main.cpp

一本关于OPenGL的很好的电子书

#define WIN32_LEAN_AND_MEAN		// trim the excess fat from Windows

/*******************************************************************
*	Program: Chapter 7 Bitmap Example 3
*	Author: Kevin Hawkins
*	Description: Loads and displays a .BMP file in the window. When
*			     the user presses the 'S' or 's' key, the window
*				 contents are saved to disk.
********************************************************************/

////// Defines
#define BITMAP_ID 0x4D42		// the universal bitmap ID

////// Includes
#include <windows.h>		// standard Windows app include
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <gl/gl.h>			// standard OpenGL include
#include <gl/glu.h>			// OpenGL utilties
#include <gl/glaux.h>		// OpenGL auxiliary functions

////// Global Variables
HDC g_HDC;				// global device context
bool fullScreen = false;		// true = fullscreen; false = windowed
bool keyPressed[256];		// holds true for keys that are pressed		

////// Bitmap Information
BITMAPINFOHEADER	bitmapInfoHeader;		// bitmap info header
unsigned char*		bitmapData;			// the bitmap data
void*               imageData;			// the screen image data

// DrawBitmap
// desc: draws the bitmap image data in bitmapImage at the location
//		 (200,200) in the window. (200,200) is the lower-left corner
//		 of the bitmap.
void DrawBitmap(long width, long height, unsigned char* bitmapImage)
{
	glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
	glRasterPos2i(200,200);
	glDrawPixels(width, height, GL_RGB, GL_UNSIGNED_BYTE, bitmapImage);
}



// LoadBitmapFile
// desc: Returns a pointer to the bitmap image of the bitmap specified
//       by filename. Also returns the bitmap header information.
//		 No support for 8-bit bitmaps.
unsigned char *LoadBitmapFile(char *filename, BITMAPINFOHEADER *bitmapInfoHeader)
{
	FILE *filePtr;								// the file pointer
	BITMAPFILEHEADER	bitmapFileHeader;		// bitmap file header
	unsigned char		*bitmapImage;			// bitmap image data
	int					imageIdx = 0;			// image index counter
	unsigned char		tempRGB;				// swap variable

	// open filename in "read binary" mode
	filePtr = fopen(filename, "rb");
	if (filePtr == NULL)
		return NULL;

	// read the bitmap file header
	fread(&bitmapFileHeader, sizeof(BITMAPFILEHEADER), 1, filePtr);
	
	// verify that this is a bitmap by checking for the universal bitmap id
	if (bitmapFileHeader.bfType != BITMAP_ID)
	{
		fclose(filePtr);
		return NULL;
	}

	// read the bitmap information header
	fread(bitmapInfoHeader, sizeof(BITMAPINFOHEADER), 1, filePtr);

	// move file pointer to beginning of bitmap data
	fseek(filePtr, bitmapFileHeader.bfOffBits, SEEK_SET);

	// allocate enough memory for the bitmap image data
	bitmapImage = (unsigned char*)malloc(bitmapInfoHeader->biSizeImage);

	// verify memory allocation
	if (!bitmapImage)
	{
		free(bitmapImage);
		fclose(filePtr);
		return NULL;
	}

	// read in the bitmap image data
	fread(bitmapImage, 1, bitmapInfoHeader->biSizeImage, filePtr);

	// make sure bitmap image data was read
	if (bitmapImage == NULL)
	{
		fclose(filePtr);
		return NULL;
	}

	// swap the R and B values to get RGB since the bitmap color format is in BGR
	for (imageIdx = 0; imageIdx < bitmapInfoHeader->biSizeImage; imageIdx+=3)
	{
		tempRGB = bitmapImage[imageIdx];
		bitmapImage[imageIdx] = bitmapImage[imageIdx + 2];
		bitmapImage[imageIdx + 2] = tempRGB;
	}

	// close the file and return the bitmap image data
	fclose(filePtr);
	return bitmapImage;
}

// WriteBitmapFile()
// desc: takes image data and saves it into a 24-bit RGB .BMP file
//       with width X height dimensions
int WriteBitmapFile(char *filename, int width, int height, unsigned char *imageData)
{
	FILE			 *filePtr;			// file pointer
	BITMAPFILEHEADER bitmapFileHeader;	// bitmap file header
	BITMAPINFOHEADER bitmapInfoHeader;	// bitmap info header
	int				 imageIdx;			// used for swapping RGB->BGR
	unsigned char	 tempRGB;			// used for swapping

	// open file for writing binary mode
	filePtr = fopen(filename, "wb");
	if (!filePtr)
		return 0;

	// define the bitmap file header
	bitmapFileHeader.bfSize = sizeof(BITMAPFILEHEADER);
	bitmapFileHeader.bfType = 0x4D42;
	bitmapFileHeader.bfReserved1 = 0;
	bitmapFileHeader.bfReserved2 = 0;
	bitmapFileHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
	
	// define the bitmap information header
	bitmapInfoHeader.biSize = sizeof(BITMAPINFOHEADER);
	bitmapInfoHeader.biPlanes = 1;
	bitmapInfoHeader.biBitCount = 24;						// 24-bit
	bitmapInfoHeader.biCompression = BI_RGB;				// no compression
	bitmapInfoHeader.biSizeImage = width * abs(height) * 3;	// width * height * (RGB bytes)
	bitmapInfoHeader.biXPelsPerMeter = 0;
	bitmapInfoHeader.biYPelsPerMeter = 0;
	bitmapInfoHeader.biClrUsed = 0;
	bitmapInfoHeader.biClrImportant = 0;
	bitmapInfoHeader.biWidth = width;						// bitmap width
	bitmapInfoHeader.biHeight = height;						// bitmap height

	// switch the image data from RGB to BGR
	for (imageIdx = 0; imageIdx < bitmapInfoHeader.biSizeImage; imageIdx+=3)
	{
		tempRGB = imageData[imageIdx];
		imageData[imageIdx] = imageData[imageIdx + 2];
		imageData[imageIdx + 2] = tempRGB;
	}

	// write the bitmap file header
	fwrite(&bitmapFileHeader, 1, sizeof(BITMAPFILEHEADER), filePtr);

	// write the bitmap info header
	fwrite(&bitmapInfoHeader, 1, sizeof(BITMAPINFOHEADER), filePtr);

	// write the image data
	fwrite(imageData, 1, bitmapInfoHeader.biSizeImage, filePtr);

	// close our file
	fclose(filePtr);

	return 1;
}


// Initialize
// desc: initializes OpenGL
void Initialize()
{
	// enable depth buffer, and backface culling
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_CULL_FACE);

	// Clear background to black
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

	// load our bitmap file
	bitmapData = LoadBitmapFile("test.bmp", &bitmapInfoHeader);
}

// Render
// desc: handles drawing of scene
void Render()
{
	// clear screen and depth buffer
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);												

	// draw the bitmap image
	DrawBitmap(bitmapInfoHeader.biWidth, bitmapInfoHeader.biHeight, bitmapData);

	glFlush();
	SwapBuffers(g_HDC);			// bring backbuffer to foreground
}

// SaveScreenshot()
// desc: takes a snapshot of the current window contents by retrieving
//       the screen data with glReadPixels() and writing the data to a file
void SaveScreenshot()
{
	imageData = malloc(800*600*3);		// allocate memory for the imageData
	memset(imageData, 0, 800*600*3);	// clear imageData memory contents

	// read the image data from the window
	glReadPixels(0, 0, 799, 599, GL_RGB, GL_UNSIGNED_BYTE, imageData);
	
	// write the image data to a file
	WriteBitmapFile("writeout.bmp", 800, 600, (unsigned char*)imageData);

	// free the image data memory
	free(imageData);
}

// function to set the pixel format for the device context
void SetupPixelFormat(HDC hDC)
{
	int nPixelFormat;					// our pixel format index

	static PIXELFORMATDESCRIPTOR pfd = {
		sizeof(PIXELFORMATDESCRIPTOR),	// size of structure
		1,								// default version
		PFD_DRAW_TO_WINDOW |			// window drawing support
		PFD_SUPPORT_OPENGL |			// OpenGL support
		PFD_DOUBLEBUFFER,				// double buffering support
		PFD_TYPE_RGBA,					// RGBA color mode
		32,								// 32 bit color mode
		0, 0, 0, 0, 0, 0,				// ignore color bits, non-palettized mode
		0,								// no alpha buffer
		0,								// ignore shift bit
		0,								// no accumulation buffer
		0, 0, 0, 0,						// ignore accumulation bits
		16,								// 16 bit z-buffer size
		0,								// no stencil buffer
		0,								// no auxiliary buffer
		PFD_MAIN_PLANE,					// main drawing plane
		0,								// reserved
		0, 0, 0 };						// layer masks ignored

	nPixelFormat = ChoosePixelFormat(hDC, &pfd);	// choose best matching pixel format

	SetPixelFormat(hDC, nPixelFormat, &pfd);		// set pixel format to device context
}

// the Windows Procedure event handler
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static HGLRC hRC;					// rendering context
	static HDC hDC;						// device context
	int width, height;					// window width and height

	switch(message)
	{
		case WM_CREATE:					// window is being created

			hDC = GetDC(hwnd);			// get current window's device context
			g_HDC = hDC;
			SetupPixelFormat(hDC);		// call our pixel format setup function

			// create rendering context and make it current
			hRC = wglCreateContext(hDC);
			wglMakeCurrent(hDC, hRC);

			return 0;
			break;

		case WM_CLOSE:					// windows is closing

			// deselect rendering context and delete it
			wglMakeCurrent(hDC, NULL);
			wglDeleteContext(hRC);

			// send WM_QUIT to message queue
			PostQuitMessage(0);

			return 0;
			break;

		case WM_SIZE:
			height = HIWORD(lParam);		// retrieve width and height
			width = LOWORD(lParam);

			if (height==0)					// don't want a divide by zero
			{
				height=1;					
			}

			glViewport(0, 0, width, height);	// reset the viewport to new dimensions
			glMatrixMode(GL_PROJECTION);		// set projection matrix current matrix
			glLoadIdentity();					// reset projection matrix

			// calculate aspect ratio of window
			//gluPerspective(54.0f,(GLfloat)width/(GLfloat)height,1.0f,1000.0f);
			glOrtho(0.0f, width - 1.0, 0.0, height - 1.0, -1.0, 1.0);

			glMatrixMode(GL_MODELVIEW);			// set modelview matrix
			glLoadIdentity();					// reset modelview matrix

			return 0;
			break;

		case WM_KEYDOWN:					// is a key pressed?
			keyPressed[wParam] = true;
			return 0;
			break;

		case WM_KEYUP:
			keyPressed[wParam] = false;
			return 0;
			break;

		default:
			break;
	}

	return (DefWindowProc(hwnd, message, wParam, lParam));
}

// the main windows entry point
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
	WNDCLASSEX windowClass;		// window class
	HWND	   hwnd;			// window handle
	MSG		   msg;				// message
	bool	   done;			// flag saying when our app is complete
	DWORD	   dwExStyle;		// Window Extended Style
	DWORD	   dwStyle;			// Window Style
	RECT	   windowRect;

	// temp var's
	int width = 800;
	int height = 600;
	int bits = 32;

	//fullScreen = TRUE;

	windowRect.left=(long)0;						// Set Left Value To 0
	windowRect.right=(long)width;					// Set Right Value To Requested Width
	windowRect.top=(long)0;							// Set Top Value To 0
	windowRect.bottom=(long)height;					// Set Bottom Value To Requested Height

	// fill out the window class structure
	windowClass.cbSize			= sizeof(WNDCLASSEX);
	windowClass.style			= CS_HREDRAW | CS_VREDRAW;
	windowClass.lpfnWndProc		= WndProc;
	windowClass.cbClsExtra		= 0;
	windowClass.cbWndExtra		= 0;
	windowClass.hInstance		= hInstance;
	windowClass.hIcon			= LoadIcon(NULL, IDI_APPLICATION);	// default icon
	windowClass.hCursor			= LoadCursor(NULL, IDC_ARROW);		// default arrow
	windowClass.hbrBackground	= NULL;								// don't need background
	windowClass.lpszMenuName	= NULL;								// no menu
	windowClass.lpszClassName	= "MyClass";
	windowClass.hIconSm			= LoadIcon(NULL, IDI_WINLOGO);		// windows logo small icon

	// register the windows class
	if (!RegisterClassEx(&windowClass))
		return 0;

	if (fullScreen)								// fullscreen?
	{
		DEVMODE dmScreenSettings;					// device mode
		memset(&dmScreenSettings,0,sizeof(dmScreenSettings));
		dmScreenSettings.dmSize = sizeof(dmScreenSettings);	
		dmScreenSettings.dmPelsWidth = width;		// screen width
		dmScreenSettings.dmPelsHeight = height;		// screen height
		dmScreenSettings.dmBitsPerPel = bits;		// bits per pixel
		dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;

		// 
		if (ChangeDisplaySettings(&dmScreenSettings, CDS_FULLSCREEN) != DISP_CHANGE_SUCCESSFUL)
		{
			// setting display mode failed, switch to windowed
			MessageBox(NULL, "Display mode failed", NULL, MB_OK);
			fullScreen=FALSE;	
		}
	}

	if (fullScreen)								// Are We Still In Fullscreen Mode?
	{
		dwExStyle=WS_EX_APPWINDOW;				// Window Extended Style
		dwStyle=WS_POPUP;						// Windows Style
		ShowCursor(FALSE);						// Hide Mouse Pointer
	}
	else
	{
		dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;	// Window Extended Style
		dwStyle=WS_OVERLAPPEDWINDOW;					// Windows Style
	}

	AdjustWindowRectEx(&windowRect, dwStyle, FALSE, dwExStyle);		// Adjust Window To True Requested Size

	// class registered, so now create our window
	hwnd = CreateWindowEx(NULL,									// extended style
						  "MyClass",							// class name
						  "Bitmap Example 3: Writing to a .BMP file",		// app name
						  dwStyle | WS_CLIPCHILDREN |
						  WS_CLIPSIBLINGS,
						  0, 0,									// x,y coordinate
						  windowRect.right - windowRect.left,
						  windowRect.bottom - windowRect.top,	// width, height
						  NULL,									// handle to parent
						  NULL,									// handle to menu
						  hInstance,							// application instance
						  NULL);								// no extra params

	// check if window creation failed (hwnd would equal NULL)
	if (!hwnd)
		return 0;

	ShowWindow(hwnd, SW_SHOW);			// display the window
	UpdateWindow(hwnd);					// update the window

	done = false;						// intialize the loop condition variable
	Initialize();						// initialize OpenGL

	// main message loop
	while (!done)
	{
		PeekMessage(&msg, hwnd, NULL, NULL, PM_REMOVE);

		if (msg.message == WM_QUIT)		// do we receive a WM_QUIT message?
		{
			done = true;				// if so, time to quit the application
		}
		else
		{
			if (keyPressed[VK_ESCAPE])
				done = true;
			else
			{
				if ((keyPressed['S']) || (keyPressed['s']))
					SaveScreenshot();
			
				Render();

				TranslateMessage(&msg);		// translate and dispatch to event queue
				DispatchMessage(&msg);
			}
		}
	}

	free(bitmapData);

	if (fullScreen)
	{
		ChangeDisplaySettings(NULL,0);		// If So Switch Back To The Desktop
		ShowCursor(TRUE);					// Show Mouse Pointer
	}

	return msg.wParam;
}