| /* |
| * glRead/DrawPixels test |
| */ |
| |
| |
| #include <GL/glew.h> |
| #include <stdio.h> |
| #include <string.h> |
| #include <stdlib.h> |
| #include <GL/glut.h> |
| |
| static int Width = 250, Height = 250; |
| static GLfloat Zoom = 1.0; |
| |
| static void Init(void) |
| { |
| fprintf(stderr, "GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER)); |
| fprintf(stderr, "GL_VERSION = %s\n", (char *) glGetString(GL_VERSION)); |
| fprintf(stderr, "GL_VENDOR = %s\n", (char *) glGetString(GL_VENDOR)); |
| fflush(stderr); |
| glClearColor(0.3, 0.1, 0.3, 0.0); |
| } |
| |
| static void Reshape(int width, int height) |
| { |
| Width = width / 2; |
| Height = height; |
| /* draw on left half (we'll read that area) */ |
| glViewport(0, 0, Width, height); |
| glMatrixMode(GL_PROJECTION); |
| glLoadIdentity(); |
| glOrtho(-1.0, 1.0, -1.0, 1.0, -0.5, 1000.0); |
| glMatrixMode(GL_MODELVIEW); |
| } |
| |
| static void Key(unsigned char key, int x, int y) |
| { |
| switch (key) { |
| case 27: |
| exit(0); |
| default: |
| return; |
| } |
| glutPostRedisplay(); |
| } |
| |
| static void Draw(void) |
| { |
| GLfloat *image = (GLfloat *) malloc(Width * Height * 4 * sizeof(GLfloat)); |
| |
| glClear(GL_COLOR_BUFFER_BIT); |
| |
| glBegin(GL_TRIANGLES); |
| glColor3f(.8,0,0); |
| glVertex3f(-0.9, -0.9, -30.0); |
| glColor3f(0,.9,0); |
| glVertex3f( 0.9, -0.9, -30.0); |
| glColor3f(0,0,.7); |
| glVertex3f( 0.0, 0.9, -30.0); |
| glEnd(); |
| |
| glBegin(GL_QUADS); |
| glColor3f(1, 1, 1); |
| glVertex2f(-1.0, -1.0); |
| glVertex2f(-0.9, -1.0); |
| glVertex2f(-0.9, -0.9); |
| glVertex2f(-1.0, -0.9); |
| glEnd(); |
| |
| glReadPixels(0, 0, Width, Height, GL_RGBA, GL_FLOAT, image); |
| printf("Pixel(0,0) = %f, %f, %f, %f\n", |
| image[0], image[1], image[2], image[3]); |
| /* draw to right half of window */ |
| glWindowPos2iARB(Width, 0); |
| glPixelZoom(Zoom, Zoom); |
| glDrawPixels(Width, Height, GL_RGBA, GL_FLOAT, image); |
| free(image); |
| |
| glutSwapBuffers(); |
| } |
| |
| int main(int argc, char **argv) |
| { |
| glutInit(&argc, argv); |
| glutInitWindowPosition(0, 0); |
| glutInitWindowSize(Width*2, Height); |
| glutInitDisplayMode(GLUT_RGB | GLUT_ALPHA | GLUT_DOUBLE); |
| if (glutCreateWindow(argv[0]) == GL_FALSE) { |
| exit(1); |
| } |
| |
| if (argc > 1) |
| Zoom = atof(argv[1]); |
| |
| glewInit(); |
| |
| Init(); |
| |
| glutReshapeFunc(Reshape); |
| glutKeyboardFunc(Key); |
| glutDisplayFunc(Draw); |
| glutMainLoop(); |
| return 0; |
| } |