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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 "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;
}
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