获取二维数组中高于某一值的局部最大值的坐标
获取二维数组中高于某一值的局部最大值的坐标
提问于 2012-02-02 19:41:05
from PIL import Image
import numpy as np
from scipy.ndimage.filters import maximum_filter
import pylab
# the picture (256 * 256 pixels) contains bright spots of which I wanna get positions
# problem: data has high background around value 900 - 1000
im = Image.open('slice0000.png')
data = np.array(im)
# as far as I understand, data == maximum_filter gives True-value for pixels
# being the brightest in their neighborhood (here 10 * 10 pixels)
maxima = (data == maximum_filter(data,10))
# How can I get only maxima, outstanding the background a certain value, let's say 500 ?恐怕我不是很了解scipy.ndimage.filters.maximum_filter()函数。有没有一种方法可以只在斑点内而不在背景内获得像素坐标？
http://i.stack.imgur.com/RImHW.png (16位灰度图片，256*256像素)
回答 2
Stack Overflow用户
发布于 2014-03-25 18:22:50
import numpy as np
import scipy
import scipy.ndimage as ndimage
import scipy.ndimage.filters as filters
import matplotlib.pyplot as plt
fname = '/tmp/slice0000.png'
neighborhood_size = 5
threshold = 1500
data = scipy.misc.imread(fname)
data_max = filters.maximum_filter(data, neighborhood_size)
maxima = (data == data_max)
data_min = filters.minimum_filter(data, neighborhood_size)
diff = ((data_max - data_min) > threshold)
maxima[diff == 0] = 0
labeled, num_objects = ndimage.label(maxima)
xy = np.array(ndimage.center_of_mass(data, labeled, range(1, num_objects+1)))
plt.imshow(data)
plt.savefig('/tmp/data.png', bbox_inches = 'tight')
plt.autoscale(False)
plt.plot(xy[:, 1], xy[:, 0], 'ro')
plt.savefig('/tmp/result.png', bbox_inches = 'tight')前面的条目对我非常有用，但是for循环减慢了我的应用程序。我发现ndimage.center_of_mass()在获取坐标方面做得又快又好……因此，提出了这个建议。
Stack Overflow用户
发布于 2017-11-02 00:37:39
现在可以使用skimage来完成此操作。
from skimage.feature import peak_local_max
xy = peak_local_max(data, min_distance=2,threshold_abs=1500)在我的电脑上，对于VGA图像大小，它的运行速度比上面的解决方案快了大约4倍，而且在某些情况下也返回了更准确的位置。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/9111711
复制相关文章
相似问题
腾讯云开发者
