Python中的OpenCV PCA计算 [英] OpenCV PCA Compute in Python

问题描述

我正在通过OpenCV(在Python中)加载一组尺寸为128x128的测试图像，将它们重新整形为矢量(1、128x128)，然后将它们全部放到一个矩阵中以计算PCA.我正在使用新的cv2库...

I'm loading a set of test images via OpenCV (in Python) which are 128x128 in size, reshape them into vectors (1, 128x128) and put them all together in a matrix to calculate PCA. I'm using the new cv2 libaries...

代码:

import os
import cv2 as cv
import numpy as np

matrix_test = None
for image in os.listdir('path_to_dir'):
    imgraw = cv.imread(os.path.join('path_to_dir', image), 0)
    imgvector = imgraw.reshape(128*128)
    try:
        matrix_test = np.vstack((matrix_test, imgvector))
    except:
        matrix_test = imgvector

# PCA
mean, eigenvectors = cv.PCACompute(matrix_test, np.mean(matrix_test, axis=0))

在PCA部分上它总是失败(我测试了图像加载，所有结果矩阵就是它应该的样子)...我得到的错误是:

And it allways fails on the PCA part (I tested the image loading and all, the resulting matrix is how it should be)...the error I get is:

平均值，特征向量= cv.PCACompute(matrix_test，np.mean(matri_test，axis = 0))

mean, eigenvectors = cv.PCACompute(matrix_test, np.mean(matri_test, axis=0))

cv2.error:/path/to/OpenCV-2.3.1/modules/core/src/matmul.cpp:2781:错误:(-215)_mean.size()==函数操作符()中的mean_sz

cv2.error: /path/to/OpenCV-2.3.1/modules/core/src/matmul.cpp:2781: error: (-215) _mean.size() == mean_sz in function operator()

推荐答案

我认为问题在于

np.mean(matrix_test, axis=0)

它的大小是(128x128)，而不是(1，128x128).因此，下面的代码应该可以工作

Its size is (128x128,) and not (1, 128x128). Thus the code below should work

mean, eigenvectors = cv.PCACompute(matrix_test, np.mean(matrix_test, axis=0).reshape(1,-1))

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