---
title: 'CS362 Assignment #2'
disqus: hackmd
---

線條自畫像 (二值化與邊緣偵測 Image Thresholding and Edge Detection)
===

## 目錄

[TOC]

## 作業說明
撰寫一個程式，以灰階模式讀取一張圖像 imread(path, IMREAD_GRAYSCALE)
(a)利用 Sobel Operators 偵測並輸出邊緣成分圖
(b)設計一個類似素描線條的自畫像圖案。

## 開發環境

$ uname -srvmio
Linux 5.19.0-35-generic #36~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Feb 17 15:17:25 UTC 2 x86_64 x86_64 GNU/Linux
$ gcc --version
gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0
$ pkg-config --modversion opencv4
4.5.4

## 程式碼說明
#### 宣告與初始化變數

// include opencv 與 stdio library
#include "opencv2/highgui.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/photo.hpp"
#include "opencv2/opencv.hpp"
#include <stdio.h>

// 定義GUI視窗名稱、圖片路徑
#define WINDOW_TITLE(...) "Image " __VA_ARGS__
#define FILE_PATH "./fig.jpg"

// 使用 cv namespace 
using namespace cv;

#### 函式宣告

int main()
{
    // load image from path
    Mat src, blur, gray, output_a, output_b1, output_b2; 
    src = imread(FILE_PATH);
    if (src.empty()) {
        printf("%s", "Error loading image \n");
        return -1;
    }
    // convert color image to gray image
    cvtColor(src, gray, COLOR_RGB2GRAY);

    // use blur to reduce noise
    GaussianBlur(gray, blur, Size(7, 7), 0);

    // sobel edge detect
    Sobel(blur, output_a, -1, 1, 1, 5);
    bitwise_not(output_a, output_a);

    // cv2 built-in sketch pencil effect
    pencilSketch(src, output_b1, output_b2, 100, 0.07, 0.07);

    // create window and show output
    namedWindow(WINDOW_TITLE("Edge Detect"), WINDOW_AUTOSIZE);
    imshow(WINDOW_TITLE("Edge Detect"), output_a);
    namedWindow(WINDOW_TITLE("Sketch"), WINDOW_AUTOSIZE);
    imshow(WINDOW_TITLE("Sketch"), output_b1);
    
    // color Sketch 
    // namedWindow(WINDOW_TITLE("Sketch2"), WINDOW_AUTOSIZE);
    // imshow(WINDOW_TITLE("Sketch2"), output_b2);
    waitKey(0);
    return 0;
}

## 程式展示
### 編譯

cmake .
make


### 執行

./HW2


邊緣偵測
素描效果

## 參考資料
[cv::pencilSketch](https://docs.opencv.org/4.7.0/df/dac/group__photo__render.html#gae5930dd822c713b36f8529b21ddebd0c)
[cv:Sobel](https://docs.opencv.org/4.7.0/d4/d86/group__imgproc__filter.html#gacea54f142e81b6758cb6f375ce782c8d)

###### tags: `CS362` `s1081050` `HW2`