test glDraw/Read/CopyPixels()

progs/demos/readpix.c

+/* $Id: readpix.c,v 1.1 2000/03/01 16:23:14 brianp Exp $ */
+
+/*
+ * glReadPixels and glCopyPixels test
+ * 
+ * Brian Paul   March 1, 2000  This file is in the public domain.
+ */
+
+/*
+ * $Log: readpix.c,v $
+ * Revision 1.1  2000/03/01 16:23:14  brianp
+ * test glDraw/Read/CopyPixels()
+ *
+ */
+
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <GL/glut.h>
+
+#include "../util/readtex.c"  /* a hack, I know */
+
+#define IMAGE_FILE "../images/girl.rgb"
+
+static int ImgWidth, ImgHeight;
+static GLenum ImgFormat;
+static GLubyte *Image = NULL;
+
+static int APosX, APosY;  /* simple drawpixels */
+static int BPosX, BPosY;  /* read/draw pixels */
+static int CPosX, CPosY;  /* copypixels */
+
+static GLboolean DrawFront = GL_FALSE;
+static GLboolean ScaleAndBias = GL_FALSE;
+
+static GLubyte *TempImage = NULL;
+
+
+static void
+Reset( void )
+{
+   APosX = 5;     APosY = 20;
+   BPosX = APosX + ImgWidth + 5;   BPosY = 20;
+   CPosX = BPosX + ImgWidth + 5;   CPosY = 20;
+}
+
+
+static void
+PrintString(const char *s)
+{
+   while (*s) {
+      glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
+      s++;
+   }
+}
+
+
+static void
+SetupPixelTransfer(GLboolean invert)
+{
+   if (invert) {
+      glPixelTransferf(GL_RED_SCALE, -1.0);
+      glPixelTransferf(GL_RED_BIAS, 1.0);
+      glPixelTransferf(GL_GREEN_SCALE, -1.0);
+      glPixelTransferf(GL_GREEN_BIAS, 1.0);
+      glPixelTransferf(GL_BLUE_SCALE, -1.0);
+      glPixelTransferf(GL_BLUE_BIAS, 1.0);
+   }
+   else {
+      glPixelTransferf(GL_RED_SCALE, 1.0);
+      glPixelTransferf(GL_RED_BIAS, 0.0);
+      glPixelTransferf(GL_GREEN_SCALE, 1.0);
+      glPixelTransferf(GL_GREEN_BIAS, 0.0);
+      glPixelTransferf(GL_BLUE_SCALE, 1.0);
+      glPixelTransferf(GL_BLUE_BIAS, 0.0);
+   }
+}
+
+
+static void
+Display( void )
+{
+   glClear( GL_COLOR_BUFFER_BIT );
+
+   glRasterPos2i(5, ImgHeight+25);
+   PrintString("f = toggle front/back  b = toggle scale/bias");
+
+   /* draw original image */
+   glRasterPos2i(APosX, 5);
+   PrintString("Original");
+   glRasterPos2i(APosX, APosY);
+   glEnable(GL_DITHER);
+   SetupPixelTransfer(GL_FALSE);
+   glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, Image);
+
+   /* do readpixels, drawpixels */
+   glRasterPos2i(BPosX, 5);
+   PrintString("Read/DrawPixels");
+   SetupPixelTransfer(ScaleAndBias);
+   glReadPixels(APosX, APosY, ImgWidth, ImgHeight,
+                ImgFormat, GL_UNSIGNED_BYTE, TempImage);
+   glRasterPos2i(BPosX, BPosY);
+   glDisable(GL_DITHER);
+   SetupPixelTransfer(GL_FALSE);
+   glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, TempImage);
+
+   /* do copypixels */
+   glRasterPos2i(CPosX, 5);
+   PrintString("CopyPixels");
+   glRasterPos2i(CPosX, CPosY);
+   glDisable(GL_DITHER);
+   SetupPixelTransfer(ScaleAndBias);
+   glCopyPixels(APosX, APosY, ImgWidth, ImgHeight, GL_COLOR);
+
+   if (!DrawFront)
+      glutSwapBuffers();
+}
+
+
+static void Reshape( int width, int height )
+{
+   glViewport( 0, 0, width, height );
+   glMatrixMode( GL_PROJECTION );
+   glLoadIdentity();
+   glOrtho( 0.0, width, 0.0, height, -1.0, 1.0 );
+   glMatrixMode( GL_MODELVIEW );
+   glLoadIdentity();
+}
+
+
+static void Key( unsigned char key, int x, int y )
+{
+   (void) x;
+   (void) y;
+   switch (key) {
+      case 'b':
+         ScaleAndBias = !ScaleAndBias;
+         break;
+      case 'f':
+         DrawFront = !DrawFront;
+         if (DrawFront)
+            glDrawBuffer(GL_FRONT);
+         else
+            glDrawBuffer(GL_BACK);
+         printf("glDrawBuffer(%s)\n", DrawFront ? "GL_FRONT" : "GL_BACK");
+         break;
+      case 27:
+         exit(0);
+         break;
+   }
+   glutPostRedisplay();
+}
+
+
+static void SpecialKey( int key, int x, int y )
+{
+   (void) x;
+   (void) y;
+#if 0
+   switch (key) {
+      case GLUT_KEY_UP:
+         Ypos += 1;
+         break;
+      case GLUT_KEY_DOWN:
+         Ypos -= 1;
+         break;
+      case GLUT_KEY_LEFT:
+         Xpos -= 1;
+         break;
+      case GLUT_KEY_RIGHT:
+         Xpos += 1;
+         break;
+   }
+#endif
+   glutPostRedisplay();
+}
+
+
+static void
+Init( GLboolean ciMode )
+{
+   printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
+   printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
+
+   Image = LoadRGBImage( IMAGE_FILE, &ImgWidth, &ImgHeight, &ImgFormat );
+   if (!Image) {
+      printf("Couldn't read %s\n", IMAGE_FILE);
+      exit(0);
+   }
+
+   if (ciMode) {
+      /* Convert RGB image to grayscale */
+      GLubyte *indexImage = malloc( ImgWidth * ImgHeight );
+      GLint i;
+      for (i=0; i<ImgWidth*ImgHeight; i++) {
+         int gray = Image[i*3] + Image[i*3+1] + Image[i*3+2];
+         indexImage[i] = gray / 3;
+      }
+      free(Image);
+      Image = indexImage;
+      ImgFormat = GL_COLOR_INDEX;
+
+      for (i=0;i<255;i++) {
+         float g = i / 255.0;
+         glutSetColor(i, g, g, g);
+      }
+   }
+
+   printf("Loaded %d by %d image\n", ImgWidth, ImgHeight );
+
+   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+   glPixelStorei(GL_UNPACK_ROW_LENGTH, ImgWidth);
+   glPixelStorei(GL_PACK_ALIGNMENT, 1);
+   glPixelStorei(GL_PACK_ROW_LENGTH, ImgWidth);
+
+   Reset();
+
+   TempImage = (GLubyte *) malloc(ImgWidth * ImgHeight * 4 * sizeof(GLubyte));
+   assert(TempImage);
+}
+
+
+int main( int argc, char *argv[] )
+{
+   GLboolean ciMode = GL_FALSE;
+
+   if (argc > 1 && strcmp(argv[1], "-ci")==0) {
+      ciMode = GL_TRUE;
+   }
+
+   glutInit( &argc, argv );
+   glutInitWindowPosition( 0, 0 );
+   glutInitWindowSize( 750, 250 );
+
+   if (ciMode)
+      glutInitDisplayMode( GLUT_INDEX | GLUT_DOUBLE );
+   else
+      glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
+
+   glutCreateWindow(argv[0]);
+
+   Init(ciMode);
+
+   glutReshapeFunc( Reshape );
+   glutKeyboardFunc( Key );
+   glutSpecialFunc( SpecialKey );
+   glutDisplayFunc( Display );
+
+   glutMainLoop();
+   return 0;
+}