在图像处理领域，线条检测是一项基础而重要的任务，它在医学影像分析、文本提取、图像检查等多个领域都有广泛的应用。本文介绍的算法能够从图像中检测线条，并计算出线条的角度。虽然存在多种高级算法可以实现这一功能，但本文介绍的是一种简单且易于实现的方法。
该算法具有以下特点：
源代码中包含了详细的注释，首先定义一个全局的图像对象，然后从硬盘加载图像文件：
CImage i;
接下来，需要在OnPaint()函数中绘制图像：
void CDetectangleoflineDlg::OnPaint() {
if (!i.IsNull()) {
CClientDC dc(this);
i.BitBlt(dc.m_hDC, 0, 0, SRCCOPY);
}
}
然后，加载图像：
void CDetectangleoflineDlg::OnBnClickedButton1() {
CFileDialog f(1);
TCHAR tc[260];
CString s;
GetCurrentDirectory(260, tc);
s = tc;
if (f.DoModal() == IDOK) {
if (!i.IsNull()) {
i.Destroy();
i.Load(f.GetFolderPath() + _T("\\") + f.GetFileName());
OnPaint();
b.EnableWindow(1);
}
}
}
最后，使用Process算法来确定角度：
void CDetectangleoflineDlg::OnBnClickedButton2() {
CImage i1;
i1 = i;
CDC cdc;
cdc.Attach(i1.GetDC());
CPen p(PS_SOLID, 1, RGB(255, 255, 0)), p1(PS_SOLID, 1, RGB(0, 0, 255));
cdc.SelectObject(&p);
register int x1, x2, y1, y2;
x1 = x2 = y1 = y2 = -1;
double pi = 3.1415926535;
register long r, g, b, r1, g1, b1;
register COLORREF c, c1;
register int tol = 30, d = 20;
c = i1.GetPixel(0, 0);
r = GetRValue(c);
g = GetGValue(c);
b = GetBValue(c);
bool ar[600][450];
for (register int y = 0; y < i.GetHeight(); y++) {
for (register int x = 0; x < i.GetWidth(); x++) {
ar[y][x] = 0;
}
}
for (register int y = 0; y < i.GetHeight(); y++) {
for (register int x = 0; x < i.GetWidth(); x++) {
c1 = i.GetPixel(x, y);
r1 = GetRValue(c1);
g1 = GetGValue(c1);
b1 = GetBValue(c1);
if ((abs(r - r1) > tol) && (abs(g - g1) > tol) && (abs(b - b1) > tol)) {
ar[y][x] = 1;
} else {
ar[y][x] = 0;
}
}
}
for (register int y = 0; y < i.GetHeight(); y++) {
for (register int x = 0; x < i.GetWidth(); x++) {
if (ar[y][x]) {
if (x1 == -1) {
x1 = x2 = x;
y1 = y2 = y;
} else if (sqrt(pow(x - x2, 2.0) + pow(y - y2, 2.0)) <= d) {
x2 = x;
y2 = y;
ar[y][x] = 1;
} else {
ar[y][x] = 0;
}
}
}
}
for (register int y = 0; y < i.GetHeight(); y++) {
for (register int x = 0; x < i.GetWidth(); x++) {
if (ar[y][x]) {
cdc.SetPixel(x, y, RGB(255, 255, 0));
}
}
}
register float radius = sqrt(pow(x1 - x2, 2.0) + pow(y1 - y2, 2.0));
float t = atan((float)(y2 - y1) / (x2 - x1)) * 180 / pi;
cdc.SelectObject(&p1);
cdc.MoveTo((x1 + x2) / 2 - radius / 2, (y1 + y2) / 2);
cdc.LineTo((x1 + x2) / 2 + radius / 2, (y1 + y2) / 2);
cdc.MoveTo((x1 + x2) / 2, (y1 + y2) / 2 - radius / 2);
cdc.LineTo((x1 + x2) / 2, (y1 + y2) / 2 + radius / 2);
CClientDC dc(this);
if (t >= -180 && t <= 180) {
char a[10] = "";
itoa(t, a, 10);
CString s;
s = a;
dc.TextOut(0, 300, s + _T("degree"));
}
i1.ReleaseDC();
cdc.Detach();
i1.BitBlt(dc.m_hDC, i.GetWidth() + 10, 0, SRCCOPY);
i1.Destroy();
}