progs/demos/gamma.c

   1
   2 /* Draw test patterns to help determine correct gamma value for a display.
   3    When the intensities of the inner squares nearly match the intensities
   4    of their frames (from some distance the borders should disappear) then
   5    you've found the right gamma value.
   6
   7    You can set Mesa's gamma values (for red, green and blue) with the
   8    MESA_GAMMA environment variable.  But only on X windows!
   9    For example:
  10         setenv MESA_GAMMA 1.5 1.6 1.4
  11    Sets the red gamma value to 1.5, green to 1.6 and blue to 1.4.
  12    See the main README file for more information.
  13
  14    For more info about gamma correction see:
  15    http://www.inforamp.net/~poynton/notes/colour_and_gamma/GammaFAQ.html
  16
  17    This program is in the public domain
  18
  19    Brian Paul  19 Oct 1995
  20    Kai Schuetz 05 Jun 1999 */
  21
  22 /* Conversion to GLUT by Mark J. Kilgard */
  23
  24
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <stdlib.h>
  28 #include <GL/glut.h>
  29
  30 static void
  31 Reshape(int width, int height)
  32 {
  33   glViewport(0, 0, (GLint) width, (GLint) height);
  34
  35   glMatrixMode(GL_PROJECTION);
  36   glLoadIdentity();
  37   glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
  38   glMatrixMode(GL_MODELVIEW);
  39   glShadeModel(GL_FLAT);
  40 }
  41
  42 /* ARGSUSED1 */
  43 static void
  44 key_esc(unsigned char key, int x, int y)
  45 {
  46   if(key == 27) exit(0);  /* Exit on Escape */
  47 }
  48
  49 static GLubyte p25[] = {
  50   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  51   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  52   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  53   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  54   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  55   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  56   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  57   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  58   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  59   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  60   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  61   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  62   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  63   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  64   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  65   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  66 };
  67
  68 static GLubyte p50[] = {
  69   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  70   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  71   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  72   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  73   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  74   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  75   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  76   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  77   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  78   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  79   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  80   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  81   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  82   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  83   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  84   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  85 };
  86
  87 static GLubyte p75[] = {
  88   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  89   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  90   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  91   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  92   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  93   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  94   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  95   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  96   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  97   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  98   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
  99   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 100   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 101   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 102   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 103   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 104 };
 105
 106 static GLubyte *stippletab[4] = {NULL, p25, p50, p75};
 107
 108 static void
 109 gamma_ramp(GLfloat yoffs, GLfloat r, GLfloat g, GLfloat b)
 110 {
 111   GLint d;
 112
 113   glColor3f(0.0, 0.0, 0.0);     /* solid black, no stipple */
 114   glRectf(-1.0, yoffs, -0.6, yoffs + 0.5);
 115
 116   for(d = 1; d < 4; d++) {  /* increasing density from 25% to 75% */
 117     GLfloat xcoord = (-1.0 + d*0.4);
 118     GLfloat t = d * 0.25;
 119
 120     glColor3f(r*t, g*t, b*t); /* draw outer rect */
 121     glRectf(xcoord, yoffs, xcoord+0.4, yoffs + 0.5);
 122
 123     glColor3f(0.0, 0.0, 0.0);   /* "clear" inner rect */
 124     glRectf(xcoord + 0.1, yoffs + 0.125, xcoord + 0.3, yoffs + 0.375);
 125
 126     glColor3f(r, g, b);         /* draw stippled inner rect */
 127     glEnable(GL_POLYGON_STIPPLE);
 128     glPolygonStipple(stippletab[d]);
 129     glRectf(xcoord + 0.1, yoffs + 0.125, xcoord + 0.3, yoffs + 0.375);
 130     glDisable(GL_POLYGON_STIPPLE);
 131   }
 132   glColor3f(r, g, b);           /* solid color, no stipple */
 133   glRectf(0.6, yoffs, 1.0, yoffs + 0.5);
 134 }
 135
 136 static void
 137 display(void)
 138 {
 139   gamma_ramp( 0.5, 1.0, 1.0, 1.0); /* white ramp */
 140   gamma_ramp( 0.0, 1.0, 0.0, 0.0); /* red ramp */
 141   gamma_ramp(-0.5, 0.0, 1.0, 0.0); /* green ramp */
 142   gamma_ramp(-1.0, 0.0, 0.0, 1.0); /* blue ramp */
 143   glFlush();
 144 }
 145
 146 int
 147 main(int argc, char **argv)
 148 {
 149   glutInitWindowSize(500, 400);
 150   glutInit(&argc, argv);
 151   glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
 152   glutCreateWindow("gamma test patterns");
 153   glutReshapeFunc(Reshape);
 154   glutDisplayFunc(display);
 155   glutKeyboardFunc(key_esc);
 156
 157   glutMainLoop();
 158   return 0;             /* ANSI C requires main to return int. */
 159 }