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/**
* glCopyPixels test
*
* Brian Paul
* 14 Sep 2007
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/glew.h>
#include <GL/glut.h>
#include "readtex.h"
#define IMAGE_FILE "../images/arch.rgb"
static int ImgWidth, ImgHeight;
static GLenum ImgFormat;
static GLubyte *Image = NULL;
static int WinWidth = 800, WinHeight = 800;
static int Xpos, Ypos;
static int Scissor = 0;
static float Xzoom, Yzoom;
static GLboolean DrawFront = GL_FALSE;
static GLboolean Dither = GL_TRUE;
static GLboolean Invert = GL_FALSE;
static void Reset( void )
{
Xpos = Ypos = 20;
Scissor = 0;
Xzoom = Yzoom = 1.0;
}
static void Display( void )
{
const int dx = (WinWidth - ImgWidth) / 2;
const int dy = (WinHeight - ImgHeight) / 2;
if (DrawFront) {
glDrawBuffer(GL_FRONT);
glReadBuffer(GL_FRONT);
}
else {
glDrawBuffer(GL_BACK);
glReadBuffer(GL_BACK);
}
glClear( GL_COLOR_BUFFER_BIT );
/* draw original image */
glWindowPos2iARB(dx, dy);
glDrawPixels(ImgWidth, ImgHeight, ImgFormat, GL_UNSIGNED_BYTE, Image);
if (Scissor)
glEnable(GL_SCISSOR_TEST);
if (Invert) {
glPixelTransferf(GL_RED_SCALE, -1.0);
glPixelTransferf(GL_GREEN_SCALE, -1.0);
glPixelTransferf(GL_BLUE_SCALE, -1.0);
glPixelTransferf(GL_RED_BIAS, 1.0);
glPixelTransferf(GL_GREEN_BIAS, 1.0);
glPixelTransferf(GL_BLUE_BIAS, 1.0);
}
/* draw copy */
glPixelZoom(Xzoom, Yzoom);
glWindowPos2iARB(Xpos, Ypos);
glCopyPixels(dx, dy, ImgWidth, ImgHeight, GL_COLOR);
glPixelZoom(1, 1);
glDisable(GL_SCISSOR_TEST);
if (Invert) {
glPixelTransferf(GL_RED_SCALE, 1.0);
glPixelTransferf(GL_GREEN_SCALE, 1.0);
glPixelTransferf(GL_BLUE_SCALE, 1.0);
glPixelTransferf(GL_RED_BIAS, 0.0);
glPixelTransferf(GL_GREEN_BIAS, 0.0);
glPixelTransferf(GL_BLUE_BIAS, 0.0);
}
if (DrawFront)
glFinish();
else
glutSwapBuffers();
}
static void Reshape( int width, int height )
{
WinWidth = width;
WinHeight = height;
glViewport( 0, 0, width, height );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho( 0.0, width, 0.0, height, 0.0, 2.0 );
glMatrixMode( GL_MODELVIEW );
glLoadIdentity();
glScissor(width/4, height/4, width/2, height/2);
}
static void Key( unsigned char key, int x, int y )
{
(void) x;
(void) y;
switch (key) {
case ' ':
Reset();
break;
case 'd':
Dither = !Dither;
if (Dither)
glEnable(GL_DITHER);
else
glDisable(GL_DITHER);
break;
case 'i':
Invert = !Invert;
break;
case 's':
Scissor = !Scissor;
break;
case 'x':
Xzoom -= 0.1;
break;
case 'X':
Xzoom += 0.1;
break;
case 'y':
Yzoom -= 0.1;
break;
case 'Y':
Yzoom += 0.1;
break;
case 'f':
DrawFront = !DrawFront;
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 )
{
const int step = (glutGetModifiers() & GLUT_ACTIVE_SHIFT) ? 10 : 1;
(void) x;
(void) y;
switch (key) {
case GLUT_KEY_UP:
Ypos += step;
break;
case GLUT_KEY_DOWN:
Ypos -= step;
break;
case GLUT_KEY_LEFT:
Xpos -= step;
break;
case GLUT_KEY_RIGHT:
Xpos += step;
break;
}
glutPostRedisplay();
}
static void Init( GLboolean ciMode, const char *filename )
{
printf("GL_VERSION = %s\n", (char *) glGetString(GL_VERSION));
printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));
Image = LoadRGBImage( filename, &ImgWidth, &ImgHeight, &ImgFormat );
if (!Image) {
printf("Couldn't read %s\n", filename);
exit(0);
}
if (ciMode) {
/* Convert RGB image to grayscale */
GLubyte *indexImage = (GLubyte *) 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);
Reset();
}
static void Usage(void)
{
printf("Keys:\n");
printf(" SPACE Reset Parameters\n");
printf(" Up/Down Move image up/down (SHIFT for large step)\n");
printf(" Left/Right Move image left/right (SHIFT for large step)\n");
printf(" x Decrease X-axis PixelZoom\n");
printf(" X Increase X-axis PixelZoom\n");
printf(" y Decrease Y-axis PixelZoom\n");
printf(" Y Increase Y-axis PixelZoom\n");
printf(" s Toggle GL_SCISSOR_TEST\n");
printf(" f Toggle front/back buffer drawing\n");
printf(" ESC Exit\n");
}
int main( int argc, char *argv[] )
{
GLboolean ciMode = GL_FALSE;
const char *filename = IMAGE_FILE;
int i = 1;
if (argc > i && strcmp(argv[i], "-ci")==0) {
ciMode = GL_TRUE;
i++;
}
if (argc > i) {
filename = argv[i];
}
glutInit( &argc, argv );
glutInitWindowPosition( 0, 0 );
glutInitWindowSize( WinWidth, WinHeight );
if (ciMode)
glutInitDisplayMode( GLUT_INDEX | GLUT_DOUBLE );
else
glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE);
glutCreateWindow(argv[0]);
glewInit();
Init(ciMode, filename);
Usage();
glutReshapeFunc( Reshape );
glutKeyboardFunc( Key );
glutSpecialFunc( SpecialKey );
glutDisplayFunc( Display );
glutMainLoop();
return 0;
}
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