

例如:从这个Original图片我只想要 region of interest用黄色矩形标记。

注意:黄色矩形仅供引用，不会出现在将要处理的图像中。

我尝试了以下 python 代码，但它没有提供所需的输出。

from PIL import Image
from skimage.io import imread
from skimage.morphology import convex_hull_image
import numpy as np
from matplotlib import pyplot as plt
from skimage import io
from skimage.color import rgb2gray
im = imread('binaryImageEdited.png')
plt.imshow(im)
plt.title('input image')
plt.show()
# create a binary image
im1 = 1 - rgb2gray(im)
threshold = 0.8
im1[im1 <= threshold] = 0
im1[im1 > threshold] = 1
chull = convex_hull_image(im1)
plt.imshow(chull)
plt.title('convex hull in the binary image')
plt.show()
imageBox = Image.fromarray((chull*255).astype(np.uint8)).getbbox()
cropped = Image.fromarray(im).crop(imageBox)
cropped.save('L_2d_cropped.png')
plt.imshow(cropped)
plt.show()

谢谢。

Answer 1

由于两件事，您的图像实际上不是二进制的:

• 首先，它有 26 种颜色，并且
• 其次，它有一个(完全不必要的)alpha channel 。

你可以像这样修剪它:

#!/usr/bin/env python3

from PIL import Image, ImageOps

# Open image and ensure greysale and discard useless alpha channel
im = Image.open("thing.png").convert('L')

# Threshold and invert image as not actually binary
thresh = im.point(lambda p: p < 64 and 255)

# Get bounding box of thresholded image
bbox1 = thresh.getbbox()
crop1 = thresh.crop(bbox1)

# Invert and crop again
crop1n = ImageOps.invert(crop1)
bbox2  = crop1n.getbbox()
crop2  = crop1.crop(bbox2)  # You don't actually need this - it's just for debug

# Trim original, unthresholded, uninverted image to the two bounding boxes
result = im.crop(bbox1).crop(bbox2)
result.save('result.png')