Win32 绘图基础 -- 绘制直线、边框、贝塞尔曲线、填充、裁剪
注：以下内容为学习笔记，多数是从书本、资料中得来，只为加深印象，及日后参考。然而本人表达能力较差，写的不好。因非翻译、非转载，只好选原创，但多数乃摘抄，实为惭愧。但若能帮助一二访客，幸甚！
2）在处理非WM_PAINT消息时由Windows程序获取：
4）更通用的获取设备环境句柄的函数：
5）处理位图时，有时可能会用到一个”内存设备环境“：
2）直线
绘图示例：
1.GDI
GDI 的一个主要目的就是支持与设备无关的图形。GDI提供了一种特殊的机制来彻底隔离应用程序和不同输出设备的特性，这样就可以支持与设备无关的图形。
2.设备环境
如果希望在图形输出设备上绘图，必须首先获取设备环境（即DC）的句柄。当Windows把这个句柄交给你的程序，Windows同时也就给予了你使用这个设备的权限。接着，在GDI函数中将这个句柄作为一个参数，告诉Windows在哪个设备上进行绘图。
设备环境中包含许多GDI函数如何工作的属性。
获取设备环境句柄：
1）在处理WM_PAINT消息时使用BeginPaint函数和EndPaint函数：
HDC hdc;
hdc = BeginPaint(hwnd, &ps);
// ...
EndPaint(hwnd, &ps);2）在处理非WM_PAINT消息时由Windows程序获取：
HDC hdc;
hdc = GetDC(hwnd);
//....
ReleaseDC(hwnd, hdc);3）获得用于整个窗口的，而不仅仅是窗口客户区的设备环境句柄：
hdc = GetWindowDC(hwnd);
// ...
ReleaseDC(hwnd, hdc);4）更通用的获取设备环境句柄的函数：
hdc = CreateDC(pszDriver, pszDevice, pszOutput, pData);
// ...
DeleteDC(hdc);hdc = CreateDC(TEXT("DISPLAY"), NULL, NULL, NULL);5）处理位图时，有时可能会用到一个”内存设备环境“：
hdcMem = CreateCompatibleDC(hdc);
// ..
DeleteDC(hdcMem);可以把一个位图选入内存设备环境，并且调用GDI函数绘制这个位图
6）图元文件是以二进制形式编码的GDI函数调用的集合。它可以通过获取一个图元文件的设备环境来创建：
hdcMeta = CreateMetaFile(pszFilename);
// ...
hmf = CloseMetaFile(hdcMeta);3.设备的尺寸
”分辨率“：每度量单位（通常是英寸）中含有的像素数。
常用函数：
GetSystemMetrics、GetDeviceCaps.
4.色彩ABC
获取视频适配器板卡上的内存的组织形式：
1)色彩平面的数目：
iPlanes= GetDeviceCaps(hdc, PLANES);2)每个像素的颜色位数:
iBitsPixel = GetDeviceCaps(hdc, BITSPIXEL);5.点和线的绘制
1）点
SetPixel(hdc, x, y, crColor);
crColor = GetPixel(hdc, x, y);2）直线
MoveToEx(hdc, xBeg, yBeg, NULL);
LineTo(hdc, xEnd, yEnd);数组的点连成线：
Polyline(hdc, apt, 5);用Polyline实现绘制正玄曲线：
/*-------------------------------------------------------------------
SINEWAVE.cpp -- sine wave Using polyline
--------------------------------------------------------------------*/
#include
#include
#define NUM 1000
#define TWOPI (2*3.14159)
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT("SineWave");
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = hInstance;
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;
if (!RegisterClass(&wndclass))
{
MessageBox(NULL, TEXT("Program requires Windows NT!"), szAppName, MB_ICONERROR);
return 0;
}
hwnd = CreateWindow(szAppName, TEXT("Sine Wave Using Polyline"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL);
ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
static int cxClient, cyClient;
HDC hdc;
int i;
PAINTSTRUCT ps;
POINT apt[NUM];
switch (message)
{
case WM_SIZE:
cxClient = LOWORD(lParam);
cyClient = HIWORD(lParam);
return 0;
case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
MoveToEx(hdc, 0, cyClient/2, NULL);
LineTo(hdc, cxClient, cyClient/2);
for (i = 0; i < NUM; i++)
{
apt[i].x = i*cxClient/NUM;
apt[i].y = (int)(cyClient / 2 * (1-sin(TWOPI * i / NUM)));
}
Polyline(hdc, apt, NUM);
EndPaint(hwnd, &ps);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
} 6.几个绘图函数：
Rectangle(hdc, xLeft, yTop, xRight, yBottom);
Ellipse(hdc, xLeft, yTop, xRight, yBottom);
RoundRect(hdc, xLeft, yTop, xRight, yBottom, xCornerEllipse, yCornerEllipse);
Arc(hdc, xLeft, yTop, xRight, yBottom, xStart, yStart, xEnd, yEnd);
Chord(hdc, xLeft, yTop, xRight, yBottom, xStart, yStart, xEnd, yEnd);
Pie(hdc, xLeft, yTop, xRight, yBottom, xStart, yStart, xEnd, yEnd);绘图示例：
/*-------------------------------------------------------------------
lineDemo.cpp -- Line-Drawing Demonstration Program
--------------------------------------------------------------------*/
#include
#include
#define NUM 1000
#define TWOPI (2*3.14159)
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT("lineDemo");
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = hInstance;
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;
if (!RegisterClass(&wndclass))
{
MessageBox(NULL, TEXT("Program requires Windows NT!"), szAppName, MB_ICONERROR);
return 0;
}
hwnd = CreateWindow(szAppName, TEXT("Line Demonstration"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL);
ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
static int cxClient, cyClient;
HDC hdc;
PAINTSTRUCT ps;
switch (message)
{
case WM_SIZE:
cxClient = LOWORD(lParam);
cyClient = HIWORD(lParam);
return 0;
case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
Rectangle(hdc, cxClient/8, cyClient/8, 7*cxClient/8, 7*cyClient/8);
MoveToEx(hdc, 0, 0, NULL);
LineTo(hdc, cxClient, cyClient);
MoveToEx(hdc, 0, cyClient, NULL);
LineTo(hdc, cxClient, 0);
Ellipse(hdc, cxClient/8, cyClient/8, 7*cxClient/8, 7*cyClient/8);
RoundRect(hdc, cxClient/4, cyClient/4, 3*cxClient/4, 3*cyClient/4, cxClient/4, cyClient/4);
EndPaint(hwnd, &ps);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}
7.贝塞尔样条曲线：
/*-------------------------------------------------------------------
bezier.cpp -- Bezier Splines Demo
--------------------------------------------------------------------*/
#include
#include
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT("Bezier");
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = hInstance;
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;
if (!RegisterClass(&wndclass))
{
MessageBox(NULL, TEXT("Program requires Windows NT!"), szAppName, MB_ICONERROR);
return 0;
}
hwnd = CreateWindow(szAppName, TEXT("Bezier Splines Demo"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL);
ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
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)
{
static POINT apt[4];
int cxClient, cyClient;
HDC hdc;
PAINTSTRUCT ps;
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 / 2;
apt[1].y = cyClient / 4;
apt[2].x = cxClient / 2;
apt[2].y = 3 * cyClient / 4;
apt[3].x = 3 * cxClient / 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(WHITE_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(BLACK_PEN));
DrawBezier(hdc, apt);
ReleaseDC(hwnd, hdc);
}
case WM_PAINT:
InvalidateRect(hwnd, NULL, TRUE);
hdc = BeginPaint(hwnd, &ps);
DrawBezier(hdc, apt);
EndPaint(hwnd, &ps);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}
8.填充区域
PeekMessage
在Windows中有很多”空闲时间“，在这期间所有的消息队列都是空的，Windows就在等待键盘或者鼠标的输入。那么能否在空闲期间从某种程度上获取控制，而一旦有消息加载到程序的消息队列，就释放控制呢？这就是PeekMessage的”用武之地“。
PeekMessage的意思，它是”偷看“而不是”获得“。它允许一个程序检查程序队列中的下一个消息，而不是真实地获得并删除它看到的消息。
GetMessage并不把控制权交还给程序，除非它从程序的消息队列中获得了消息。但PeekMessage却总是立即返回，不管消息是否出现。
随机矩形代码：
/*-------------------------------------------------------------------
randRect.cpp -- Displays Random Rectangles
--------------------------------------------------------------------*/
#include
#include
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
void DrawRectangle(HWND);
int cxClient, cyClient;
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT("RandRect");
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = hInstance;
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;
if (!RegisterClass(&wndclass))
{
MessageBox(NULL, TEXT("Program requires Windows NT!"), szAppName, MB_ICONERROR);
return 0;
}
hwnd = CreateWindow(szAppName, TEXT("Rand Rectangle"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL);
ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);
while (TRUE)
{
if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
if (msg.message == WM_QUIT)
break;
TranslateMessage(&msg);
DispatchMessage(&msg);
}
else
{
Sleep(100);
DrawRectangle(hwnd);
}
}
return msg.wParam;
}
void DrawRectangle(HWND hwnd)
{
HBRUSH hBrush;
HDC hdc;
RECT rect;
if (cxClient == 0 || cyClient == 0)
return;
SetRect(&rect, rand() % cxClient, rand() % cyClient, rand() % cxClient, rand() % cyClient);
hBrush = CreateSolidBrush(RGB(rand() % 256, rand() % 256, rand() % 256));
hdc = GetDC(hwnd);
FillRect(hdc, &rect, hBrush);
ReleaseDC(hwnd, hdc);
DeleteObject(hBrush);
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_SIZE:
cxClient = LOWORD(lParam);
cyClient = HIWORD(lParam);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}
9.矩形与区域的裁剪
InvalidRect函数使显示的矩形区域无效，并产生一个WM_PAINT消息。可以用来擦除客户区的内容，并产生一个WM_PAINT消息。
若处理区域而不是矩形可用：
InvalidateRgn(hwnd, hRgn, bErase);
ValidateRgn(hwnd, hRgn);
CLOVER程序：
由四个椭圆形成一个区域，然后把这个区域选入设备环境，接着从窗口的客户区中心发散绘制一系列直线。这些直线仅出现裁剪区内。
/*-------------------------------------------------------------------
clover.cpp -- Clover Drawing Program Using Regions
--------------------------------------------------------------------*/
#include
#include
#define TWO_PI (2.0 * 3.14159)
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
void DrawRectangle(HWND);
int cxClient, cyClient;
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT("clover");
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = hInstance;
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;
if (!RegisterClass(&wndclass))
{
MessageBox(NULL, TEXT("Program requires Windows NT!"), szAppName, MB_ICONERROR);
return 0;
}
hwnd = CreateWindow(szAppName, TEXT("Draw a Clover"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL);
ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
static HRGN hRgnClip;
static int cxClient, cyClient;
double fAngle, fRadius;
HCURSOR hCursor;
HDC hdc;
HRGN hRgnTemp[6];
int i;
PAINTSTRUCT ps;
switch (message)
{
case WM_SIZE:
cxClient = LOWORD(lParam);
cyClient = HIWORD(lParam);
hCursor = SetCursor(LoadCursor(NULL, IDC_WAIT));
ShowCursor(TRUE);
if (hRgnClip)
DeleteObject(hRgnClip);
hRgnTemp[0] = CreateEllipticRgn(0, cyClient/3, cxClient/2, 2*cyClient/3);
hRgnTemp[1] = CreateEllipticRgn(cxClient/2, cyClient/3, cxClient, 2*cyClient/3);
hRgnTemp[2] = CreateEllipticRgn(cxClient/3, 0, 2*cxClient/3, cyClient/2);
hRgnTemp[3] = CreateEllipticRgn(cxClient/3, cyClient/2, 2*cxClient/3, cyClient);
hRgnTemp[4] = CreateRectRgn(0, 0, 1, 1);
hRgnTemp[5] = CreateRectRgn(0, 0, 1, 1);
hRgnClip = CreateRectRgn(0, 0, 1, 1);
CombineRgn(hRgnTemp[4], hRgnTemp[0], hRgnTemp[1], RGN_OR);
CombineRgn(hRgnTemp[5], hRgnTemp[2], hRgnTemp[3], RGN_OR);
CombineRgn(hRgnClip, hRgnTemp[4], hRgnTemp[5], RGN_XOR);
for (i = 0; i < 6; i++)
DeleteObject(hRgnTemp[i]);
SetCursor(hCursor);
ShowCursor(FALSE);
return 0;
case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
SetViewportOrgEx(hdc, cxClient/2, cyClient/2, NULL);
SelectClipRgn(hdc, hRgnClip);
// hypot 计算直角三角形斜边的长
fRadius = _hypot(cxClient/2.0, cyClient/2.0);
for (fAngle = 0.0; fAngle < TWO_PI; fAngle += TWO_PI/360)
{
MoveToEx(hdc, 0, 0, NULL);
LineTo(hdc, int(fRadius * cos(fAngle) + 0.5), int(-fRadius * sin(fAngle) + 0.5));
}
EndPaint(hwnd, &ps);
return 0;
case WM_DESTROY:
DeleteObject(hRgnClip);
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}