unit FrameBufferUnit;

interface

uses
 Windows, SysUtils, Graphics, GL, GLu, GLext;

type
 TFrameBuffer = class
 private
   width   : Integer;
   height  : Integer;
   frameb  : GLuint;
   depthb  : GLuint;
   texture : GLuint;
   ftex    : boolean;
 public
   constructor Create(const nWidth,nHeight:Integer;ctexture:Integer = 0 );
   destructor Destroy;override;
   procedure BindFrameBuffer;
   procedure UnbindFrameBuffer;
   function GetBitmap:TBitmap;
   procedure AttachTexture;
   procedure DettachTexture;    
 end;

implementation

{ TFrameBuffer }

type
 TRGBLine = array [0..1023] of TRGBTriple;
 PRGBLine = ^TRGBLine;

procedure TFrameBuffer.AttachTexture;
begin
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT,GL_COLOR_ATTACHMENT0_EXT,GL_TEXTURE _2D,texture,0);
end;

procedure TFrameBuffer.BindFrameBuffer;
begin
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT,frameb);
end;

constructor TFrameBuffer.Create(const nWidth, nHeight: Integer;ctexture:Integer);
var
 res   : Integer;
 ww,hh : Integer;
begin
Width:=nWidth;
Height:=nHeight;
{ ww:=1;
while ww<Width do
 ww:=ww*2;
hh:=1;
while hh<Height do
 hh:=hh*2;}
ww:=Width;
hh:=Height;
ftex:=ctexture<>0;
if ftex then
 texture:=ctexture
else
 glGenTextures(1,@texture);
glBindTexture(GL_TEXTURE_2D,texture);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR_MIPMAP_LINEAR);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D,GL_GENERATE_MIPMAP,0);
glTexImage2D(GL_TEXTURE_2D,0,GL_RGBA8,ww,hh,0,GL_RGBA,GL_UNSIGNED_BYTE,nil);
glBindTexture(GL_Texture_2D,0);
glGenFramebuffersEXT(1,@frameb);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT,frameb);
glGenRenderbuffersEXT(1,@depthb);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT,depthb);
glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT,GL_DEPTH_COMPONENT,width,height);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT,0);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT,GL_COLOR_ATTACHMENT0_EXT,GL_TEXTURE _2D,texture,0);
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT,GL_DEPTH_ATTACHMENT_EXT,GL_RENDE RBUFFER_EXT,depthb);
res:=glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
if res<>GL_FRAMEBUFFER_COMPLETE_EXT then
 raise Exception.Create('frame buffer error');
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT,0);
end;

destructor TFrameBuffer.Destroy;
begin
DettachTexture;
glDeleteFramebuffersEXT(1,@frameb);
glDeleteRenderbuffersEXT(1,@depthb);
if not ftex then
 glDeleteTextures(1,@texture);
inherited;
end;

procedure TFrameBuffer.DettachTexture;
begin
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT,GL_COLOR_ATTACHMENT0_EXT,GL_TEXTURE _2D,0,0);
end;

function TFrameBuffer.GetBitmap: TBitmap;
var
 buf : Pointer;
 l   : PRGBLine;
 b   : ^TRGBTriple;
 i,j : Integer;
 h,w : Integer;
function PtrAllign(APointer:Pointer; bytes: cardinal):Pointer;
begin
 Result := Ptr(cardinal(APointer) + (bytes-cardinal(APointer) mod bytes) mod bytes);
end;
begin
w:=width;
h:=height;
result:=TBitmap.Create;
result.PixelFormat:=pf24bit;
result.Width:=w;
result.Height:=h;
GetMem(buf,w*h*3);
glBindTexture(GL_TEXTURE_2D,texture);
ZeroMemory(buf,w*h*3);
glGetTexImage(GL_TEXTURE_2D,0,GL_RGB,GL_UNSIGNED_BYTE,buf);
glBindTexture(GL_TEXTURE_2D,0);
b:=buf;
for i:=h-1 downto 0 do
begin
  l:=result.ScanLine[i];
  for j:=0 to w-1 do
  begin
    l[j].rgbtBlue:=b.rgbtRed;
    l[j].rgbtGreen:=b.rgbtGreen;
    l[j].rgbtRed:=b.rgbtBlue;
    Inc(b);
  end;
  b:=PtrAllign(b,4);
end;
FreeMemory(buf);
end;

procedure TFrameBuffer.UnbindFrameBuffer;
begin
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT,0);
end;

end.

int y;
int w = m_ScreenWidth;
int h = m_ScreenHeight;
unsigned char *pPixelData = (unsigned char *)mem_alloc(w*(h+1)*3, 1);
unsigned char *pTempRow = pPixelData+w*h*3;
GLint Alignment;
glGetIntegerv(GL_PACK_ALIGNMENT, &Alignment);
glPixelStorei(GL_PACK_ALIGNMENT, 1);
glReadPixels(0,0, w, h, GL_RGB, GL_UNSIGNED_BYTE, pPixelData);
glPixelStorei(GL_PACK_ALIGNMENT, Alignment);

// flip the pixel because opengl works from bottom left corner
for(y = 0; y < h/2; y++)
{
 mem_copy(pTempRow, pPixelData+y*w*3, w*3);
 mem_copy(pPixelData+y*w*3, pPixelData+(h-y-1)*w*3, w*3);
 mem_copy(pPixelData+(h-y-1)*w*3, pTempRow,w*3);
}