關於Opengl中將24位BMP圖片加入一個alpha通道並實現透明的問題

#include <windows.h>
#include <GL/glut.h>
#include <GL/glaux.h>
#include <stdio.h>

#pragma comment( lib, "opengl32.lib" )// 連結時使用OpenGL32.lib
#pragma comment( lib, "glu32.lib" )// 連結時使用GLu32.lib 
#pragma comment( lib, "glaux.lib" ) // 連結時使用GLaux.lib

HWND hWnd;
HDC hDC;
HGLRC hRC=NULL;//定義渲染環境
HINSTANCE hInstance;//得到程式的樣例
RECT rect;

int sw = 600;
int sh = 600;

GLfloat aspect;
GLfloat x1=0.0;
GLfloat y1=0.0;
GLfloat xrot;// X軸旋轉
GLfloat yrot;// Y軸旋轉
GLfloat z=8.0;// 移入螢幕的深度
GLfloat x=0.0;
GLfloat y=0.0;

int LastXPos;
int LastYPos;

bool IsLBDown;
bool light;//光源-開/關
bool lp;//L鍵是否按下? 

GLfloat LightAmbient[]= { 0.5f, 0.5f, 0.5f, 1.0 }; //環境光的值
GLfloat LightDiffuse[]= { 1.0, 1.0, 1.0, 1.0 }; //散射光的值
GLfloat LightPosition[]={ 0.0, 0.0, 2.0, 1.0 }; //光照位置

GLubyte Pixel; 

GLuint texture[8];//紋理的儲存空間

AUX_RGBImageRec *TextureImage[8];//為紋理建立儲存空間

int LoadGLTextures(int i,char *FileName)//呼叫Bitmap並轉換成紋理
{
unsigned char *m_ucpData;
  unsigned int x,y,width,height;
unsigned char tempRGB;
unsigned char *buffer;
FILE *fp;
int Status=FALSE;//狀態確定
//-------------------------------讀取點陣圖，檢查錯誤。假設點陣圖不存在則退出
if(TextureImage[i]=auxDIBImageLoad(FileName))
{
width=TextureImage[i]->sizeX; 
height=TextureImage[i]->sizeY;
Status=TRUE;//將Status設為TRUE
fp=fopen(FileName,"a+b");
if(!fp){
fclose(fp);
return false;
}
//----------------------------讀取圖片RGB資訊
m_ucpData=(unsigned char *)malloc(width*height*3);
fseek(fp,54,SEEK_SET);//指標跳過檔案頭移動到指定位置
fread(m_ucpData,sizeof(unsigned char),width*height*3,fp);//從指定位置讀資料
for (int imageIdx = 0; imageIdx < (width*height*3); imageIdx+=3)
{
tempRGB = m_ucpData[imageIdx];
m_ucpData[imageIdx] = m_ucpData[imageIdx + 2];
m_ucpData[imageIdx + 2] = tempRGB;
}
//-----------------------------將RGB改動成RGBA
buffer = (unsigned char *)malloc(width*height*4);
for(x=0,y=0; x<(width*height*3); x+=3,y+=4)
{
buffer[y] = m_ucpData[x];
buffer[y+1] = m_ucpData[x+1];
buffer[y+2] = m_ucpData[x+2];
if(m_ucpData[x]==255 && m_ucpData[x+1]==255 && m_ucpData[x+2]==255)
{
buffer[y+3] = 0;
}
else
buffer[y+3] = 1;
}
//改動過的RGBA內容回寫到TextureImage[i]
TextureImage[i]->data = (unsigned char *)realloc(TextureImage[i]->data,width*height*4);
for(int a=0;a<width*height*4;a++)
{
TextureImage[i]->data[a] = buffer[a];
if((a+1)%4==1)
{
int u=TextureImage[i]->data[a];
}
}

glGenTextures(1, &texture[i]);//命名一個紋理
glBindTexture(GL_TEXTURE_2D, texture[i]);//建立紋理物件
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);//制定紋理的包裝形式，指定顏色線形過濾
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_NEAREST); //MipMapped過濾
gluBuild2DMipmaps(GL_TEXTURE_2D,3,width,height,GL_RGBA,GL_UNSIGNED_BYTE,TextureImage[i]->data);//把紋理縮放到適合大小 
}
else
{
if (TextureImage[i])//紋理是否存在
{
if (TextureImage[i]->data)
{
free(TextureImage[i]->data);//釋放紋理圖象所佔用記憶體
}
else free(TextureImage[i]);//釋放圖象結構
}
else return Status;
}
fclose(fp);
  delete buffer;
return Status;
}
void SceneInit(int w, int h)
{
LoadGLTextures(1,"obj_1.bmp");

glEnable(GL_TEXTURE_2D);

glEnable(GL_ALPHA_TEST); //透明部分測試
glAlphaFunc(GL_GREATER,0.5); 

glEnable(GL_BLEND);//啟用混合
glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA);

glShadeModel(GL_SMOOTH);//同意平滑著色
glClearColor( 0.0, 0.0, 0.0, 0.0);
}
void SceneResizeViewport(GLsizei w, GLsizei h)
{
if(h==0) 
{
h=1;
}
aspect = (GLfloat)w/(GLfloat)h;
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);//選擇投影矩陣
glLoadIdentity();//重置
gluPerspective( 45.0, aspect, 0.1f, 100.0 );//設定透視，以45度角
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

}

void SceneShow(GLvoid)//這裡進行全部的畫圖工作
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //清屏和清除深度緩衝區
glLoadIdentity();//重置當前Modelview矩陣
gluLookAt(x,y,z,x1,y1,-2.0,0.0,1.0,0.0);

  glBindTexture(GL_TEXTURE_2D, texture[1]);  
glBegin(GL_QUADS);
glNormal3f( 0.0, 0.0, 1.0);
glTexCoord2f(1.0, 0.0); glVertex3f(-0.5, -1.0, 2.0);
glTexCoord2f(1.0, 1.0); glVertex3f(-0.5, 0.0, 2.0);
glTexCoord2f(0.0, 1.0); glVertex3f( 0.5, 0.0, 2.0);
glTexCoord2f(0.0, 0.0); glVertex3f( 0.5, -1.0, 2.0);
glEnd();

glFlush();
}
//建立OPENGL窗體
void EnableOpenGL()
{
PIXELFORMATDESCRIPTOR pfd;
int iFormat;

hDC = GetDC( hWnd );

ZeroMemory( &pfd, sizeof( pfd ) );
pfd.nSize = sizeof( pfd );
pfd.nVersion = 1;
pfd.dwFlags = PFD_DRAW_TO_WINDOW |
PFD_SUPPORT_OPENGL |
PFD_DOUBLEBUFFER;
pfd.iPixelType = PFD_TYPE_RGBA;
pfd.cColorBits = 32;
pfd.cDepthBits = 32;
pfd.iLayerType = PFD_MAIN_PLANE;

iFormat = ChoosePixelFormat( hDC, &pfd );

SetPixelFormat( hDC, iFormat, &pfd );

hRC = wglCreateContext( hDC );
wglMakeCurrent( hDC, hRC );
}
void DisableOpenGL()
{
wglMakeCurrent( NULL, NULL );
wglDeleteContext( hRC );
ReleaseDC( hWnd, hDC );
}
LRESULT CALLBACK WndProc( HWND hWnd, UINT message,WPARAM wParam, LPARAM lParam )
{
switch ( message )
{
case WM_CREATE:  
GetWindowRect(hWnd, &rect);
sw = rect.right - rect.left;
sh = rect.bottom - rect.top;
SceneResizeViewport(sw, sh);
return 0;
case WM_SIZE://改變窗體的尺寸
GetWindowRect(hWnd, &rect);
sw = rect.right - rect.left;
sh = rect.bottom - rect.top;
if(sw>0 && sh>0)
SceneResizeViewport(sw, sh);
return 0;
default:
return DefWindowProc( hWnd,message, wParam, lParam );
}
}
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nCmdShow)
{
  WNDCLASS wc;
MSG msg;
bool bQuit = false;
wc.style = CS_OWNDC;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon( NULL, IDI_APPLICATION );
wc.hCursor = LoadCursor( NULL, IDC_ARROW );
wc.hbrBackground = (HBRUSH)GetStockObject( BLACK_BRUSH );
wc.lpszMenuName = NULL;
wc.lpszClassName = "Name";
RegisterClass( &wc );
hWnd = CreateWindow("Name","Animation Tech_Base on 2D Images",
WS_TILEDWINDOW | WS_VISIBLE,
GetSystemMetrics( SM_CXSCREEN )/2-sw/2,
GetSystemMetrics( SM_CYSCREEN )/2-sh/2,
sw,sh,NULL,NULL,hInstance,NULL );
ChangeDisplaySettings(NULL, 0);
ShowWindow(hWnd, SW_SHOW);
UpdateWindow(hWnd);
EnableOpenGL();
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);
SceneInit(sw, sh);
GetWindowRect(hWnd, &rect);
sw = rect.right - rect.left;
sh = rect.bottom - rect.top;
if(sw>0 && sh>0)
SceneResizeViewport(sw, sh);
while ( !bQuit )
{
if ( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) )
if ( msg.message == WM_QUIT )
bQuit = true;
else 
{
TranslateMessage( &msg );
DispatchMessage( &msg );
}
else
{
// OpenGL 動畫
SceneShow();
SwapBuffers(hDC);//重繪函式
}
}
//關閉，退出程式
DisableOpenGL();
ShowWindow (hWnd, SW_HIDE);
DestroyWindow( hWnd );
ChangeDisplaySettings(NULL, 0);
return msg.wParam;
return 0;

}

這是程式原始碼,在LoadGLTextures()函式裡面
已經對圖片的每一個象素進行讀取,加入alpha通道,並回寫到快取裡面,但是最後呼叫輸出圖片的時候卻沒有實現
debug的時候確定每一個象素點的alpha通道都按要求改動了...
請問大俠們我的問題到底出在哪裡了?