OpenGL: 图像像素操作

#define GLUT_DISABLE_ATEXIT_HACK
#include <Windows.h>
#include <stdio.h>
#include <gl/glut.h>
#include <gl/glaux.h>
#pragma comment(lib,"glaux.lib")
#pragma comment(lib, "glut32.lib")

AUX_RGBImageRec* Image;
GLint iWidth,iHeight,iMode=1;
GLubyte* pImage;

void MenuCreate(void)
{
	glutAddMenuEntry("正常显示", 1);
	glutAddMenuEntry("翻转图像", 2);
	glutAddMenuEntry("缩小图像", 3);
	glutAddMenuEntry("红色通道", 4);
	glutAddMenuEntry("绿色通道", 5);
	glutAddMenuEntry("蓝色通道", 6);
	glutAddMenuEntry(" 灰度图 ", 7);
	glutAddMenuEntry("反转颜色", 8);

	glutAttachMenu(GLUT_RIGHT_BUTTON);
}
void Initialization(void)
{
	glClearColor(0,0,0,1);

	MenuCreate();

	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
	Image = auxDIBImageLoad("11.bmp");
	iWidth  = Image->sizeX;
	iHeight = Image->sizeY;
	pImage  = Image->data;
}

void OnDisplay(void)
{
	glClear(GL_COLOR_BUFFER_BIT);

	GLbyte *pModified = NULL;
	GLfloat invert[256];
	GLint i;

	glRasterPos2i(0, 0);

	switch(iMode)
	{
	case 2:
		glPixelZoom(-1.0f, -1.0f);
		glRasterPos2i(iWidth - 1, iHeight - 1);
		break;

	case 3:
		glPixelZoom(0.5f, 0.5f);
		break;

	case 4:
		glPixelTransferf(GL_RED_SCALE, 1.0f);
		glPixelTransferf(GL_GREEN_SCALE, 0.0f);
		glPixelTransferf(GL_BLUE_SCALE, 0.0f);
		break;

	case 5:
		glPixelTransferf(GL_RED_SCALE, 0.0f);
		glPixelTransferf(GL_GREEN_SCALE, 1.0f);
		glPixelTransferf(GL_BLUE_SCALE, 0.0f);
		break;

	case 6:
		glPixelTransferf(GL_RED_SCALE, 0.0f);
		glPixelTransferf(GL_GREEN_SCALE, 0.0f);
		glPixelTransferf(GL_BLUE_SCALE, 1.0f);
		break;

	case 7:
		glDrawPixels(iWidth,iHeight, GL_RGB, GL_UNSIGNED_BYTE, pImage);
		pModified = (GLbyte*)new GLbyte[iWidth * iHeight];

		glPixelTransferf(GL_RED_SCALE, 0.3f);
		glPixelTransferf(GL_GREEN_SCALE, 0.59f);
		glPixelTransferf(GL_BLUE_BITS, 0.11f);

		glReadPixels(0, 0, iWidth, iHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, pModified);
		glPixelTransferf(GL_RED_SCALE, 1.0f);
		glPixelTransferf(GL_GREEN_SCALE, 1.0f);
		glPixelTransferf(GL_BLUE_SCALE, 1.0f);
		break;

	case 8:
		invert[0] = 1.0f;
		for(i = 1; i < 256; i++)
		{
			invert[i] = 1.0f - (1.0f / 255.0f * GLfloat(i));
		}
		glPixelMapfv(GL_PIXEL_MAP_R_TO_R, 255, invert);
		glPixelMapfv(GL_PIXEL_MAP_G_TO_G, 255, invert);
		glPixelMapfv(GL_PIXEL_MAP_B_TO_B, 255, invert);
		glPixelTransferf(GL_MAP_COLOR,GL_TRUE);
		break;

	case 1:
	default:
		break;
	}

	if(pModified == NULL)
	{
		glDrawPixels(iWidth, iHeight, GL_RGB,GL_UNSIGNED_BYTE, pImage);
	}
	else
	{
		glDrawPixels(iWidth, iHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, pModified);
		delete [] pModified;
	}

	glPixelTransferi(GL_MAP_COLOR, GL_FALSE);
	glPixelTransferf(GL_RED_SCALE, 1.0f);
	glPixelTransferf(GL_GREEN_SCALE, 1.0f);
	glPixelTransferf(GL_BLUE_SCALE, 1.0f);
	glPixelZoom(1.0f, 1.0f);

	glutSwapBuffers();
}

void OnReshape(int w,int h)
{
	GLfloat aspectRatio=(GLfloat)w / (GLfloat)h;//计算窗口的纵横比
	GLfloat winWidth,winHeight;

	glViewport(0, 0, w, h);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	if(w <= h)
	{                               //根据纵横比计算绘图区域的宽和高
		winWidth = 400;
		winHeight = 400 * aspectRatio;
	}
	else
	{
		winWidth = 400 * aspectRatio;
		winHeight= 400;
	}
	gluOrtho2D(0, winWidth, 0, winHeight);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

void OnMenu(int value)
{
	iMode = value;

	glutPostRedisplay();
}

void main(int argc,char* argv[])
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowSize(400, 400);
	glutCreateWindow("EXAM703");

	glutCreateMenu(OnMenu);
	glutDisplayFunc(OnDisplay);
	glutReshapeFunc(OnReshape);

	Initialization();
	glutMainLoop();
}