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/**
* Dissolve between two images using randomized stencil buffer
* and varying stencil ref.
*
* Brian Paul
* 29 Jan 2010
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#include "readtex.h"
#define FILE1 "../images/bw.rgb"
#define FILE2 "../images/arch.rgb"
static int Win;
static int WinWidth = 400, WinHeight = 400;
static GLboolean Anim = GL_TRUE;
static int ImgWidth[2], ImgHeight[2];
static GLenum ImgFormat[2];
static GLubyte *Image[2];
static GLfloat ScaleX[2], ScaleY[2];
static GLubyte StencilRef = 0;
static void
Idle(void)
{
StencilRef = (GLint) (glutGet(GLUT_ELAPSED_TIME) / 10);
glutPostRedisplay();
}
static void
RandomizeStencilBuffer(void)
{
GLubyte *b = malloc(WinWidth * WinHeight);
int i;
for (i = 0; i < WinWidth * WinHeight; i++) {
b[i] = rand() & 0xff;
}
glStencilFunc(GL_ALWAYS, 0, ~0);
glPixelZoom(1.0, 1.0);
glDrawPixels(WinWidth, WinHeight, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, b);
free(b);
}
static void
Draw(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glPixelZoom(ScaleX[0], ScaleY[0]);
glStencilFunc(GL_LESS, StencilRef, ~0);
glDrawPixels(ImgWidth[0], ImgHeight[0], ImgFormat[0], GL_UNSIGNED_BYTE, Image[0]);
glPixelZoom(ScaleX[1], ScaleY[1]);
glStencilFunc(GL_GEQUAL, StencilRef, ~0);
glDrawPixels(ImgWidth[1], ImgHeight[1], ImgFormat[1], GL_UNSIGNED_BYTE, Image[1]);
glutSwapBuffers();
}
static void
Reshape(int width, int height)
{
WinWidth = width;
WinHeight = height;
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0, 0.0, -15.0);
RandomizeStencilBuffer();
ScaleX[0] = (float) width / ImgWidth[0];
ScaleY[0] = (float) height / ImgHeight[0];
ScaleX[1] = (float) width / ImgWidth[1];
ScaleY[1] = (float) height / ImgHeight[1];
}
static void
Key(unsigned char key, int x, int y)
{
(void) x;
(void) y;
switch (key) {
case 'a':
Anim = !Anim;
if (Anim)
glutIdleFunc(Idle);
else
glutIdleFunc(NULL);
break;
case 27:
glutDestroyWindow(Win);
exit(0);
break;
}
glutPostRedisplay();
}
static void
Init(void)
{
Image[0] = LoadRGBImage(FILE1, &ImgWidth[0], &ImgHeight[0], &ImgFormat[0]);
if (!Image[0]) {
printf("Couldn't read %s\n", FILE1);
exit(0);
}
Image[1] = LoadRGBImage(FILE2, &ImgWidth[1], &ImgHeight[1], &ImgFormat[1]);
if (!Image[1]) {
printf("Couldn't read %s\n", FILE1);
exit(0);
}
glEnable(GL_STENCIL_TEST);
glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
}
int
main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(WinWidth, WinHeight);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH | GLUT_STENCIL);
Win = glutCreateWindow(argv[0]);
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Draw);
if (Anim)
glutIdleFunc(Idle);
Init();
glutMainLoop();
return 0;
}
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