Please bear with me as this is my first post to stack overflow.
I am attempting to learn rust with a fairly elementary background in OpenCV through python.
In my original python script I could use createTrackbar() pretty easily but when converting to rust I am having trouble understanding how to use the "value", and "on_change" parameters from the Rust OpenCV documentation here
pub fn create_trackbar(
trackbarname: &str,
winname: &str,
value: Option<&mut i32>,
count: i32,
on_change: TrackbarCallback
) -> Result<i32>
My end goal is to then use opencv::highgui::get_trackbar_pos to control Hue max and min, saturation max and min, and value max and min like I do in the python example below:
while True:
cv2.namedWindow("HSV")
cv2.resizeWindow("HSV",640,480)
cv2.createTrackbar("HUE MIN","HSV",0,179,empty)
cv2.createTrackbar("HUE MAX","HSV",0,179,empty)
cv2.createTrackbar("SAT MIN","HSV",0,255,empty)
cv2.createTrackbar("SAT MAX","HSV",0,255,empty)
cv2.createTrackbar("VAL MIN","HSV",0,255,empty)
cv2.createTrackbar("VAL MAX","HSV",0,255,empty)
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
hsvframe = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
h_min = cv2.getTrackbarPos("HUE MIN","HSV")
h_max = cv2.getTrackbarPos("HUE MAX","HSV")
s_min = cv2.getTrackbarPos("SAT MIN","HSV")
s_max = cv2.getTrackbarPos("SAT MAX","HSV")
v_min = cv2.getTrackbarPos("VAL MIN","HSV")
v_max = cv2.getTrackbarPos("VAL MAX","HSV")
lower = np.array([h_min,s_min,v_min])
upper = np.array([h_max,s_max,v_max])
mask = cv2.inRange(hsvframe,lower,upper)
result = cv2.bitwise_and(frame,frame,mask=mask)
print(lower,upper)
out.write(mask)
cv2.imshow('mask',mask)
pass
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
I understand that trackbar name is going to be a string that I choose myself, winname is the hsv window I created, I know count is 179 as I want 180 values from 0 to 179, but don't really understand what Option and TrackbarCallback are supposed to be put in as.
Here is my code below.
use opencv::{ highgui::{self, WINDOW_AUTOSIZE}, imgproc, prelude::*, videoio, Result};
fn run() -> Result<()> {
let window = "video capture";
let hsv = "HSV";
highgui::named_window(window, 1)?;
highgui::named_window(hsv, WINDOW_AUTOSIZE)?;
highgui::create_trackbar("HUE MAX", hsv, )?;
highgui::create_trackbar("HUE MIN", hsv, )?;
opencv::opencv_branch_32! {
let mut cam = videoio::VideoCapture::new_default(0)?; // 0 is the default camera
}
opencv::not_opencv_branch_32! {
let mut cam = videoio::VideoCapture::new(0, videoio::CAP_ANY)?; // 0 is the default camera
}
let opened = videoio::VideoCapture::is_opened(&cam)?;
if !opened {
panic!("Unable to open default camera!");
}
loop {
let mut frame = Mat::default();
cam.read(&mut frame)?;
if frame.size()?.width > 0 {
let mut gray = Mat::default();
imgproc::cvt_color(&frame, &mut gray, imgproc::COLOR_BGR2HSV, 0)?;
highgui::imshow(window, &gray)?;
}
if highgui::wait_key(10)? > 0 {
break;
}
}
Ok(())
}
fn main() {
run().unwrap()
}
As far as I can tell, Option seems to be an arbitrary starting position so I think i32 = 0 could work but I'm not sure, then when going through the TrackbarCallback documentation I'm not sure if I should be putting in the word "pos"
Im sure the answer is rather simple but please understand my exposure is very limited and I am doing my best to learn as much as I can without getting overwhelmed too fast.
If you intend to read the value with get_trackbar_pos, then you can put None for both value and on_change.
In C/C++, value is intended to be a variable in which OpenCV writes the value each time it changes so that you can read it instead of calling get_trackbar_pos. Not sure how that translates to Rust since the existence of a mutable reference to it in OpenCV makes it undefined behaviour to read it elsewhere.
on_change is intended to be the address of a function that OpenCV will call when the value changes, so that you can process the change immediately. You don't need it if you read the value with get_trackbar_pos.