[英]Convert C uint8_t pointer to C# byte array
I have exported the following C function to be invoked in a DLL file. 我已经导出了要在DLL文件中调用的以下C函数。
uint8_t* _stdcall GetCurrentImage();
Now I want to call this function in C# to get a bitmap Image. 现在,我想在C#中调用此函数以获取位图图像。 How can I do this?
我怎样才能做到这一点?
Thanks in advance! 提前致谢!
You will need to know the exact number of bytes returned and the bitmap dimensions (height, width and encoding). 您将需要知道返回的确切字节数和位图尺寸(高度,宽度和编码)。 Then you can declare it in C# as:
然后,您可以在C#中将其声明为:
[DllImport("yourlib.dll")]
private static extern IntPtr GetCurrentImage();
The IntPtr you get from that can be used with Marshal.Copy
, to get the raw bytes: 您从中获得的IntPtr可以与
Marshal.Copy
一起使用,以获取原始字节:
byte[] buffer = new byte[length];
IntPtr beginPtr = GetCurrentImage();
Marshal.Copy(beginPtr, buffer,0,length);
Finally, declare a Bitmap with the dimensions of your image and the PixelFormat used (if it is a non-standard pixelformat, you might have to do some conversion yourself). 最后,声明一个具有图像尺寸和所用PixelFormat的Bitmap (如果它是非标准的pixelformat,则可能需要自己进行一些转换)。 Then you can copy the data into the raw bitmap bytes, by using LockBits to get a BitmapData instance that points to the raw bitmap data.
然后,您可以使用LockBits获取指向原始位图数据的BitmapData实例,将数据复制到原始位图字节中。
If you want to keep on working in an unsafe context even in C#, you can also simplify everything by bypassing Marshal and IntPtrs as follows: 如果要即使在C#中也要在不安全的上下文中继续工作,则还可以通过绕过Marshal和IntPtrs来简化一切,如下所示:
[DllImport("Library.dll")]
internal static unsafe extern Byte* GetCurrentImage();
Keep in mind that's always good practice to insert all of your imports in a static class called NativeMethods and declare them as internal. 请记住,将所有导入都插入到名为NativeMethods的静态类中并将它们声明为内部是一种好习惯。
The common strategy for things like this is to pass in a buffer and have the function fill the buffer. 诸如此类的通用策略是传入缓冲区并让函数填充缓冲区。 Otherwise you run into trouble with disposing of the memory allocated;
否则,您将在处理分配的内存时遇到麻烦; in other words, you will have a memory leak.
换句话说,您将发生内存泄漏。
So you should have C functions like this... 所以你应该有这样的C函数...
uint32_t _stdcall GetCurrentImageSize();
void _stdcall GetCurrentImage(uint8_t* buffer, int offset, int bufferSize);
And then in C# you would do something like... 然后在C#中,您将执行以下操作:
var buffer = new byte [ GetCurrentImageSize() ];
fixed (byte* b = &buffer[0])
GetCurrentImage(b, 0, buffer.Length);
// 'buffer' now contains the image
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