如何在python中使用opencv处理图像？

我想使用 opencv 库中的边缘检测算法。 这是一段Python代码：

from opencv.cv import *
from opencv.highgui import *

img = cvLoadImage ('xxx.jpg')
cvNamedWindow ('img')
cvShowImage ('img', img)
cvWaitKey ()

canny = cvCreateImage (cvSize (img.width, img.height), 8, 3)
cvCanny (img, canny, 50, 200)

harris = cvCreateImage (cvSize (img.width, img.height), 8, 3)
cvCornerHarris (img, harris, 5, 5, 0.1)

加载和显示图像工作正常，但精明和哈里斯转换失败。
cvCanny失败并显示：

RuntimeError:  openCV Error:
    Status=Unsupported format or combination of formats
    function name=cvCanny
    error message=
    file_name=cv/cvcanny.cpp
    line=72

and cvCornerHarris失败并出现此错误：

RuntimeError:  openCV Error:
    Status=Assertion failed
    function name=cvCornerHarris
    error message=src.size() == dst.size() && dst.type() == CV_32FC1
    file_name=cv/cvcorner.cpp
    line=370

从这条消息我可以推断加载的图像格式无效。但我不明白如何转换它。
这是一些值img fields:

img.type = 1111638032
img.nChannels = 3
img.depth = 8

对于对同一类型问题感兴趣的其他人，我建议查看http://simplecv.org http://simplecv.org

Here is a bit of code I wrote that does line detection on an image acquired from a webcam. It will even display the image over http.

import SimpleCV
import time

c = SimpleCV.Camera(1)
js = SimpleCV.JpegStreamer() 

while(1):
  img = c.getImage()
  img = img.smooth()
  lines = img.findLines(threshold=25,minlinelength=20,maxlinegap=20)
  [line.draw(color=(255,0,0)) for line in lines]
  #find the avg length of the lines
  sum = 0
  for line in lines:
      sum = line.length() + sum
  if sum:
      print sum / len(lines)
  else:
      print "No lines found!"
  img.save(js.framebuffer)
  time.sleep(0.1)

查看我为此所做的项目http://labs.radiantmachines.com/beard/ http://labs.radiantmachines.com/beard/它会检测你脖子上的胡须有多长:)