progs/demos: new image dissolve demo

Dissolve between two images using a random pattern in the stencil
buffer and a varying stencil ref value.

progs/demos/Makefile

@@ -20,6 +20,7 @@ PROGS = \
 	copypix \
 	cubemap \
 	dinoshade \
+	dissolve \
 	drawpix \
 	engine \
 	fbo_firecube \

progs/demos/SConscript

@@ -8,6 +8,7 @@ progs = [
     'clearspd',
     'copypix',
     'cubemap',
+    'dissolve',
     'drawpix',
     'engine',
     'fbo_firecube',

progs/demos/dissolve.c

@@ -0,0 +1,158 @@
+/**
+ * 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;
+}