从OpenCV中的一维浮点数组计算直方图

Question

我想创建直方图并使用opencv方法cv.CalcHist进行计算。但我的数据是一维数组而不是IplImage对象。为什么下面的代码产生零直方图?:

hist = cv.CreateHist([3, 3], cv.CV_HIST_ARRAY, [[0, 1], [0, 1]]) 
angles, magnitudes = np.random.rand(100), np.random.rand(100) 
cv.CalcHist([cv.GetImage(cv.fromarray(np.array([x]))) for x in [angles, magnitudes]], hist) 
np.array(hist.bins) 

>>> array([[ 0., 0., 0.], 
>>> [ 0., 0., 0.], 
>>> [ 0., 0., 0.]], dtype=float32) 

Answer 1

你上面的代码抛出一个异常（OpenCV的2.3.1）：

OpenCV Error: Unsupported format or combination of formats() in calcHist, file /usr/ports/graphics/opencv-core/work/OpenCV-2.3.1/modules/imgproc/src/histogram.cpp, line 632 
Traceback (most recent call last): 
    File "ocv.py", line 8, in <module> 
cv.CalcHist([cv.GetImage(cv.fromarray(np.array([x]))) for x in [angles, magnitudes]], hist) 
cv2.error 

使用np.float32的角度和幅度修复问题：

hist = cv.CreateHist([3, 3], cv.CV_HIST_ARRAY, [[0, 1], [0, 1]]) 
angles =np.random.rand(100).astype(np.float32)  
magnitude = np.random.rand(100).astype(np.float32) 
cv.CalcHist([cv.GetImage(cv.fromarray(np.array([x]))) for x in [angles, magnitudes]], hist) 
print np.array(hist.bins) 

... 

[[ 11. 9. 7.] 
[ 10. 11. 15.] 
[ 11. 14. 12.]]