Develop Reference

Opencv Error:(-215)

I am writing this simple code but this is showing error saying size.width>0&&size.height>0 in function imshow()enter code here
import numpy as np
import cv2
img = cv2.imread('C:/Users/Desktop/x.jpg',0)
cv2.namedWindow('image',cv2.WINDOW_NORMAL)
cv2.imshow('image',img)
cv2.namedWindow('image',cv2.WINDOW_NORMAL)
cv2.waitKey(0)
cv2.destroyAllWindows()

Assuming you are using Windows, write path name as:
img = cv2.imread('C:\\Users\\Desktop\\x.jpg', 0)
to load the image correctly.

How to import png images Python

I've tried to import a png file in Python 3.6 with Jupyter Notebook with no success.
I've seen some examples that don't work, at least not anymore, i.e.
import os,sys
import Image
jpgfile = Image.open("picture.jpg")
There is no module called Image that I can install with either:
conda install Image
or
pip install Image
Any simple solution would be greatly appreciated!

You can display an image from file in a Jupyter Notebook as follows:
from IPython.display import Image
img = 'fig31_Drosophila.jpg'
Image(url=img)
where img = 'fig31_Drosophila.jpg' is the path and filename of the image you want. (here, the image is in the same folder as the main script)
alternatively:
from IPython.display import Image
img = 'fig31_Drosophila.jpg'
Image(filename=img)
You can specify optional args (for width and height for instance:
from IPython.display import Image
img = 'fig31_Drosophila.jpg'
Image(url=img, width=100, height=100)

opencv-3.0.0 on Raspberry error

HI i have this error in Opencv-3.0.0 on rasperry Pi
enter cod# OpenCV_test1.py
this program opens the file in the same directory names "image.jpg" and displays the original image and a Canny edges of the original image
import cv2
import numpy as np
import os
#
def main():
imgOriginal = cv2.imread("image.jpg") # open image
if imgOriginal is None: # if image was not read successfully
print "error: image not read from file \n\n" # print error message to std out
os.system("pause") # pause so user can see error message
return # and exit function (which exits program)
# end if
imgGrayscale = cv2.cvtColor(imgOriginal, cv2.COLOR_BGR2GRAY) # convert to grayscale
imgBlurred = cv2.GaussianBlur(imgGrayscale, (5, 5), 0) # blur
imgCanny = cv2.Canny(imgBlurred, 100, 200) # get Canny edges
cv2.namedWindow("imgOriginal", cv2.WINDOW_AUTOSIZE) # create windows, use WINDOW_AUTOSIZE for a fixed window size
cv2.namedWindow("imgCanny", cv2.WINDOW_AUTOSIZE) # or use WINDOW_NORMAL to allow window resizing
cv2.imshow("imgOriginal", imgOriginal) # show windows
cv2.imshow("imgCanny", imgCanny)
cv2.waitKey() # hold windows open until user presses a key
cv2.destroyAllWindows() # remove windows from memory
return
#
if name == "main":
main()
e here
and this is the Error
python OpenCV_test1.py
File "OpenCV_test1.py", line 4
import cv2 import numpy as np import os
^
SyntaxError: invalid syntax

Imports must go on separate rows (or be be separated by semicolons, but please don't).
Change
import cv2 import numpy as np import os
to
import cv2
import numpy as np
import os

cv2 equivalent attributes to cv

I have come across this link for face detection and image cropping. I would like to use this script but I have cv2 install and only import cv2 works but not import cv.
How can I convert the cv functions in the following function to cv2 functions?
def faces_from_pil_image(pil_image):
"Return a list of (x,y,h,w) tuples for faces detected in the PIL image"
storage = cv.CreateMemStorage(0)
facial_features = cv.Load('haarcascade_frontalface_alt.xml', storage=storage)
cv_im = cv.CreateImageHeader(pil_image.size, cv.IPL_DEPTH_8U, 3)
cv.SetData(cv_im, pil_image.tostring())
faces = cv.HaarDetectObjects(cv_im, facial_features, storage)
# faces includes a `neighbors` field that we aren't going to use here
return [f[0] for f in faces]

Either use
import cv2
storage = cv2.cv.CreateMemStorage(0)
or
from cv2 import *
storage = cv.CreateMemStorage(0)

opencv python face detection from url images

I have no problem getting the opencv face detection using haar feature based cascades working on saved images:
from PIL import Image
face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')
img = cv2.imread('pic.png')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
faces = face_cascade.detectMultiScale(gray, 1.3, 5)
but I can't figure out how to open a url image and pass it into face_cascade. I've been playing around with cStringIO, but I don't know what to do with it...
import cv2.cv as cv
import urllib, cStringIO
img = 'http://scontent-b.cdninstagram.com/hphotos-prn/t51.2885-15/10424498_582114441904402_1105042543_n.png'
file = cStringIO.StringIO(urllib.urlopen(img).read())
source = Image.open(file).convert("RGB")
bitmap = cv.CreateImageHeader(source.size, cv.IPL_DEPTH_8U, 3)
cv.SetData(bitmap, source.tostring())
cv.CvtColor(bitmap, bitmap, cv.CV_RGB2BGR)
is it possible to work with a numpy array instead?
source2 = Image.open(file)
imarr=numpy.array(source2,dtype=numpy.uint8)
I'm a beginner, so I apologize for the poor explanation.
thanks a lot in advance!!

In your first example you are using OpenCV2.imread to read your image in the second you are presumably using PIL.Image then trying to convert.
Why not simply save the file to a temp directory and then use OpenCV2.imread again?

Or in another way you can use VideoCapture() class to open url image.
See the C++ code below,
VideoCapture cap;
if(!cap.open("http://docs.opencv.org/trunk/_downloads/opencv-logo.png")){
cout<<"Cannot open image"<<endl;
return -1;
}
Mat src;
cap>>src;
imshow("src",src);
waitKey();