glRead/DrawPixels test

progs/trivial/Makefile

@@ -46,6 +46,7 @@ SOURCES = \
 	quads.c \
 	quadstrip.c \
 	quadstrip-flat.c \
+	readpixels.c \
 	dlist-edgeflag.c \
 	dlist-dangling.c \
 	dlist-edgeflag-dangling.c \

progs/trivial/readpixels.c

@@ -0,0 +1,88 @@
+/*
+ * glRead/DrawPixels test
+ */
+
+
+#define GL_GLEXT_PROTOTYPES
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <GL/glut.h>
+
+static int Width = 250, Height = 250;
+
+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));
+   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();
+
+   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);
+   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);
+   }
+
+   Init();
+
+   glutReshapeFunc(Reshape);
+   glutKeyboardFunc(Key);
+   glutDisplayFunc(Draw);
+   glutMainLoop();
+   return 0;
+}