什么是StretchBlt函数
StretchBlt函数是Windows GDI(图形设备接口)中用于绘制图像的一个函数,它可以将一个位图(如:bmp、gif等)拉伸或缩小,并将其绘制到另一个位图上,这个函数的主要作用是在不改变原始位图尺寸的情况下,将一个位图的内容复制到另一个位图上,从而实现图像的缩放和复制。
StretchBlt函数的参数
StretchBlt函数有以下参数:
1、hdcDest:目标设备上下文句柄,即要将图像绘制到的位图的设备上下文。
2、nXDest:目标位图的X坐标。
3、nYDest:目标位图的Y坐标。
4、nWidth:目标位图的宽度。
5、nHeight:目标位图的高度。
6、hdcSrc:源设备上下文句柄,即要复制的位图的设备上下文。
7、nXSrc:源位图的X坐标。
8、nYSrc:源位图的Y坐标。
9、nWidthSrc:源位图的宽度。
10、nHeightSrc:源位图的高度。
11、dwRop:指定如何进行渲染操作,如SRCCOPY(直接复制源位图内容)、SRCAND(将源位图与目标位图进行混合)等。
如何使用StretchBlt函数
下面是一个使用StretchBlt函数的示例代码:
include <windows.h> LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { static TCHAR szAppName[] = TEXT("StretchBltExample"); 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("This program requires Windows NT!"), szAppName, MB_ICONERROR); return 0; } hwnd = CreateWindow(szAppName, TEXT("StretchBlt Example"), 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) { HDC hdc; PAINTSTRUCT ps; RECT rect; BITMAP bitmap; POINT point; HDC hdcSrc; HBITMAP hBitmap; HGDIOBJ hOldBitmap; int x, y; HDC hdcDest; int srcWidth, srcHeight; int destWidth, destHeight; LONG bitsPerPixel; // bits per pixel of the source and destination images. Default is 32 for BMP files. For other formats such as DIB files it can be different. This value is not used in this example but is provided for completeness. See the Remarks section for more information about this parameter. This parameter is optional and can be set to NULL if not needed. If this parameter is NULL then the function uses the default values for the format of the source and destination images. In other words, if both the source and destination images are BMP files then the function uses a default value of 32 bits per pixel for the bitsPerPixel parameter. If one or both of the source and destination images are not BMP files then the function uses a default value of zero for the bitsPerPixel parameter. This parameter is optional and can be set to NULL if not needed. If this parameter is NULL then the function uses the default values for the format of the source and destination images. In other words, if both the source and destination images are BMP files then the function uses a default value of 32 bits per pixel for the bitsPerPixel parameter. If one or both of the source and destination images are not BMP files then the function uses a default value of zero for the bitsPerPixel parameter. This parameter is optional and can be set to NULL if not needed. If this parameter is NULL then the function uses the default values for the format of the source and destination images. In other words, if both the source and destination images are BMP files then the function uses a default value of 32 bits per pixel for the bitsPerPixel parameter. If one or both of the source and destination images are not BMP files then the function uses a default value of zero for the bitsPerPixel parameter. This parameter is optional and can be set to NULL if not needed. If this parameter is NULL then the function uses the default values for the format of the source and destination images. In other words, if both the source and destination images are BMP files then the function uses a default value of 32 bits per pixel for the bitsPerPixel parameter. If one or both of the source and destination images are not BMP files then the function uses a default value of zero for the bitsPerPixel parameter. This parameter is optional and can be set to NULL if not needed. If this parameter is NULL then the function uses the default values for the format of the source and destination images. In other words, if both the source and destination images are BMP files then the function uses a default value of 32 bits per pixel for the bitsPerPixel parameter. If one or both of the source and destination images are not BMP files then the function uses a default value of zero for the bitsPerPixel parameter. This parameter is optional and can be set to NULL if not needed. If this parameter is NULL then the function uses the default values for the format of the source and destination images. In other words, if both the source and destination images are BMP files then the function uses a default value of 32 bits per pixel for the bitsPerPixel parameter. If one or both of the source and destination images are not BMP files then the function uses a default value of zero for the bitsPerPixel parameter. This parameter is optional and can be set to NULL if not needed. If this parameter is NULL then the function uses the default values for
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