A C# Sample Code/Article Extending the Capabilities of GDI+ in C# (.NET)

C#中支持选择区域图片的GDI+源代码

2007年12月12日

C#, .NET, WinXP, VistaVS2005, Dev

C#中的GDI+有一个很大的缺陷，那就是不能够想MFC中一样，选择图像中的一个区域，本程序给你解决这个问题。最主要是通过pInvoke调用DrawDragRect系统API。

相关知识

Inside the CDrawDragRect class the function void DrawDragRect(MouseEventArgs e) is the one responsible for this feature. This is called in response to the OnMouseMove(MouseEventArgs e) event of the form. As one can see, Win32 APIs (through pInvoke) are generously used in the implementation of this feature.

The DrawDragRect(MouseEventArgs e) API first goes on to create 4 Windows regions:

rgnOld
rgnNew
rgnDiff
rgnDiffOld

源代码原文下载：

A C# Sample Code/Article Extending the Capabilities of GDI+ in C# (.NET) In imaging applications like Adobe's Photoshop, Google's Picasa or Coral's Paint Shop Pro, there is always a need to select a part of image. Maybe the user wants to enlarge a section of image, or maybe the user wants to process a selected region of an image (see Figure 1 below). Imaging applications which are written/ported to .NET language like C# are at a great loss as there is no DrawDragRect (…) API in C# or other .NET Languages. The problem is compounded, as there is no Win32 API that can be used through pInvoke, (a commonly used technique to invoke win32 APIs from .NET languages). This paper gives an implementation of the DrawDragRect (…) API written in C# that can be incorporated very easily into your C# forms programs or any other .NET form based programs.

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