/** * glCopyPixels test * * Brian Paul * 14 Sep 2007 */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <GL/glew.h> #include <GL/glut.h> #include "readtex.h" #define IMAGE_FILE "../images/arch.rgb" static int ImgWidth, ImgHeight; static GLenum ImgFormat; static GLubyte *Image = NULL; static int WinWidth = 800, WinHeight = 800; static int Xpos, Ypos; static int Scissor = 0; static float Xzoom, Yzoom; static GLboolean DrawFront = GL_FALSE; static GLboolean Dither = GL_TRUE; static void Reset( void ) { Xpos = Ypos = 20; Scissor = 0; Xzoom = Yzoom = 1.0; } static void Display( void ) { const int dx = (WinWidth - ImgWidth) / 2; const int dy = (WinHeight - ImgHeight) / 2; if (DrawFront) { glDrawBuffer(GL_FRONT); glReadBuffer(GL_FRONT); } else { glDrawBuffer(GL_BACK); glReadBuffer(GL_BACK); } glClear( GL_COLOR_BUFFER_BIT ); /* draw original image */ glWindowPos2iARB(dx, dy); glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, Image); if (Scissor) glEnable(GL_SCISSOR_TEST); /* draw copy */ glPixelZoom(Xzoom, Yzoom); glWindowPos2iARB(Xpos, Ypos); glCopyPixels(dx, dy, ImgWidth, ImgHeight, GL_COLOR); glPixelZoom(1, 1); glDisable(GL_SCISSOR_TEST); if (DrawFront) glFinish(); else glutSwapBuffers(); } static void Reshape( int width, int height ) { WinWidth = width; WinHeight = height; glViewport( 0, 0, width, height ); glMatrixMode( GL_PROJECTION ); glLoadIdentity(); glOrtho( 0.0, width, 0.0, height, 0.0, 2.0 ); glMatrixMode( GL_MODELVIEW ); glLoadIdentity(); glScissor(width/4, height/4, width/2, height/2); } static void Key( unsigned char key, int x, int y ) { (void) x; (void) y; switch (key) { case ' ': Reset(); break; case 'd': Dither = !Dither; if (Dither) glEnable(GL_DITHER); else glDisable(GL_DITHER); break; case 's': Scissor = !Scissor; break; case 'x': Xzoom -= 0.1; break; case 'X': Xzoom += 0.1; break; case 'y': Yzoom -= 0.1; break; case 'Y': Yzoom += 0.1; break; case 'f': DrawFront = !DrawFront; printf("glDrawBuffer(%s)\n", DrawFront ? "GL_FRONT" : "GL_BACK"); break; case 27: exit(0); break; } glutPostRedisplay(); } static void SpecialKey( int key, int x, int y ) { const int step = (glutGetModifiers() & GLUT_ACTIVE_SHIFT) ? 10 : 1; (void) x; (void) y; switch (key) { case GLUT_KEY_UP: Ypos += step; break; case GLUT_KEY_DOWN: Ypos -= step; break; case GLUT_KEY_LEFT: Xpos -= step; break; case GLUT_KEY_RIGHT: Xpos += step; break; } glutPostRedisplay(); } static void Init( GLboolean ciMode, const char *filename ) { printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION)); printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER)); Image = LoadRGBImage( filename, &ImgWidth, &ImgHeight, &ImgFormat ); if (!Image) { printf("Couldn't read %s\n", filename); exit(0); } if (ciMode) { /* Convert RGB image to grayscale */ GLubyte *indexImage = (GLubyte *) malloc( ImgWidth * ImgHeight ); GLint i; for (i=0; i<ImgWidth*ImgHeight; i++) { int gray = Image[i*3] + Image[i*3+1] + Image[i*3+2]; indexImage[i] = gray / 3; } free(Image); Image = indexImage; ImgFormat = GL_COLOR_INDEX; for (i=0;i<255;i++) { float g = i / 255.0; glutSetColor(i, g, g, g); } } printf("Loaded %d by %d image\n", ImgWidth, ImgHeight ); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glPixelStorei(GL_UNPACK_ROW_LENGTH, ImgWidth); Reset(); } static void Usage(void) { printf("Keys:\n"); printf(" SPACE Reset Parameters\n"); printf(" Up/Down Move image up/down (SHIFT for large step)\n"); printf(" Left/Right Move image left/right (SHIFT for large step)\n"); printf(" x Decrease X-axis PixelZoom\n"); printf(" X Increase X-axis PixelZoom\n"); printf(" y Decrease Y-axis PixelZoom\n"); printf(" Y Increase Y-axis PixelZoom\n"); printf(" s Toggle GL_SCISSOR_TEST\n"); printf(" f Toggle front/back buffer drawing\n"); printf(" ESC Exit\n"); } int main( int argc, char *argv[] ) { GLboolean ciMode = GL_FALSE; const char *filename = IMAGE_FILE; int i = 1; if (argc > i && strcmp(argv[i], "-ci")==0) { ciMode = GL_TRUE; i++; } if (argc > i) { filename = argv[i]; } glutInit( &argc, argv ); glutInitWindowPosition( 0, 0 ); glutInitWindowSize( WinWidth, WinHeight ); if (ciMode) glutInitDisplayMode( GLUT_INDEX | GLUT_DOUBLE ); else glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE); glutCreateWindow(argv[0]); glewInit(); Init(ciMode, filename); Usage(); glutReshapeFunc( Reshape ); glutKeyboardFunc( Key ); glutSpecialFunc( SpecialKey ); glutDisplayFunc( Display ); glutMainLoop(); return 0; }