initial check-in

progs/demos/pixeltex.c

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+/*
+ * GL_SGIS_pixel_texture demo
+ *
+ * Brian Paul
+ * 6 Apr 2000
+ *
+ * Copyright (C) 2000  Brian Paul   All Rights Reserved.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+
+/*
+ * How this works:
+ * 1. We load the image into a 2D texture.
+ * 2. We generate a sequence of RGB images in which the R component
+ *    is really the S texture coordinate and the G component is really
+ *    the T texture coordinate.
+ *    By warping the mapping from R to S and G to T we can get non-linear
+ *    distortions.
+ * 3. Draw the warped image (a 2-D warping function) with pixel texgen
+ *    enabled.
+ * 4. Loop over the warped images to animate.
+ *
+ * The pixel texgen extension can also be used to do color-space
+ * conversions.  For example, we could convert YCR to RGB with a
+ * 3D texture map which takes YCR as the S,T,R texture coordinate and
+ * returns RGB texel values.
+ *
+ * You can use this extension in (at least) two ways:
+ * 1. glDrawPixels w/ color space conversion/warping
+ * 2. glDrawPixels to spatially warp another image in texture memory
+ *
+ * We're basically using glDrawPixels to draw a texture coordinate image.
+ */
+
+
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <GL/glut.h>
+#include <GL/glext.h>
+#include "../util/readtex.c"   /* I know, this is a hack. */
+
+#define TEXTURE_FILE "../images/girl.rgb"
+
+static int ImgWidth = 300, ImgHeight = 300;
+#define FRAMES 20
+static GLubyte *ImgData[FRAMES];
+static GLint Frame = 0;
+
+static GLboolean TextureFlag = GL_TRUE;
+
+
+static void Display( void )
+{
+   glClear( GL_COLOR_BUFFER_BIT );
+
+   if (TextureFlag) {
+      glEnable(GL_PIXEL_TEXTURE_SGIS);
+      glEnable(GL_TEXTURE_2D);
+   }
+   else {
+      glDisable(GL_PIXEL_TEXTURE_SGIS);
+      glDisable(GL_TEXTURE_2D);
+   }
+
+   glColor3f(1, 1, 1);
+   glRasterPos2f(10, 10);
+   glDrawPixels(ImgWidth, ImgHeight, GL_RGB, GL_UNSIGNED_BYTE, ImgData[Frame]);
+
+   glutSwapBuffers();
+}
+
+
+static void Reshape( int width, int height )
+{
+   glViewport( 0, 0, width, height );
+   glMatrixMode( GL_PROJECTION );
+   glLoadIdentity();
+   glOrtho(0, width, 0, height, -1, 1);
+   glMatrixMode( GL_MODELVIEW );
+   glLoadIdentity();
+}
+
+
+static void Key( unsigned char key, int x, int y )
+{
+   (void) x;
+   (void) y;
+   switch (key) {
+      case ' ':
+         TextureFlag = !TextureFlag;
+         break;
+      case 27:
+         exit(0);
+         break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void Idle(void)
+{
+   Frame++;
+   if (Frame >= FRAMES)
+      Frame = 0;
+   glutPostRedisplay();
+}
+
+
+static GLubyte warp(GLfloat s, int frame)
+{
+   static const GLfloat PI = 3.14159265;
+   static int halfFrame = FRAMES / 2;
+   GLfloat y, weight, v;
+   if (frame >= halfFrame)
+      frame = halfFrame - (frame - halfFrame);
+   y = sin(s * PI);
+   weight = (float) frame / (FRAMES-1);
+   v = y * (0.8 * weight + 0.2);
+   return (GLint) (v * 255.0F);
+}
+
+
+static void InitImage(void)
+{
+   int i, j, frame;
+   for (frame = 0; frame < FRAMES; frame++) {
+      ImgData[frame] = (GLubyte *) malloc(ImgWidth * ImgHeight * 3);
+      for (i = 0; i < ImgHeight; i++) {
+         for (j = 0; j < ImgWidth; j++) {
+            GLubyte *pixel = ImgData[frame] + (i * ImgWidth + j) * 3;
+            pixel[0] = warp((float) j / (ImgWidth - 0), frame);
+            pixel[1] = warp((float) i / (ImgHeight - 0), frame);
+            pixel[2] = 0.0;
+         }
+      }
+   }
+}
+
+
+static void Init( int argc, char *argv[] )
+{
+   const char *exten = (const char *) glGetString(GL_EXTENSIONS);
+   if (!strstr(exten, "GL_SGIS_pixel_texture")) {
+      printf("Sorry, GL_SGIS_pixel_texture not supported by this renderer.\n");
+      exit(1);
+   }
+
+   /* linear filtering looks nicer, but it's slower, since it's in software */
+#if 1
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+#else
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+#endif
+
+   glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
+
+   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+
+   if (!LoadRGBMipmaps(TEXTURE_FILE, GL_RGB)) {
+      printf("Error: couldn't load texture image\n");
+      exit(1);
+   }
+
+   glClearColor(0.3, 0.3, 0.4, 1.0);
+
+   InitImage();
+
+   printf("Hit SPACE to toggle pixel texgen\n");
+}
+
+
+int main( int argc, char *argv[] )
+{
+   glutInit( &argc, argv );
+   glutInitWindowSize( 330, 330 );
+   glutInitWindowPosition( 0, 0 );
+   glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
+   glutCreateWindow(argv[0] );
+
+   Init( argc, argv );
+
+   glutKeyboardFunc( Key );
+   glutReshapeFunc( Reshape );
+   glutDisplayFunc( Display );
+   glutIdleFunc( Idle );
+
+   glutMainLoop();
+   return 0;
+}