Draw white square in lower-left corner to test orientation
diff --git a/progs/trivial/readpixels.c b/progs/trivial/readpixels.c
index b1f04f8..65fb81e 100644
--- a/progs/trivial/readpixels.c
+++ b/progs/trivial/readpixels.c
@@ -57,6 +57,14 @@
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]);