progs/demos/pixeltex.c

   1 /*
   2  * GL_SGIS_pixel_texture demo
   3  *
   4  * Brian Paul
   5  * 6 Apr 2000
   6  *
   7  * Copyright (C) 2000  Brian Paul   All Rights Reserved.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a
  10  * copy of this software and associated documentation files (the "Software"),
  11  * to deal in the Software without restriction, including without limitation
  12  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  13  * and/or sell copies of the Software, and to permit persons to whom the
  14  * Software is furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included
  17  * in all copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  20  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  22  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  23  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  24  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27
  28 /*
  29  * How this works:
  30  * 1. We load the image into a 2D texture.
  31  * 2. We generate a sequence of RGB images in which the R component
  32  *    is really the S texture coordinate and the G component is really
  33  *    the T texture coordinate.
  34  *    By warping the mapping from R to S and G to T we can get non-linear
  35  *    distortions.
  36  * 3. Draw the warped image (a 2-D warping function) with pixel texgen
  37  *    enabled.
  38  * 4. Loop over the warped images to animate.
  39  *
  40  * The pixel texgen extension can also be used to do color-space
  41  * conversions.  For example, we could convert YCR to RGB with a
  42  * 3D texture map which takes YCR as the S,T,R texture coordinate and
  43  * returns RGB texel values.
  44  *
  45  * You can use this extension in (at least) two ways:
  46  * 1. glDrawPixels w/ color space conversion/warping
  47  * 2. glDrawPixels to spatially warp another image in texture memory
  48  *
  49  * We're basically using glDrawPixels to draw a texture coordinate image.
  50  */
  51
  52
  53 #include <math.h>
  54 #include <stdio.h>
  55 #include <stdlib.h>
  56 #include <string.h>
  57 #include <GL/glut.h>
  58 #include <GL/glext.h>
  59 #include "readtex.c"   /* I know, this is a hack. */
  60
  61 #define TEXTURE_FILE "../images/girl.rgb"
  62
  63 static int ImgWidth = 300, ImgHeight = 300;
  64 #define FRAMES 20
  65 static GLubyte *ImgData[FRAMES];
  66 static GLint Frame = 0;
  67
  68 static GLboolean TextureFlag = GL_TRUE;
  69
  70
  71 static void Display( void )
  72 {
  73    glClear( GL_COLOR_BUFFER_BIT );
  74
  75    if (TextureFlag) {
  76       glEnable(GL_PIXEL_TEXTURE_SGIS);
  77       glEnable(GL_TEXTURE_2D);
  78    }
  79    else {
  80       glDisable(GL_PIXEL_TEXTURE_SGIS);
  81       glDisable(GL_TEXTURE_2D);
  82    }
  83
  84    glColor3f(1, 1, 1);
  85    glRasterPos2f(10, 10);
  86    glDrawPixels(ImgWidth, ImgHeight, GL_RGB, GL_UNSIGNED_BYTE, ImgData[Frame]);
  87
  88    glutSwapBuffers();
  89 }
  90
  91
  92 static void Reshape( int width, int height )
  93 {
  94    glViewport( 0, 0, width, height );
  95    glMatrixMode( GL_PROJECTION );
  96    glLoadIdentity();
  97    glOrtho(0, width, 0, height, -1, 1);
  98    glMatrixMode( GL_MODELVIEW );
  99    glLoadIdentity();
 100 }
 101
 102
 103 static void Key( unsigned char key, int x, int y )
 104 {
 105    (void) x;
 106    (void) y;
 107    switch (key) {
 108       case ' ':
 109          TextureFlag = !TextureFlag;
 110          break;
 111       case 27:
 112          exit(0);
 113          break;
 114    }
 115    glutPostRedisplay();
 116 }
 117
 118
 119 static void Idle(void)
 120 {
 121    Frame++;
 122    if (Frame >= FRAMES)
 123       Frame = 0;
 124    glutPostRedisplay();
 125 }
 126
 127
 128 static GLubyte warp(GLfloat s, int frame)
 129 {
 130    static const GLfloat pi = 3.14159265;
 131    static int halfFrame = FRAMES / 2;
 132    GLfloat y, weight, v;
 133    if (frame >= halfFrame)
 134       frame = halfFrame - (frame - halfFrame);
 135    y = sin(s * pi);
 136    weight = (float) frame / (FRAMES-1);
 137    v = y * (0.8 * weight + 0.2);
 138    return (GLint) (v * 255.0F);
 139 }
 140
 141
 142 static void InitImage(void)
 143 {
 144    int i, j, frame;
 145    for (frame = 0; frame < FRAMES; frame++) {
 146       ImgData[frame] = (GLubyte *) malloc(ImgWidth * ImgHeight * 3);
 147       for (i = 0; i < ImgHeight; i++) {
 148          for (j = 0; j < ImgWidth; j++) {
 149             GLubyte *pixel = ImgData[frame] + (i * ImgWidth + j) * 3;
 150             pixel[0] = warp((float) j / (ImgWidth - 0), frame);
 151             pixel[1] = warp((float) i / (ImgHeight - 0), frame);
 152             pixel[2] = 0.0;
 153          }
 154       }
 155    }
 156 }
 157
 158
 159 static void Init( int argc, char *argv[] )
 160 {
 161    const char *exten = (const char *) glGetString(GL_EXTENSIONS);
 162    if (!strstr(exten, "GL_SGIS_pixel_texture")) {
 163       printf("Sorry, GL_SGIS_pixel_texture not supported by this renderer.\n");
 164       exit(1);
 165    }
 166
 167    /* linear filtering looks nicer, but it's slower, since it's in software */
 168 #if 1
 169    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 170    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 171 #else
 172    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 173    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 174 #endif
 175
 176    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
 177
 178    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 179
 180    if (!LoadRGBMipmaps(TEXTURE_FILE, GL_RGB)) {
 181       printf("Error: couldn't load texture image\n");
 182       exit(1);
 183    }
 184
 185    glClearColor(0.3, 0.3, 0.4, 1.0);
 186
 187    InitImage();
 188
 189    printf("Hit SPACE to toggle pixel texgen\n");
 190 }
 191
 192
 193 int main( int argc, char *argv[] )
 194 {
 195    glutInit( &argc, argv );
 196    glutInitWindowSize( 330, 330 );
 197    glutInitWindowPosition( 0, 0 );
 198    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
 199    glutCreateWindow(argv[0] );
 200
 201    Init( argc, argv );
 202
 203    glutKeyboardFunc( Key );
 204    glutReshapeFunc( Reshape );
 205    glutDisplayFunc( Display );
 206    glutIdleFunc( Idle );
 207
 208    glutMainLoop();
 209    return 0;
 210 }