test glDraw/Read/CopyPixels()
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Brian Paul
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/* $Id: readpix.c,v 1.1 2000/03/01 16:23:14 brianp Exp $ */
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/*
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* glReadPixels and glCopyPixels test
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*
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* Brian Paul March 1, 2000 This file is in the public domain.
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*/
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/*
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* $Log: readpix.c,v $
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* Revision 1.1 2000/03/01 16:23:14 brianp
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* test glDraw/Read/CopyPixels()
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*
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*/
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <GL/glut.h>
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#include "../util/readtex.c" /* a hack, I know */
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#define IMAGE_FILE "../images/girl.rgb"
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static int ImgWidth, ImgHeight;
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static GLenum ImgFormat;
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static GLubyte *Image = NULL;
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static int APosX, APosY; /* simple drawpixels */
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static int BPosX, BPosY; /* read/draw pixels */
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static int CPosX, CPosY; /* copypixels */
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static GLboolean DrawFront = GL_FALSE;
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static GLboolean ScaleAndBias = GL_FALSE;
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static GLubyte *TempImage = NULL;
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static void
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Reset( void )
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{
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APosX = 5; APosY = 20;
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BPosX = APosX + ImgWidth + 5; BPosY = 20;
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CPosX = BPosX + ImgWidth + 5; CPosY = 20;
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}
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static void
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PrintString(const char *s)
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{
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while (*s) {
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glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
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s++;
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}
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}
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static void
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SetupPixelTransfer(GLboolean invert)
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{
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if (invert) {
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glPixelTransferf(GL_RED_SCALE, -1.0);
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glPixelTransferf(GL_RED_BIAS, 1.0);
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glPixelTransferf(GL_GREEN_SCALE, -1.0);
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glPixelTransferf(GL_GREEN_BIAS, 1.0);
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glPixelTransferf(GL_BLUE_SCALE, -1.0);
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glPixelTransferf(GL_BLUE_BIAS, 1.0);
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}
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else {
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glPixelTransferf(GL_RED_SCALE, 1.0);
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glPixelTransferf(GL_RED_BIAS, 0.0);
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glPixelTransferf(GL_GREEN_SCALE, 1.0);
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glPixelTransferf(GL_GREEN_BIAS, 0.0);
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glPixelTransferf(GL_BLUE_SCALE, 1.0);
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glPixelTransferf(GL_BLUE_BIAS, 0.0);
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}
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}
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static void
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Display( void )
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{
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glClear( GL_COLOR_BUFFER_BIT );
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glRasterPos2i(5, ImgHeight+25);
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PrintString("f = toggle front/back b = toggle scale/bias");
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/* draw original image */
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glRasterPos2i(APosX, 5);
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PrintString("Original");
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glRasterPos2i(APosX, APosY);
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glEnable(GL_DITHER);
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SetupPixelTransfer(GL_FALSE);
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glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, Image);
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/* do readpixels, drawpixels */
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glRasterPos2i(BPosX, 5);
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PrintString("Read/DrawPixels");
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SetupPixelTransfer(ScaleAndBias);
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glReadPixels(APosX, APosY, ImgWidth, ImgHeight,
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ImgFormat, GL_UNSIGNED_BYTE, TempImage);
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glRasterPos2i(BPosX, BPosY);
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glDisable(GL_DITHER);
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SetupPixelTransfer(GL_FALSE);
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glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, TempImage);
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/* do copypixels */
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glRasterPos2i(CPosX, 5);
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PrintString("CopyPixels");
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glRasterPos2i(CPosX, CPosY);
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glDisable(GL_DITHER);
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SetupPixelTransfer(ScaleAndBias);
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glCopyPixels(APosX, APosY, ImgWidth, ImgHeight, GL_COLOR);
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if (!DrawFront)
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glutSwapBuffers();
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}
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static void Reshape( int width, int height )
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{
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glViewport( 0, 0, width, height );
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glMatrixMode( GL_PROJECTION );
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glLoadIdentity();
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glOrtho( 0.0, width, 0.0, height, -1.0, 1.0 );
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glMatrixMode( GL_MODELVIEW );
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glLoadIdentity();
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}
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static void Key( unsigned char key, int x, int y )
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{
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(void) x;
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(void) y;
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switch (key) {
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case 'b':
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ScaleAndBias = !ScaleAndBias;
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break;
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case 'f':
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DrawFront = !DrawFront;
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if (DrawFront)
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glDrawBuffer(GL_FRONT);
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else
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glDrawBuffer(GL_BACK);
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printf("glDrawBuffer(%s)\n", DrawFront ? "GL_FRONT" : "GL_BACK");
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break;
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case 27:
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exit(0);
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break;
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}
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glutPostRedisplay();
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}
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static void SpecialKey( int key, int x, int y )
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{
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(void) x;
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(void) y;
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#if 0
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switch (key) {
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case GLUT_KEY_UP:
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Ypos += 1;
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break;
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case GLUT_KEY_DOWN:
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Ypos -= 1;
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break;
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case GLUT_KEY_LEFT:
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Xpos -= 1;
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break;
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case GLUT_KEY_RIGHT:
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Xpos += 1;
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break;
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}
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#endif
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glutPostRedisplay();
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}
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static void
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Init( GLboolean ciMode )
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{
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printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
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printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
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Image = LoadRGBImage( IMAGE_FILE, &ImgWidth, &ImgHeight, &ImgFormat );
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if (!Image) {
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printf("Couldn't read %s\n", IMAGE_FILE);
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exit(0);
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}
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if (ciMode) {
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/* Convert RGB image to grayscale */
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GLubyte *indexImage = malloc( ImgWidth * ImgHeight );
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GLint i;
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for (i=0; i<ImgWidth*ImgHeight; i++) {
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int gray = Image[i*3] + Image[i*3+1] + Image[i*3+2];
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indexImage[i] = gray / 3;
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}
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free(Image);
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Image = indexImage;
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ImgFormat = GL_COLOR_INDEX;
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for (i=0;i<255;i++) {
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float g = i / 255.0;
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glutSetColor(i, g, g, g);
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}
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}
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printf("Loaded %d by %d image\n", ImgWidth, ImgHeight );
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glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
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glPixelStorei(GL_UNPACK_ROW_LENGTH, ImgWidth);
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glPixelStorei(GL_PACK_ALIGNMENT, 1);
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glPixelStorei(GL_PACK_ROW_LENGTH, ImgWidth);
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Reset();
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TempImage = (GLubyte *) malloc(ImgWidth * ImgHeight * 4 * sizeof(GLubyte));
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assert(TempImage);
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}
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int main( int argc, char *argv[] )
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{
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GLboolean ciMode = GL_FALSE;
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if (argc > 1 && strcmp(argv[1], "-ci")==0) {
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ciMode = GL_TRUE;
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}
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glutInit( &argc, argv );
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glutInitWindowPosition( 0, 0 );
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glutInitWindowSize( 750, 250 );
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if (ciMode)
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glutInitDisplayMode( GLUT_INDEX | GLUT_DOUBLE );
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else
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glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
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glutCreateWindow(argv[0]);
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Init(ciMode);
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glutReshapeFunc( Reshape );
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glutKeyboardFunc( Key );
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glutSpecialFunc( SpecialKey );
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glutDisplayFunc( Display );
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glutMainLoop();
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return 0;
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}
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