I want to make a simple draw function to draw a line, but I want it to be previewed while it's being drawn; on EVENT_MOUSEMOVE it should draw the line continuously, while not saving it (e.g. how MS paint behaves when you draw a line and can see the output, which is saved when you release the mouse button).
I've used the "more advanced demo" here, where I use the input image as a global, make a copy of it, and then overwrite the image with the copy after drawing, but it doesn't actually make any difference (I neither see the "preview" of the line, and all the lines I draw stay on the canvas) and I can't see why:
img = None
def draw_circle(event,x,y,flags,param):
global ix,iy,drawing,mode,img
img_c = img.copy()
if event == cv2.EVENT_LBUTTONDOWN:
drawing = True
ix,iy = x,y
elif event == cv2.EVENT_MOUSEMOVE:
if drawing == True:
if mode == True:
cv2.line(img,(ix,iy),(x,y),(0,255,0),1)
img = img_c.copy()
else:
cv2.circle(img,(x,y),5,(0,0,255),-1)
elif event == cv2.EVENT_LBUTTONUP:
drawing = False
if mode == True:
cv2.line(img,(ix,iy),(x,y),(0,255,0),1)
else:
cv2.circle(img,(x,y),5,(0,0,255),-1)
while(1):
cv2.imshow('image',img)
k = cv2.waitKey(1) & 0xFF
To preview a line while drawing it, you need to update the image every time you move the mouse, but you need to keep the original to only draw one line. If the line changes orientation the idea is not to draw multiple lines, but to show only one line.
Here is a sample code of what I am talking about. I start with a black canvas, then I preview the line in blue, and once it is finish it becomes green. Read the comments inside the code to understand the details. If you have any questions just comment :)
import numpy as np
import cv2
# create black canvas of size 600x600
img = np.zeros((600, 600, 3), dtype=np.uint8)
# intialize values in unusable states
preview = None
initialPoint = (-1, -1)
# mouse callback
def drawLine(event,x,y,flags,param):
global initialPoint,img, preview
if event == cv2.EVENT_LBUTTONDOWN:
# new initial point and preview is now a copy of the original image
initialPoint = (x,y)
preview = img.copy()
# this will be a point at this point in time
cv2.line(preview, initialPoint, (x,y), (0,255,0), 1)
elif event == cv2.EVENT_MOUSEMOVE:
if preview is not None:
# copy the original image again a redraw the new line
preview = img.copy()
cv2.line(preview, initialPoint, (x,y), (0,255,0), 1)
elif event == cv2.EVENT_LBUTTONUP:
# if we are drawing, preview is not None and since we finish, draw the final line in the image
if preview is not None:
preview = None
cv2.line(img, initialPoint, (x,y), (255,0,0), 1)
# set the named window and callback
cv2.namedWindow("image")
cv2.setMouseCallback("image", drawLine)
while (True):
# if we are drawing show preview, otherwise the image
if preview is None:
cv2.imshow('image',img)
else :
cv2.imshow('image',preview)
k = cv2.waitKey(1) & 0xFF
if k == ord('q'):
break;
cv2.destroyAllWindows()
Related
Here, I have a code that takes a video as input and let the user draw a ROI. Later the cropped video will be displayed. This code was originally taken from I would like to define a Region of Interest in a video and only process that area.
I have provided the code below.
Question: I would like to save the cropped video in .mp4 format. The video output shows only a 1kb file. Can you go through the code and suggest a solution?
NB: I went through answer provided at OpenCV video not getting saved. Still I have failed to figure out the error.
import numpy as np
import cv2
import matplotlib.pyplot as plt
ORIGINAL_WINDOW_TITLE = 'Original'
FIRST_FRAME_WINDOW_TITLE = 'First Frame'
DIFFERENCE_WINDOW_TITLE = 'Difference'
canvas = None
drawing = False # true if mouse is pressed
#Retrieve first frame
def initialize_camera(cap):
_, frame = cap.read()
return frame
# mouse callback function
def mouse_draw_rect(event,x,y,flags, params):
global drawing, canvas
if drawing:
canvas = params[0].copy()
if event == cv2.EVENT_LBUTTONDOWN:
drawing = True
params.append((x,y)) #Save first point
elif event == cv2.EVENT_MOUSEMOVE:
if drawing:
cv2.rectangle(canvas, params[1],(x,y),(0,255,0),2)
elif event == cv2.EVENT_LBUTTONUP:
drawing = False
params.append((x,y)) #Save second point
cv2.rectangle(canvas,params[1],params[2],(0,255,0),2)
def select_roi(frame):
global canvas
#here, it is the copy of the first frame.
canvas = frame.copy()
params = [frame]
ROI_SELECTION_WINDOW = 'Select ROI'
cv2.namedWindow(ROI_SELECTION_WINDOW)
cv2.setMouseCallback(ROI_SELECTION_WINDOW, mouse_draw_rect, params)
roi_selected = False
while True:
cv2.imshow(ROI_SELECTION_WINDOW, canvas)
key = cv2.waitKey(10)
#Press Enter to break the loop
if key == 13:
break;
cv2.destroyWindow(ROI_SELECTION_WINDOW)
roi_selected = (3 == len(params))
print(len(params))
if roi_selected:
p1 = params[1]
p2 = params[2]
if (p1[0] == p2[0]) and (p1[1] == p2[1]):
roi_selected = False
#Use whole frame if ROI has not been selected
if not roi_selected:
print('ROI Not Selected. Using Full Frame')
p1 = (0,0)
p2 = (frame.shape[1] - 1, frame.shape[0] -1)
return roi_selected, p1, p2
if __name__ == '__main__':
cap = cv2.VideoCapture(r'E:\cardiovascular\brad1low.mp4')
#Grab first frame
first_frame = initialize_camera(cap)
#Select ROI for processing. Hit Enter after drawing the rectangle to finalize selection
roi_selected, point1, point2 = select_roi(first_frame)
#Grab ROI of first frame
first_frame_roi = first_frame[point1[1]:point2[1], point1[0]:point2[0]]
print(f'first frame roi is {first_frame_roi}')
#An empty image of full size just for visualization of difference
difference_image_canvas = np.zeros_like(first_frame)
out = cv2.VideoWriter(r'E:\cardiovascular\filename2.mp4', cv2.VideoWriter_fourcc(*'MP4V'), int(cap.get(cv2.CAP_PROP_FRAME_COUNT)), (int(first_frame_roi.shape[0]), (int(first_frame_roi.shape[1]))))
while cap.isOpened():
ret, frame = cap.read()
if ret:
#ROI of current frame
roi = frame[point1[1]:point2[1], point1[0]:point2[0]]
print(f'roi is {roi}')
cv2.imshow(DIFFERENCE_WINDOW_TITLE, roi)
out.write(roi)
key = cv2.waitKey(30) & 0xff
if key == 27:
break
else:
break
cap.release()
out.release()
cv2.destroyAllWindows()
appreciate if anyone can help tyring to select an ROI on a video stream while it's playing (don't want it to pause or capture the first frame)
am I missing something, I've tried setting to the frames to the same name
cv2.selectROI('Frame', frame, False)
cv2.imshow('Frame',frame)
Thanks
You can't use cv2.selectROI() in that case because the function is blocking, i.e. it stops the execution of your program until you have selected your region of interest (or cancelled it).
To achieve what you want you will need to handle the selection of the ROI yourself. Here is a short example of how you can do that, using two left-clicks to define the ROI and a right-click to erase it.
import cv2, sys
cap = cv2.VideoCapture(sys.argv[1])
cv2.namedWindow('Frame', cv2.WINDOW_NORMAL)
# Our ROI, defined by two points
p1, p2 = None, None
state = 0
# Called every time a mouse event happen
def on_mouse(event, x, y, flags, userdata):
global state, p1, p2
# Left click
if event == cv2.EVENT_LBUTTONUP:
# Select first point
if state == 0:
p1 = (x,y)
state += 1
# Select second point
elif state == 1:
p2 = (x,y)
state += 1
# Right click (erase current ROI)
if event == cv2.EVENT_RBUTTONUP:
p1, p2 = None, None
state = 0
# Register the mouse callback
cv2.setMouseCallback('Frame', on_mouse)
while cap.isOpened():
val, frame = cap.read()
# If a ROI is selected, draw it
if state > 1:
cv2.rectangle(frame, p1, p2, (255, 0, 0), 10)
# Show image
cv2.imshow('Frame', frame)
# Let OpenCV manage window events
key = cv2.waitKey(50)
# If ESCAPE key pressed, stop
if key == 27:
cap.release()
I'm using Python3 and OpenCV (4.1.0) to realize a script that:
displays the contents of the webcam;
records the coordinates of mouse clicks over video;
after pressing a certain button ('p' in my example), draws a polyline between the points identified by previous mouse clicks;
So far, I'm trying:
import numpy as np
import cv2
def main():
cap = cv2.VideoCapture("files/long_video.mp4") # Open video file
points = []
while (cap.isOpened()):
ret, frame = cap.read() # read a frame
try:
cv2.imshow('Frame', frame)
except:
print('EOF')
break
cv2.setMouseCallback('Frame', left_click_detect, points)
# Abort and exit with 'Q'
key = cv2.waitKey(25)
if (key == ord('q')):
break
elif (key== ord('p')): # HERE, IT SHOULD DRAW POLYLINE OVER VIDEO!!!
pts_array = np.array([[x, y] for (x, y) in points], np.int0)
frame = cv2.polylines(frame, np.int32(np.array(points)), False, (255, 0, 0), thickness=5)
points = []
cv2.imshow('Frame', frame)
cap.release() # release video file
cv2.destroyAllWindows() # close all openCV windows
def left_click(event, x, y, flags, points):
if (event == cv2.EVENT_LBUTTONDOWN):
print(f"\tClick on {x}, {y}")
points.append([x,y])
It kinda works, but after pressing 'p' it doesn't draw the polyline over the video.
Any suggestions?
There are 2 problems with your code:
cv2.polylines() accepts a list of arrays. so here:
frame = cv2.polylines(frame, np.int32(np.array(points)), False, (255, 0, 0), thickness=5)
Replace np.int32(np.array(points)) with [np.int32(points)] to fix the exception. (you also don't need to use np.array() here)
After you draw the polygon on the frame, you call cv2.show(), but almost immediately after, you show the next frame without the polygon on it, so you don't have time to see the polygon. to fix it you need to draw the polygon again for each frame. and to do that, you need to save it until you press p again (to show another polygon).
This will work:
import numpy as np
import cv2
def main():
cap = cv2.VideoCapture("files/long_video.mp4") # Open video file
polygon = []
points = []
while (cap.isOpened()):
ret, frame = cap.read() # read a frame
if not ret:
print('EOF')
break
frame = cv2.polylines(frame, polygon, False, (255, 0, 0), thickness=5)
cv2.imshow('Frame', frame)
# Abort and exit with 'Q'
key = cv2.waitKey(25)
if (key == ord('q')):
break
elif (key== ord('p')):
polygon = [np.int32(points)]
points = []
cv2.setMouseCallback('Frame', left_click_detect, points)
cap.release() # release video file
cv2.destroyAllWindows() # close all openCV windows
def left_click_detect(event, x, y, flags, points):
if (event == cv2.EVENT_LBUTTONDOWN):
print(f"\tClick on {x}, {y}")
points.append([x,y])
print(points)
I am trying to implement a robotic solution, where the user will click on a point through a camera feed of an area and the mobile 4 wheel robot will path its way to that location.
I have created the part of translating video pixel coordinates to ground coordinates through the use of the homograph transformation and would like to implement the part of sending the ground coordinates to RViz.
The part of calculating the ground coordinates is shown bellow:
global h
font = cv2.FONT_HERSHEY_SIMPLEX #Loading neccessary fonts
with open("save.h", "rb") as f:
h = load(f)
print "Homographic matrix loaded successfully."
def draw_circle2(event,x,y,flags,param):
global h,mouseX,mouseY, num_of_points, complete,np_coord_on_screen,np_coord_on_ground, myImage, emptyFrame, coord_on_screen, coord_on_ground
if event == cv2.EVENT_LBUTTONDBLCLK:
a = np.array([[x, y]], dtype='float32')
a = np.array([a])
pointOut = cv2.perspectiveTransform(a, h) #Calculation of new point location
loc_pointOut = tuple(pointOut)
pointOut=(loc_pointOut[0][0][0],loc_pointOut[0][0][1]) #Point on ground
print "Current Location: "+str(pointOut)
cv2.imshow('Video',emptyFrame) #Showing emptyFrame
cv2.circle(myImage,(x,y),4,(255,0,0),-1) #Draw a circle on myImage
cv2.putText(myImage,(str((round(pointOut[0],2)))+","+str(round(pointOut[1],2))), (x-5,y-15),font, 0.4,(0,255,0)) #Draw the text
cv2.imshow('Video',myImage) #Showing resulting myImage
myImage = emptyFrame.copy()
# Initial code
# Showing first frame on screen
raw_input("Press any key...")
clear_all()
cv2.namedWindow('Video') #Naming the window to use.
cv2.setMouseCallback('Video',draw_circle2) #Set mouse callBack function.
ret, frame = cap.read() #Get image from camera
if (ret): #If frame has image, show the image on screen
global myImage, emptyFrame
myImage = frame.copy()
emptyFrame = frame.copy()
cv2.imshow('Video',myImage) # Show the image on screen
while True: # making a loop
if cv2.waitKey(1) & 0xFF == ord('q'):
break
if (cv2.waitKey(1) & 0xFF == ord('c')):
#Deleting points from image
cv2.imshow('Video',emptyFrame) #Show the image again, deleting all graphical overlays like text and shapes
coord_on_screen = [] #Resetting coordinate lists
coord_on_ground=[] #Resetting coordinate lists
if (cv2.waitKey(1) & 0xFF == ord('s')):
cap.release()
cv2.destroyAllWindows()
init()
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()
So, pointOut is the point on the ground (example: (2,4) m)
I need some directions on how to implement the creation of a node and the transmission of the pointOut Marker message to a ROS topic in my code.
My configuration is ROS Kinetic Kame, Python 2.7
In my code after certain time (depend of the PC or OS) crashes. The error displayed is
libpng warning: Image width is zero in IHDR
libpng warning: Image height is zero in IHDR
libpng error: Invalid IHDR data
My code draw ROI on a video from webcam and take a snapshot. The ROI is deleted after 5-10 minutes (I'm not sure why, this is the error) and the picture saved not have dimensions then the error above is displayed but I'm not find the error. The instructions are, press "c" to stop the video and draw a ROI, press again "c" to take the picture, press "r" to resume the video, and repeat if you need another pictures.
I tested the code in Windows 10 and raspbian on a raspberry and the time is not the same but on both the program crashes. This is my code:
import cv2
# python PSI_Camera_test.py
class staticROI(object):
def __init__(self):
self.capture = cv2.VideoCapture(0)
self.capture.set(cv2.CAP_PROP_FRAME_WIDTH, 1280)
self.capture.set(cv2.CAP_PROP_FRAME_HEIGHT, 720)
# Bounding box reference points and boolean if we are extracting coordinates
self.image_coordinates = []
self.extract = False
self.selected_ROI = False
self.img_counter = 0
self.update()
def update(self):
while True:
if self.capture.isOpened():
# Read frame
(self.status, self.frame) = self.capture.read()
cv2.imshow('image', self.frame)
key = cv2.waitKey(2)
# Crop image
if key == ord('c'):
self.clone = self.frame.copy()
cv2.namedWindow('image')
cv2.setMouseCallback('image', self.extract_coordinates)
while True:
key = cv2.waitKey(2)
cv2.imshow('image', self.clone)
# Crop and display cropped image
if key == ord('c'):
self.crop_ROI()
img_name = "Images\opencv_frame_{}.png".format(
self.img_counter)
cv2.imwrite(img_name, self.cropped_image)
print("{} written!".format(img_name))
self.img_counter += 1
# Resume video
if key == ord('r'):
break
# Close program with keyboard 'esp'
if key % 256 == 27:
cv2.destroyAllWindows()
exit(1)
else:
pass
def extract_coordinates(self, event, x, y, flags, parameters):
# Record starting (x,y) coordinates on left mouse button click
if event == cv2.EVENT_LBUTTONDOWN:
self.image_coordinates = [(x, y)]
self.extract = True
# Record ending (x,y) coordintes on left mouse bottom release
elif event == cv2.EVENT_LBUTTONUP:
self.image_coordinates.append((x, y))
self.extract = False
self.selected_ROI = True
# Draw rectangle around ROI
cv2.rectangle(
self.clone, self.image_coordinates[0], self.image_coordinates[1], (0, 255, 0), 2)
# Clear drawing boxes on right mouse button click
elif event == cv2.EVENT_RBUTTONDOWN:
self.clone = self.frame.copy()
self.selected_ROI = False
def crop_ROI(self):
if self.selected_ROI:
self.cropped_image = self.frame.copy()
x1 = self.image_coordinates[0][0]
y1 = self.image_coordinates[0][1]
x2 = self.image_coordinates[1][0]
y2 = self.image_coordinates[1][1]
self.cropped_image = self.cropped_image[y1:y2, x1:x2]
print('Cropped image: {} {}'.format(
self.image_coordinates[0], self.image_coordinates[1]))
else:
print('Select ROI to crop before cropping')
# python PSI_Camera_test.py
if __name__ == '__main__':
static_ROI = staticROI()
Thanks in advance!