C语言漫谈（二） 图像显示 Windows和Linux

　　关于图像显示有很多库可以用，Windows下有GDI，GDI+，D3D等，Linux下有X Window和Wayland，此外还有OpenGL ，SDL等图形库以及各种GUI库。

　　了解最原始的方式，对于加深理解依然是有帮助的。下面给Windows和Linux下显示位图的最简单例子：

1.Windows用GDI显示图像的例子：

 /*
 * FileName: Image_Win.c
 * Usage:    tcc -luser32 -lgdi32 -run Image_Win.c
 */

 #include <windows.h>
 #include <stdlib.h>
 //
 typedef unsigned char byte;

 typedef struct {
     int Width;
     int Height;
     byte *Data;
 } Image;

 LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM w, LPARAM l)
 {
     HDC hdc;
     RECT rect;
     Image img;
     BITMAPINFO bmi;
     PAINTSTRUCT ps;
     int iRowLength;
     //
     ZeroMemory(&bmi, sizeof(BITMAPINFO));
     bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
     bmi.bmiHeader.biPlanes = ;
     bmi.bmiHeader.biBitCount = ;
     bmi.bmiHeader.biCompression = BI_RGB;
     //
     switch (msg) {
     case WM_DESTROY:
         PostQuitMessage();
         break;
     case WM_PAINT:
         hdc = BeginPaint (hwnd, &ps) ;
         GetClientRect(hwnd,&rect);
         img.Width = rect.right - rect.left;
         iRowLength = ((img.Width* *  + ) & ~) >> ;
         img.Height = rect.bottom - rect.top;
         img.Data =  (byte*)malloc(iRowLength*img.Height);
         for(int i=;i<iRowLength*img.Height;i++)
             img.Data[i] = rand()%;
         bmi.bmiHeader.biWidth = img.Width;
         bmi.bmiHeader.biHeight = img.Height;
         SetDIBitsToDevice(hdc, , , img.Width, img.Height,
                           , , , img.Height, img.Data, &bmi, DIB_RGB_COLORS);
         break;
     default:
         return DefWindowProc(hwnd, msg, w, l);
     }
     return ;
 }

 int main(int argc, char* argv[])
 {
     static TCHAR szAppName[] = TEXT("RandColor");
     HWND         hwnd;
     MSG          msg;
     WNDCLASS     wndclass;
     int iCmdShow = ;
     HINSTANCE hInstance = NULL;
     //
     wndclass.style = CS_HREDRAW | CS_VREDRAW;
     wndclass.lpfnWndProc = WndProc;
     wndclass.cbClsExtra = ;
     wndclass.cbWndExtra = ;
     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 ;
     }
     hwnd = CreateWindow(szAppName, TEXT("Image"), WS_OVERLAPPEDWINDOW^WS_THICKFRAME,
                         CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
                         NULL, NULL, hInstance, NULL);
     //The message loop.
     ShowWindow(hwnd, iCmdShow);
     UpdateWindow(hwnd);

     while (GetMessage(&msg, NULL, , )) {
         TranslateMessage(&msg);
         DispatchMessage(&msg);
     }
     return ;
 }

　　

2.Linux下用X Window显示图像的例子：

 /*
 * FileName: Image_Linux.c
 * Usage:    tcc -lX11 -run Image_Linux.c
 */
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>

 #include <stdlib.h>

 #define WIDTH 640
 #define HEIGHT 480

 int main(int argc, char **argv)
 {
     int win_b_color;
     int win_w_color;
     XEvent xev;
     Window window;
     Visual *visual;
     XImage *ximage;
     GC gc;

     char*buffer=(char*)malloc(WIDTH*HEIGHT**sizeof(char));

     Display *display = XOpenDisplay(NULL);
     win_b_color = BlackPixel(display, DefaultScreen(display));
     win_w_color = BlackPixel(display, DefaultScreen(display));
     window = XCreateSimpleWindow(display,DefaultRootWindow(display),, , WIDTH, HEIGHT, ,win_b_color, win_w_color);
     visual = DefaultVisual(display, );
     //XSelectInput(display, window, ExposureMask | KeyPressMask);
     XMapWindow(display, window);
     XFlush(display);
     gc = XCreateGC(display, window, , NULL);
     //XEvent event;
     while () {
         for (int i = ; i < WIDTH*HEIGHT*; i ++)
             buffer[i] = rand()%;
         ximage=XCreateImage(display, visual, ,ZPixmap, , buffer,WIDTH, HEIGHT, , );
         XPutImage(display, window,gc, ximage, , , , ,WIDTH, HEIGHT);
     }
     return ;
 }

　　下一次将介绍矢量图方面的知识，主要以EMF,SVG和PostScript进行说明。