Your First Real Project – Live Edge Detection with Recording

Source: Dev.to

Why This Matters

Edge detection is the “hello world” of serious computer vision – it’s where you start tuning parameters, chasing clean lines, and realizing how much time raw OpenCV setups waste.

With vanilla GoCV you’d spend dozens of lines on:

• Camera capture loop
• Window creation
• Mat management (and inevitable leaks)
• Keyboard handling
• Recording logic

GoCVKit gives you all that for free. You focus only on the pipeline.

Hands-On: Build the Edge Detector

Project setup

# If not done yet
mkdir gocvkit-edge && cd gocvkit-edge
go mod init edge-demo
go get github.com/Elliot727/gocvkit

main.go

package main

import (
    "log"
    "github.com/Elliot727/gocvkit"
)

func main() {
    app, err := gocvkit.NewApp("config.toml")
    if err != nil {
        log.Fatal(err)
    }
    defer app.Close()
    app.Run(nil)
}

config.toml

[app]
window_name = "GoCVKit – Live Edge Detection"
record = true                  # Save processed video automatically
output = "edge_detection.mp4"  # Optional: custom filename

[camera]
device_id = 0
# file = "demo.mp4"            # Uncomment to use a video file instead

[stream]
enabled = false                # Keep off for now – we can enable later

[[pipeline.steps]]
name = "Grayscale"

[[pipeline.steps]]
name = "GaussianBlur"
kernel = 9
sigma = 1.8

[[pipeline.steps]]
name = "Canny"
low = 50
high = 150

Run the app

go run .

You should see a live edge‑detection window with:

• Clean Canny edges
• Press f to toggle FPS overlay
• Recording started automatically (edge_detection.mp4)
• Edit any value in config.toml → save → instant update (thanks Week #2!)

Level It Up

Crank the blur for smoother edges

kernel = 15
sigma = 3

Softer edges

low = 30
high = 100

Add morphology to clean up noise

[[pipeline.steps]]
name = "Dilate"
kernel = 3
iterations = 1

Toggle recording live

Flip record = false in config.toml and save.

Bonus: Add a Simple Overlay with Frame Callback

app.Run(func(frame *gocv.Mat) {
    // Runs on the final processed frame
    gocv.PutText(frame, "Low: 50  High: 150", image.Pt(10, 30),
        gocv.FontHersheyPlain, 1.5, gocv.NewScalar(255, 255, 255, 0), 2)
})

(Recompile once – but now you can hot‑reload the text by changing the string or making it config‑driven later.)

Pro Tips

• Recording auto‑rotates files if they get too big – no manual management.
• Press Esc or q to quit gracefully (resources cleaned up).
• Run out of webcam? Swap to a video file by uncommenting file = "demo.mp4".

Try It Yourself

Copy the config.toml above, run the program, and start playing. Break it. Fix it live. Feel the speed.

What’s your favorite edge‑detection tweak? Strong/thin lines or softer outlines? Drop it in the comments!