如何正确地将托管位图转换为非托管位图？

Question

我想在Visual C++ .NET 2008中使用OpenGL创建一个带纹理的立方体。 在使用GLU进行一些Googgling之后，我发现我必须使用gluBuild2DMipmaps。

的问题是，我读使用System ::绘图:: Bitmap.FromFile（）

位图现在，我如何通过这个管理Bitmap对象gluBuild2DMipmaps，其接受常量无效*参数???

我已经在使用这些代码尝试LockBits：

BYTE * data; 
/*ambil raw data*/ 
System::Drawing::Rectangle rect = System::Drawing::Rectangle(0,0,b->Width,b->Height); 
System::Drawing::Imaging::BitmapData^bitmapData; 
    b->LockBits(
     rect, 
     System::Drawing::Imaging::ImageLockMode::ReadWrite, 
     b->PixelFormat ,bitmapData); 

    ::memcpy(data,bitmapData->Scan0.ToPointer(),b->Width * b->Height); 
gluBuild2DMipmaps(GL_TEXTURE_2D, 3, width, height, 
        GL_RGB, GL_UNSIGNED_BYTE, data); 

使用和24bpp BMP文件，它停留在与消息System.ArgumentException行lockbit：附加信息：参数无效。

我做错了什么？

---

我刚找到正确的解决方案。这是因为几个问题：

1. 我使用了错误的重载函数。看到我如何调用lockBits
2. 我不是初始化指针dataBitmap。
3. 此外，由于GLuint * texture;是一个托管指针，我必须使用pin_pointer将其转换为非托管指针。

谢谢，这是正确的方法：

void CBox::LoadTextureRaw(String^filename, int wrap) 
{ 
    //GLuint texture; 

    System::Drawing::Bitmap^bitmap = gcnew Bitmap(filename); 
    int h = bitmap->Height; 
    int w = bitmap->Width; 
    int s = w * h; 
    dataTexture = new BYTE[s * 3]; 

    System::Drawing::Rectangle rect = System::Drawing::Rectangle(0,0,bitmap->Width,bitmap->Height); 
    System::Drawing::Imaging::BitmapData^bitmapData = 
     bitmap->LockBits(rect,System::Drawing::Imaging::ImageLockMode::ReadWrite , System::Drawing::Imaging::PixelFormat::Format24bppRgb); 

    ::memcpy(dataTexture,bitmapData->Scan0.ToPointer(),s); 


    bitmap->UnlockBits(bitmapData); 
    pin_ptr<GLuint*> pt = &texture;//pin managed pointer, to be unmanaged... asyeeeem 
    **pt = gluBuild2DMipmaps(GL_TEXTURE_2D, 3, w, h,GL_RGB, GL_UNSIGNED_BYTE, dataTexture);  
} 

Answer 1

我用下面的代码复制位图数据：

Image image = null; 
Bitmap iBitmap = new Bitmap(fs); 
BitmapData iBitmapData; 
GCHandle hImageData; 

if ((iBitmap.Flags & (int)ImageFlags.ColorSpaceRgb) != 0) { 
    switch (iBitmap.PixelFormat) { 
     case PixelFormat.Format1bppIndexed: 
     case PixelFormat.Format4bppIndexed: 
     case PixelFormat.Format8bppIndexed: 
      // Allocate image raster 
      image = new RasterImage<ColorBGR8>(iBitmap.Width, iBitmap.Height); 
      break; 
     case PixelFormat.Format16bppRgb565: 
      // Allocate image raster 
      image = new RasterImage<ColorBGR16>(iBitmap.Width, iBitmap.Height); 
      break; 
     case PixelFormat.Format24bppRgb: 
      // Allocate image raster 
      image = new RasterImage<ColorBGR24>(iBitmap.Width, iBitmap.Height); 
      break; 
     case PixelFormat.Format32bppRgb: 
      // Allocate image raster 
      image = new RasterImage<ColorBGR32>(iBitmap.Width, iBitmap.Height); 
      break; 
     case PixelFormat.Format32bppArgb: 
      // Allocate image raster 
      image = new RasterImage<ColorABGR32>(iBitmap.Width, iBitmap.Height); 
      break; 
     default: 
      throw new Exception("Image RGB pixel format not supported"); 
    } 
} else if ((iBitmap.Flags & (int)ImageFlags.ColorSpaceGray) != 0) { 
    switch (iBitmap.PixelFormat) { 
     case PixelFormat.Format1bppIndexed: 
     case PixelFormat.Format4bppIndexed: 
     case PixelFormat.Format8bppIndexed: 
      // Allocate image raster 
      image = new RasterImage<ColorY8>(iBitmap.Width, iBitmap.Height); 
      break; 
     default: 
      throw new Exception("Image GRAY pixel format not supported"); 
    } 

    if (RenderContext.Caps.TextureSwizzle == false) { 
     throw new Exception("unable to load GRAY pixel format image (ARB_texture_swizzle extension not supported)"); 
    } 
} else if ((iBitmap.Flags & (int)ImageFlags.ColorSpaceYcbcr) != 0) { 
    throw new Exception("Image YCbCr pixel format not supported"); 
} else if ((iBitmap.Flags & (int)ImageFlags.ColorSpaceYcck) != 0) { 
    throw new Exception("Image YCCK pixel format not supported"); 
} else if ((iBitmap.Flags & (int)ImageFlags.ColorSpaceCmyk) != 0) { 
    throw new Exception("Image CMYK pixel format not supported"); 
} else 
    throw new Exception("Image pixel format not supported"); 

// Obtain source and destination data pointers 
iBitmapData = iBitmap.LockBits(new Rectangle(0, 0, iBitmap.Width, iBitmap.Height), ImageLockMode.ReadOnly, iBitmap.PixelFormat); 
hImageData = GCHandle.Alloc(image.GetPixelData(), GCHandleType.Pinned); 

    // Alternative without using custom Image class: 
    //T[,] buffer = new ColorRGB24[iBitmap.Width, iBitmap.Height]; 
    //hImageData = GCHandle.Alloc(buffer, GCHandleType.Pinned); 

// Copy Bitmap data to Image 
memcpy(hImageData.AddrOfPinnedObject(), iBitmapData.Scan0, iBitmapData.Stride*iBitmapData.Height); 

hImageData.Free(); 
iBitmap.UnlockBits(iBitmapData); 

return (image); 

你可以注意到，我不得不的P/Invoke memcpy例程来复制锁定的内存。

的图片类）在我的项目，它定义了方法GetPixelData（定义的类作为一个简单的程序返回一个T [，]，其中Ť是像下面

的结构

[StructLayout(LayoutKind.Sequential, Pack = 1)] 
public struct ColorRGB24 : IColorRGB<byte> 
{ 
    public byte r; 
    public byte g; 
    public byte b; 
} 

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阅读以下报价：

Using System.Drawing.Imaging.PixelFormat values, such as Indexed and Gdi, will throw an System.ArgumentException 

因此，请确保没有索引或Gdi像素格式值。