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Operations on Graphic Objects
Once an application creates a display or printer device context, it can begin
drawing on the associated device or, in the case of the memory device context,
it can begin drawing on the bitmap stored in memory. However, before drawing
begins and sometimes while drawing is in progress, it is often necessary to
replace the default objects with new objects.
An application can examine a default object's attributes by calling the GetCurrentObject and GetObject functions. The GetCurrentObject function returns a handle identifying the current pen, brush, palette,
bitmap, or font, and the GetObject function initializes a structure containing that object's attributes.
Some printers provide resident pens, brushes, and fonts that can be used to
improve drawing speed in an application. Two functions can be used to enumerate
these objects: EnumObjects and EnumFontFamilies. If the application must enumerate resident pens or brushes, it can call the EnumObjects function to examine the corresponding attributes. If the application must
enumerate resident fonts, it can call the EnumFontFamilies function (which can also enumerate GDI fonts).
Once an application determines that a default object needs replacing, it
creates a new object by calling one of the following creation functions.
Graphic object
| Function
| Bitmap
| CreateBitmap, CreateBitmapIndirect, CreateCompatibleBitmap, CreateDiscardableBitmap, CreateDIBitmap
| Brush
| CreateBrushIndirect, CreateDIBPatternBrush, CreateDIBPatternBrushPt, CreateHatchBrush, CreatePatternBrush, CreateSolidBrush
| Color Palette
| CreatePalette
| Font
| CreateFont, CreateFontIndirect
| Pen
| CreatePen, CreatePenIndirect, ExtCreatePen
| Region
| CreateEllipticRgn, CreateEllipticRgnIndirect, CreatePolygonRgn, CreatePolyPolygonRgn, CreateRectRgn, CreateRectRgnIndirect, CreateRoundRectRgn
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Each of these functions returns a handle identifying a new object. After an
application retrieves a handle, it must call the SelectObject function to replace the default object. However, the application should save
the handle identifying the default object and use this handle to replace the
new object when it is no longer needed. When the application finishes drawing
with the new object, it must restore the default object by calling the SelectObject function and delete the new object by calling the DeleteObject function. Failing to delete objects causes serious performance problems.
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.Net is powerful, but not all-powerful, so sometimes we need to use Win32 API for our .Net applications. It's simple enough with Platform Invoke if you have Win32 skill, but we do not always have time to dig the ancient documentation, declare the special types that are compatible with Win32, find the values of the Win32's constants and so on. Nostalgia .Net offers several simple-to-use classes, and components that will allow you to forget about the headache of Win32 and just use the power of Win32 in your application the same way as you use the native. Net classes. More » |
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All the contacts and projectsDmitry Vasiliev (just.dmitry)
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