儲存OpenGL視窗每一幀程式碼段（freeimage庫）

char screenshotOrder[10];
sprintf_s(screenshotOrder, "%05d", screenshotNum);
string screenshotName = screenshotOrder;
screenshotName = "renderOutputs/anim" + screenshotName + ".bmp";//檔名
//設定長寬，需要修改其位置數值
unsigned char *mpixels = new unsigned char[900 * 900 * 4];
glReadBuffer(GL_FRONT);
glReadPixels(0, 0, 900, 900, GL_RGBA, GL_UNSIGNED_BYTE, mpixels);
glReadBuffer(GL_BACK);
for (int i = 0; i < (int)900 * 900 * 4; i += 4){
    mpixels[i] ^= mpixels[i + 2] ^= mpixels[i] ^= mpixels[i + 2];
}
FIBITMAP* bitmap = FreeImage_Allocate(900, 900, 32, 8, 8, 8);
for (int y = 0; y < FreeImage_GetHeight(bitmap); y++)
{
      BYTE *bits = FreeImage_GetScanLine(bitmap, y);
      for (int x = 0; x < FreeImage_GetWidth(bitmap); x++)
      {
           bits[0] = mpixels[(y * 900 + x) * 4 + 0];//900為長
           bits[1] = mpixels[(y * 900 + x) * 4 + 1];
           bits[2] = mpixels[(y * 900 + x) * 4 + 2];
           bits[3] = 255;
           bits += 4;

      }
}
bool bSuccess = FreeImage_Save(FIF_PNG, bitmap, screenshotName.c_str(), PNG_DEFAULT);
if (bSuccess == false)
      cout << "圖片儲存失敗" << endl;
FreeImage_Unload(bitmap);
delete[] mpixels;
screenshotNum++;//設定一個全域性變數第幾幀