OpenGL: Image pixel manipulation

#define Glut_disable_atexit_hack #include <Windows.h> #include <stdio.h> #include <gl/glut.h> #
Include <gl/glaux.h> #pragma comment (lib, "Glaux.lib") #pragma comment (lib, "Glut32.lib") aux_rgbimagerec* Image;
Glint iwidth,iheight,imode=1;

Glubyte* Pimage;
	void Menucreate (void) {Glutaddmenuentry ("normal display", 1);
	Glutaddmenuentry ("Flip Image", 2);
	Glutaddmenuentry ("Reduced image", 3);
	Glutaddmenuentry ("Red Channel", 4);
	Glutaddmenuentry ("Green channel", 5);
	Glutaddmenuentry ("Blue channel", 6);
	Glutaddmenuentry ("Grayscale image", 7);

	Glutaddmenuentry ("Invert color", 8);
Glutattachmenu (Glut_right_button);

	} void initialization (void) {Glclearcolor (0,0,0,1);

	Menucreate ();
	Glpixelstorei (gl_unpack_alignment, 1);
	Image = Auxdibimageload ("11.bmp");
	Iwidth = image->sizex;
	Iheight = image->sizey;
Pimage = image->data;

	} void Ondisplay (void) {glclear (gl_color_buffer_bit);
	Glbyte *pmodified = NULL;
	Glfloat invert[256];

	Glint I;

	Glrasterpos2i (0, 0); Switch (iMode) {case 2:glpixelzoom ( -1.0f, -1.0f);
		Glrasterpos2i (IWidth-1, iHeight-1);

	Break
		Case 3:glpixelzoom (0.5f, 0.5f);

	Break
		Case 4:glpixeltransferf (Gl_red_scale, 1.0f);
		Glpixeltransferf (Gl_green_scale, 0.0f);
		Glpixeltransferf (Gl_blue_scale, 0.0f);

	Break
		Case 5:glpixeltransferf (Gl_red_scale, 0.0f);
		Glpixeltransferf (Gl_green_scale, 1.0f);
		Glpixeltransferf (Gl_blue_scale, 0.0f);

	Break
		Case 6:glpixeltransferf (Gl_red_scale, 0.0f);
		Glpixeltransferf (Gl_green_scale, 0.0f);
		Glpixeltransferf (Gl_blue_scale, 1.0f);

	Break
		Case 7:gldrawpixels (Iwidth,iheight, Gl_rgb, Gl_unsigned_byte, pimage);

		Pmodified = (glbyte*) New glbyte[iwidth * iheight];
		Glpixeltransferf (Gl_red_scale, 0.3f);
		Glpixeltransferf (Gl_green_scale, 0.59f);

		Glpixeltransferf (Gl_blue_bits, 0.11f);
		Glreadpixels (0, 0, iwidth, iheight, Gl_luminance, Gl_unsigned_byte, pmodified);
		Glpixeltransferf (Gl_red_scale, 1.0f);
		Glpixeltransferf (Gl_green_scale, 1.0f);
		Glpixeltransferf (Gl_blue_scale, 1.0f); Break;
		Case 8:invert[0] = 1.0f;
		for (i = 1; i < i++) {Invert[i] = 1.0f-(1.0f/255.0f * glfloat (i));
		} GLPIXELMAPFV (Gl_pixel_map_r_to_r, 255, invert);
		GLPIXELMAPFV (Gl_pixel_map_g_to_g, 255, invert);
		GLPIXELMAPFV (Gl_pixel_map_b_to_b, 255, invert);
		Glpixeltransferf (gl_map_color,gl_true);

	Break
	Case 1:default:break;
	} if (pmodified = = NULL) {gldrawpixels (iwidth, Iheight, Gl_rgb,gl_unsigned_byte, pimage);
		} else {gldrawpixels (iwidth, Iheight, Gl_luminance, Gl_unsigned_byte, pmodified);
	delete [] pmodified;
	} glpixeltransferi (Gl_map_color, Gl_false);
	Glpixeltransferf (Gl_red_scale, 1.0f);
	Glpixeltransferf (Gl_green_scale, 1.0f);
	Glpixeltransferf (Gl_blue_scale, 1.0f);

	Glpixelzoom (1.0f, 1.0f);
Glutswapbuffers ();

	} void Onreshape (int w,int h) {glfloat aspectratio= (glfloat) w/(Glfloat) h;//calculates the aspect ratio of the window glfloat winwidth,winheight;

	Glviewport (0, 0, W, h);
	Glmatrixmode (gl_projection);


	Glloadidentity ();              if (w <= h) {                 Calculates the width and height of the drawing area according to aspect ratio winwidth = 400;
	winheight = * Aspectratio;
		} else {winwidth = Aspectratio *;
	Winheight= 400;


	} gluortho2d (0, winwidth, 0, winheight);
	Glmatrixmode (Gl_modelview);
Glloadidentity ();

	} void OnMenu (int value) {IMode = value;
Glutpostredisplay ();
	} void Main (int argc,char* argv[]) {glutinit (&AMP;ARGC,ARGV); Glutinitdisplaymode (glut_double | Glut_rgb |
	Glut_depth);
	Glutinitwindowsize (400, 400);

	Glutcreatewindow ("EXAM703");
	Glutcreatemenu (OnMenu);
	Glutdisplayfunc (Ondisplay);

	Glutreshapefunc (Onreshape);
	Initialization ();
Glutmainloop (); }

Operation Result: