Question

我想使用选择性搜索算法将图像分割成可能的对象位置。我发现我已经用于计算机视觉的库OpenCV实现了这个功能，如文档here所示。但是，我使用的是Python而不是C ++，所以我查看了OpenCV的github存储库，直到找到我在下面复制的example。

#!/usr/bin/env python

'''
A program demonstrating the use and capabilities of a particular image segmentation algorithm described
in Jasper R. R. Uijlings, Koen E. A. van de Sande, Theo Gevers, Arnold W. M. Smeulders:
    "Selective Search for Object Recognition"
International Journal of Computer Vision, Volume 104 (2), page 154-171, 2013
Usage:
    ./selectivesearchsegmentation_demo.py input_image (single|fast|quality)
Use "a" to display less rects, 'd' to display more rects, "q" to quit.
'''

import cv2
import sys

if __name__ == '__main__':
    img = cv2.imread(sys.argv[1])

    cv2.setUseOptimized(True)
    cv2.setNumThreads(8)

    gs = cv2.ximgproc.segmentation.createSelectiveSearchSegmentation()
    gs.setBaseImage(img)

    if (sys.argv[2][0] == 's'):
        gs.switchToSingleStrategy()

    elif (sys.argv[2][0] == 'f'):
        gs.switchToSelectiveSearchFast()

    elif (sys.argv[2][0] == 'q'):
        gs.switchToSelectiveSearchQuality()
    else:
        print(__doc__)
        sys.exit(1)

    rects = gs.process()
    nb_rects = 10

    while True:
        wimg = img.copy()

        for i in range(len(rects)):
            if (i < nb_rects):
                x, y, w, h = rects[i]
                cv2.rectangle(wimg, (x, y), (x+w, y+h), (0, 255, 0), 1, cv2.LINE_AA)

        cv2.imshow("Output", wimg);
        c = cv2.waitKey()

        if (c == 100):
            nb_rects += 10

        elif (c == 97 and nb_rects > 10):
            nb_rects -= 10

        elif (c == 113):
            break

    cv2.destroyAllWindows()

不幸的是，使用命令python selective_search.py "/home/christopher/DroneKit/Vision/Face Detection/Annotated Faces in the Wild/originalPics/2002/07/19/big/img_135.jpg" f运行此程序会出现以下错误：

Traceback (most recent call last):
  File "selective_search.py", line 37, in <module>
    rects = gs.process()
TypeError: Required argument 'rects' (pos 1) not found

根据该错误消息，我想也许我可以将它传递给Python列表，然后底层的C ++函数会用算法的输出填充它。但是，当我执行以下代码时：

rects = []
gs.process(rects)
print(rects)

输出为空列表，显示的图像上没有绘制矩形。因此，我对如何拨打gs.process()感到茫然。如果有帮助，函数的C ++声明是

CV_WRAP virtual void process(CV_OUT std::vector<Rect>& rects) = 0;

（编辑）从评论中复制的其他信息：

help(gs.process)的输出：

process(...) method of cv2.ximgproc_segmentation_SelectiveSearchSegmentation instance process(rects) -> None. rects = gs.process(rects) just makes rects None and causes the program to terminate with an exception

使用rects = gs.process(rects)设置rects到None并导致程序以异常终止。

OpenCV版本是3.2.0。

使用numpy数组而不是python列表会崩溃我的程序，并显示以下消息：

OpenCV Error: Assertion failed (channels() == CV_MAT_CN(dtype)) in copyTo, file /home/christopher/opencv/modules/core/src/copy.cpp, line 259
terminate called after throwing an instance of 'cv::Exception'
  what():  /home/christopher/opencv/modules/core/src/copy.cpp:259: error: (-215) channels() == CV_MAT_CN(dtype) in function copyTo

Aborted (core dumped)

Answer 1

显然，我为Python编译的OpenCV 3.2.0版本在本地缺少此fix。我继续使用OpenCV 3.3.0的latest stable release重新编译我的python绑定，并对OpenCV contrib存储库进行了最新更改，之后示例脚本按预期工作。

从Python调用这个OpenCV函数的正确方法是什么？

1 个答案: