progs/demos/gamma.c

   1
   2 /* $Id: gamma.c,v 1.1 1999/08/19 00:55:40 jtg Exp $ */
   3
   4 /* Draw test patterns to help determine correct gamma value for a display.
   5    When the intensities of the inner squares nearly match the intensities
   6    of their frames (from some distance the borders should disappear) then
   7    you've found the right gamma value.
   8
   9    You can set Mesa's gamma values (for red, green and blue) with the
  10    MESA_GAMMA environment variable.  But only on X windows!
  11    For example:
  12         setenv MESA_GAMMA 1.5 1.6 1.4
  13    Sets the red gamma value to 1.5, green to 1.6 and blue to 1.4.
  14    See the main README file for more information.
  15
  16    For more info about gamma correction see:
  17    http://www.inforamp.net/~poynton/notes/colour_and_gamma/GammaFAQ.html
  18
  19    This program is in the public domain
  20
  21    Brian Paul  19 Oct 1995
  22    Kai Schuetz 05 Jun 1999 */
  23
  24 /* Conversion to GLUT by Mark J. Kilgard */
  25
  26 /*
  27  * $Log: gamma.c,v $
  28  * Revision 1.1  1999/08/19 00:55:40  jtg
  29  * Initial revision
  30  *
  31  * Revision 3.1  1999/06/19 01:35:38  brianp
  32  * merged in Kai Schuetz's RGB changes
  33  *
  34  * Revision 3.0  1998/02/14 18:42:29  brianp
  35  * initial rev
  36  *
  37  */
  38
  39
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include <stdlib.h>
  43 #include <GL/glut.h>
  44
  45 static void
  46 Reshape(int width, int height)
  47 {
  48   glViewport(0, 0, (GLint) width, (GLint) height);
  49
  50   glMatrixMode(GL_PROJECTION);
  51   glLoadIdentity();
  52   glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
  53   glMatrixMode(GL_MODELVIEW);
  54   glShadeModel(GL_FLAT);
  55 }
  56
  57 /* ARGSUSED1 */
  58 static void
  59 key_esc(unsigned char key, int x, int y)
  60 {
  61   if(key == 27) exit(0);  /* Exit on Escape */
  62 }
  63
  64 static GLubyte p25[] = {
  65   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  66   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  67   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  68   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  69   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  70   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  71   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  72   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  73   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  74   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  75   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  76   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  77   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  78   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  79   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  80   0xaa, 0xaa, 0xaa, 0xaa, 0x00, 0x00, 0x00, 0x00,
  81 };
  82
  83 static GLubyte p50[] = {
  84   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  85   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  86   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  87   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  88   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  89   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  90   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  91   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  92   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  93   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  94   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  95   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  96   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  97   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  98   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
  99   0xaa, 0xaa, 0xaa, 0xaa, 0x55, 0x55, 0x55, 0x55,
 100 };
 101
 102 static GLubyte p75[] = {
 103   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 104   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 105   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 106   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 107   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 108   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 109   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 110   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 111   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 112   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 113   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 114   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 115   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 116   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 117   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 118   0xaa, 0xaa, 0xaa, 0xaa, 0xff, 0xff, 0xff, 0xff,
 119 };
 120
 121 static GLubyte *stippletab[4] = {NULL, p25, p50, p75};
 122
 123 static void
 124 gamma_ramp(GLfloat yoffs, GLfloat r, GLfloat g, GLfloat b)
 125 {
 126   GLint d;
 127
 128   glColor3f(0.0, 0.0, 0.0);     /* solid black, no stipple */
 129   glRectf(-1.0, yoffs, -0.6, yoffs + 0.5);
 130
 131   for(d = 1; d < 4; d++) {  /* increasing density from 25% to 75% */
 132     GLfloat xcoord = (-1.0 + d*0.4);
 133
 134     glColor3f(r*d / 5.0, g*d / 5.0, b*d / 5.0); /* draw outer rect */
 135     glRectf(xcoord, yoffs, xcoord+0.4, yoffs + 0.5);
 136
 137     glColor3f(0.0, 0.0, 0.0);   /* "clear" inner rect */
 138     glRectf(xcoord + 0.1, yoffs + 0.125, xcoord + 0.3, yoffs + 0.375);
 139
 140     glColor3f(r, g, b);         /* draw stippled inner rect */
 141     glEnable(GL_POLYGON_STIPPLE);
 142     glPolygonStipple(stippletab[d]);
 143     glRectf(xcoord + 0.1, yoffs + 0.125, xcoord + 0.3, yoffs + 0.375);
 144     glDisable(GL_POLYGON_STIPPLE);
 145   }
 146   glColor3f(r, g, b);           /* solid color, no stipple */
 147   glRectf(0.6, yoffs, 1.0, yoffs + 0.5);
 148 }
 149
 150 static void
 151 display(void)
 152 {
 153   gamma_ramp( 0.5, 1.0, 1.0, 1.0); /* white ramp */
 154   gamma_ramp( 0.0, 1.0, 0.0, 0.0); /* red ramp */
 155   gamma_ramp(-0.5, 0.0, 1.0, 0.0); /* green ramp */
 156   gamma_ramp(-1.0, 0.0, 0.0, 1.0); /* blue ramp */
 157   glFlush();
 158 }
 159
 160 int
 161 main(int argc, char **argv)
 162 {
 163   glutInit(&argc, argv);
 164   glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
 165
 166   glutInitWindowPosition(50, 50);
 167   glutInitWindowSize(500, 400);
 168
 169   glutCreateWindow("gamma test patterns");
 170   glutReshapeFunc(Reshape);
 171   glutDisplayFunc(display);
 172   glutKeyboardFunc(key_esc);
 173
 174   glutMainLoop();
 175   return 0;             /* ANSI C requires main to return int. */
 176 }