Bezier 样条曲线使用四个点来定义:两个端点(起点和终点)和两个控点(用于使其不同程度地弯曲)。
使用 PolyBezier 函数和 PolyBezierTo 函数可以绘制 Bezier 样条曲线:
BOOL PolyBezier(
HDC hdc, // 设备环境句柄
CONST POINT* lppt, // 端点和控制点(顺序是开始点、第一控点、第二控点、终点)
DWORD cPoints // 端点和控点的总数量
);
BOOL PolyBezierTo(
HDC hdc, // 设备环境句柄
CONST POINT *lppt, // 端点和控制点(顺序是第一控点、第二控点、终点)
DWORD cCount // 端点和控点的总数量
);
注:PolyBezierTo 函数把当前位置当做开始点,所以只需要给定其他三个点,函数返回时,当前位置将被设置为终点。
#include <windows.h>
void DrawBezier(HDC hdc, POINT apt[]) {
PolyBezier(hdc, apt, 4);
MoveToEx(hdc, apt[0].x, apt[0].y, NULL);
LineTo(hdc, apt[1].x, apt[1].y);
MoveToEx(hdc, apt[2].x, apt[2].y, NULL);
LineTo(hdc, apt[3].x, apt[3].y);
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
HDC hdc;
PAINTSTRUCT ps;
static int cxClient, cyClient;
static POINT apt[4];
switch (message) {
case WM_SIZE:
cxClient = LOWORD(lParam);
cyClient = HIWORD(lParam);
apt[0].x = cxClient / 4;
apt[0].y = cyClient / 2;
apt[1].x = cxClient * 4 / 8;
apt[1].y = cyClient / 4;
apt[2].x = cxClient * 4 / 8;
apt[2].y = cyClient * 3 / 4;
apt[3].x = cxClient * 3 / 4;
apt[3].y = cyClient / 2;
return 0;
case WM_LBUTTONDOWN:
case WM_RBUTTONDOWN:
case WM_MOUSEMOVE:
if (wParam & MK_LBUTTON || wParam & MK_RBUTTON) {
hdc = GetDC(hwnd);
SelectObject(hdc, GetStockObject(BLACK_PEN));
DrawBezier(hdc, apt);
if (wParam & MK_LBUTTON) {
apt[1].x = LOWORD(lParam);
apt[1].y = HIWORD(lParam);
}
if (wParam & MK_RBUTTON) {
apt[2].x = LOWORD(lParam);
apt[2].y = HIWORD(lParam);
}
SelectObject(hdc, GetStockObject(WHITE_PEN));
DrawBezier(hdc, apt);
ReleaseDC(hwnd, hdc);
}
return 0;
case WM_PAINT:
InvalidateRect(hwnd, NULL, TRUE);
hdc = BeginPaint(hwnd, &ps);
SelectObject(hdc, GetStockObject(WHITE_PEN));
DrawBezier(hdc, apt);
EndPaint(hwnd, &ps);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
LPCTSTR lpszClassName = TEXT("BezierDemo");
LPCTSTR lpszWindowName = TEXT("Bezier Demo");
WNDCLASS wndclass;
HWND hwnd;
MSG msg;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hInstance = hInstance;
wndclass.lpfnWndProc = WndProc;
wndclass.lpszClassName = lpszClassName;
wndclass.lpszMenuName = lpszWindowName;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
if (!RegisterClass(&wndclass)) {
MessageBox(NULL, TEXT("This program requires Windows NT!"), lpszWindowName, MB_ICONERROR);
return 0;
}
hwnd = CreateWindow(
lpszClassName,
lpszWindowName,
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
NULL,
NULL,
hInstance,
NULL
);
ShowWindow(hwnd, nCmdShow);
UpdateWindow(hwnd);
while (GetMessage(&msg, NULL, 0, 0)) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
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🔗 原文链接:https://alone.cafe/2018/06/gdibezieryang-tiao-qu-xian
📅 最后更新:2018年06月01日 Friday 06:30
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