This commit is contained in:
Brian Holt
2012-02-10 15:36:10 -08:00
committed by Stefan van der Walt
parent 96af068860
commit 8f7a2c0743
+5 -6
View File
@@ -4,10 +4,10 @@ Histogram of Oriented Gradients
===============================
The Histogram of Oriented Gradient (HOG) feature descriptor is popular
for object detection
for object detection
<http://en.wikipedia.org/wiki/Histogram_of_oriented_gradients>`__.
In the following example, we compute the HOG descriptor and display
In the following example, we compute the HOG descriptor and display
a visualisation.
Algorithm overview
@@ -19,7 +19,7 @@ Compute a Histogram of Oriented Gradients (HOG) by
3) computing gradient histograms
3) normalising across blocks
4) flattening into a feature vector
The first stage applies an optional global image normalisation
equalisation that is designed to reduce the influence of illumination
effects. In practice we use gamma (power law) compression, either
@@ -27,7 +27,7 @@ computing the square root or the log of each colour channel.
Image texture strength is typically proportional to the local surface
illumination so this compression helps to reduce the effects of local
shadowing and illumination variations.
The second stage computes first order image gradients. These capture
contour, silhouette and some texture information, while providing
further resistance to illumination variations. The locally dominant
@@ -64,7 +64,7 @@ Gradient (HOG) descriptors.
The final step collects the HOG descriptors from all blocks of a dense
overlapping grid of blocks covering the detection window into a combined
feature vector for use in the window classifier.
feature vector for use in the window classifier.
References
----------
@@ -81,7 +81,6 @@ from scikits.image.color import rgb2grey
import numpy as np
import matplotlib.pyplot as plt
# Construct test image
image = data.lena()