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