I want to find contours in an image and further process them e.g. drawing them on the image.
To do that I have two functions running in different threads:
storage = cv.CreateMemStorage(0)
contour = cv.FindContours(inData.content, storage, cv.CV_RETR_EXTERNAL, cv.CV_CHAIN_APPROX_SIMPLE)
and
while contours:
bound_rect = cv.BoundingRect(list(contours))
contours = contours.h_next()
pt1 = (bound_rect[0], bound_rect[1])
pt2 = (bound_rect[0] + bound_rect[2], bound_rect[1] + bound_rect[3])
cv.Rectangle(inImg.content, pt1, pt2, cv.CV_RGB(255,0,0), 1)
Each function runs in a loop processing one image after the other.
When a function is done it puts the image in a buffer from which the other function can get it.
This works except that in the result the contours are drawn in the image one or two images before their corresponding image.
I think this has something to do with the storage of OpenCV but I don’t understand why the storage is needed and what it does
EDIT Here is some more code:
My program is meant to be a node based image analasys software.
This is how the node graph of my current code looks like:
|---------| |--------|
|-----| |-----|------>|Threshold|--->|Contours|--->|-------------| |------|
|Input|--->|Split| |---------| |--------| |Draw Contours|--->|Output|
|-----| |-----|----------------------------------->|-------------| |------|
This is the class from which all nodes derive:
from Buffer import Buffer
from threading import Thread
from Data import Data
class Node(Thread):
def __init__(self, inputbuffers, outputbuffers):
Thread.__init__(self)
self.inputbuffers = inputbuffers
self.outputbuffers = outputbuffers
def getInputBuffer(self, index):
return self.inputbuffers[index]
def getOutputBuffer(self, index):
return self.outputbuffers[index]
def _getContents(self, bufferArray):
out = []
for bufferToGet in bufferArray:
if bufferToGet and bufferToGet.data:
out.append(bufferToGet.data)
for bufferToGet in bufferArray:
bufferToGet.data = None
return out
def _allInputsPresent(self):
for bufferToChk in self.inputbuffers:
if not bufferToChk.data:
return False
return True
def _allOutputsEmpty(self):
for bufferToChk in self.outputbuffers:
if bufferToChk.data != None:
return False
return True
def _applyOutputs(self, output):
for i in range(len(output)):
if self.outputbuffers[i]:
self.outputbuffers[i].setData(output[i])
def run(self):
#Thread loop <------------------------------------
while True:
while not self._allInputsPresent(): pass
inputs = self._getContents(self.inputbuffers)
output = [None]*len(self.outputbuffers)
self.process(inputs, output)
while not self._allOutputsEmpty(): pass
self._applyOutputs(output)
def process(self, inputs, outputs):
'''
inputs: array of Data objects
outputs: array of Data objects
'''
pass
The nodes pass around these Data objects:
class Data(object):
def __init__(self, content = None, time = None, error = None, number = -1):
self.content = content #Here the actual data is stored. Mostly images
self.time = time #Not used yet
self.error = error #Not used yet
self.number = number #Used to see if the correct data is put together
This are the nodes:
from Node import Node
from Data import Data
import copy
import cv
class TemplateNode(Node):
def __init__(self, inputbuffers, outputbuffers):
super(type(self), self).__init__(inputbuffers, outputbuffers)
def process(self, inputs, outputs):
inData = inputs[0]
#Do something with the content e.g.
#cv.Smooth(inData.content, inData.content, cv.CV_GAUSSIAN, 11, 11)
outputs[0] = inData
class InputNode(Node):
def __init__(self, inputbuffers, outputbuffers):
super(InputNode, self).__init__(inputbuffers, outputbuffers)
self.capture = cv.CaptureFromFile("video.avi")
self.counter = 0
def process(self, inputs, outputs):
image = cv.QueryFrame(self.capture)
if image:
font = cv.InitFont(cv.CV_FONT_HERSHEY_SIMPLEX, 1, 1, 0, 3, 8)
x = 30
y = 50
cv.PutText(image, str(self.counter), (x,y), font, 255)
outputs[0] = Data(image,None,None,self.counter)
self.counter = self.counter+1
class OutputNode(Node):
def __init__(self, inputbuffers, outputbuffers, name):
super(type(self), self).__init__(inputbuffers, outputbuffers)
self.name = name
def process(self, inputs, outputs):
if type(inputs[0].content) == cv.iplimage:
cv.ShowImage(self.name, inputs[0].content)
cv.WaitKey()
class ThresholdNode(Node):
def __init__(self, inputbuffers, outputbuffers):
super(type(self), self).__init__(inputbuffers, outputbuffers)
def process(self, inputs, outputs):
inData = inputs[0]
inimg = cv.CreateImage(cv.GetSize(inData.content), cv.IPL_DEPTH_8U, 1);
cv.CvtColor(inData.content, inimg, cv.CV_BGR2GRAY)
outImg = cv.CreateImage(cv.GetSize(inimg), cv.IPL_DEPTH_8U, 1);
cv.Threshold(inimg, outImg, 70, 255, cv.CV_THRESH_BINARY_INV);
inData.content = outImg
outputs[0] = inData
class SplitNode(Node):
def __init__(self, inputbuffers, outputbuffers):
super(type(self), self).__init__(inputbuffers, outputbuffers)
def process(self, inputs, outputs):
inData = inputs[0]
if type(inData.content) == cv.iplimage:
imagecpy = cv.CloneImage(inData.content)
outputs[1] = Data(imagecpy, copy.copy(inData.time), copy.copy(inData.error), copy.copy(inData.number))
else:
outputs[1] = copy.deepcopy(inData)
print
class ContoursNode(Node):
def __init__(self, inputbuffers, outputbuffers):
super(type(self), self).__init__(inputbuffers, outputbuffers)
def process(self, inputs, outputs):
inData = inputs[0]
storage = cv.CreateMemStorage(0)
contours = cv.FindContours(inData.content, storage, cv.CV_RETR_EXTERNAL, cv.CV_CHAIN_APPROX_SIMPLE)
contoursArr = []
while contours:
points = []
for (x,y) in contours:
points.append((x,y))
contoursArr.append(points)
contours = contours.h_next()
outputs[0] = Data(contoursArr, inData.time, inData.error, inData.number)
pass
class DrawContoursNode(Node):
def __init__(self, inputbuffers, outputbuffers):
super(type(self), self).__init__(inputbuffers, outputbuffers)
def process(self, inputs, outputs):
inImg = inputs[0]
contours = inputs[1].content
print "Image start"
for cont in contours:
for (x,y) in cont:
cv.Circle(inImg.content, (x,y), 2, cv.CV_RGB(255, 0, 0))
print "Image end"
outputs[0] = inImg
This is the main function. Here all the nodes and buffers are created.
from NodeImpls import *
from Buffer import Buffer
buffer1 = Buffer()
buffer2 = Buffer()
buffer3 = Buffer()
buffer4 = Buffer()
buffer5 = Buffer()
buffer6 = Buffer()
innode = InputNode([], [buffer1])
split = SplitNode([buffer1], [buffer2, buffer3])
thresh = ThresholdNode([buffer3], [buffer4])
contours = ContoursNode([buffer4], [buffer5])
drawc = DrawContoursNode([buffer2, buffer5],[buffer6])
outnode = OutputNode([buffer6], [], "out1")
innode.start()
split.start()
thresh.start()
contours.start()
drawc.start()
outnode.start()
while True:
pass
The buffer:
class Buffer(object):
def __init__(self):
self.data = None
def setData(self, data):
self.data = data
def getData(self):
return self.data
Storage is just a place to keep the results. OpenCV is a C++ library, and relies on manual memory allocation, C++ style. Python bindings are just a thin wrapper around it, and are not very pythonic. That’s why you have to allocate storage manually, like if you did it in C or in C++.
I assume your threads are not properly synchronized. This problem is not likely to be related to OpenCV, but to what functions you have, what data they use and pass around, and how you share the data between them.
In short, please post your code where you create threads and call these functions, as well where
inImg,inData,contour,contoursandstorageare accessed or modified.