diff --git a/doc/examples/plot_thresholding.py b/doc/examples/plot_thresholding.py index a0f7eb08..4def3435 100644 --- a/doc/examples/plot_thresholding.py +++ b/doc/examples/plot_thresholding.py @@ -12,7 +12,9 @@ the threshold. Equivalently, this threshold minimizes the intra-class variance. Additionally an adaptive thresholding is applied. Also known as local or dynamic thresholding where the threshold value is the weighted mean for the -local neighborhood of a pixel subtracted by a constant. +local neighborhood of a pixel subtracted by a constant. Small filter block sizes +are suitable for thresholding edges, large filter block sizes suitable for +thresholding larger homogeneous regions. .. [1] http://en.wikipedia.org/wiki/Otsu's_method @@ -22,35 +24,47 @@ import matplotlib.pyplot as plt import numpy as np from skimage.data import camera -from skimage.filter import threshold_otsu, adaptive_threshold +from skimage.filter import threshold_otsu, threshold_adaptive image = camera() + + +#: Otsu thresholding thresh = threshold_otsu(image) otsu_binary = image > thresh -adaptive_binary = np.invert(adaptive_threshold(image, 9, 5)) -plt.figure(figsize=(8, 2.5)) -plt.subplot(2, 2, 1) +plt.figure(figsize=(8, 6)) +plt.subplot(2, 3, 1) plt.imshow(image, cmap=plt.cm.gray) plt.title('Original') plt.axis('off') -plt.subplot(2, 2, 2, aspect='equal') +plt.subplot(2, 3, 2, aspect='equal') plt.hist(image) plt.title('Histogram') plt.axvline(thresh, color='r') -plt.subplot(2, 2, 3) +plt.subplot(2, 3, 3) plt.imshow(otsu_binary, cmap=plt.cm.gray) plt.title('Thresholded with Otsu') plt.axis('off') -plt.subplot(2, 2, 4) -plt.imshow(adaptive_binary, cmap=plt.cm.gray) -plt.title('Adaptively thresholded') + +#: Adaptive thresholding +plt.subplot(2, 3, 4) +plt.imshow(threshold_adaptive(image, 11, 5, 'gaussian'), cmap=plt.cm.gray) +plt.title('Adaptive edge thresholding') +plt.axis('off') + +plt.subplot(2, 3, 5) +plt.imshow(threshold_adaptive(image, 125, 7.5, 'gaussian'), cmap=plt.cm.gray) +plt.title('Adaptive Gaussian') +plt.axis('off') + +plt.subplot(2, 3, 6) +plt.imshow(threshold_adaptive(image, 125, 7.5, 'mean'), cmap=plt.cm.gray) +plt.title('Adaptive Mean') plt.axis('off') plt.show() - -