86 lines
3.4 KiB
TeX
86 lines
3.4 KiB
TeX
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\section{Bitmaps overview}\label{wxbitmapoverview}
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Classes: \helpref{wxBitmap}{wxbitmap}, \helpref{wxBitmapHandler}{wxbitmaphandler}, \helpref{wxIcon}{wxicon}, \helpref{wxCursor}{wxcursor}.
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The wxBitmap class encapsulates the concept of a platform-dependent bitmap,
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either monochrome or colour. Platform-specific methods for creating a
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wxBitmap object from an existing file are catered for, and
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this is an occasion where conditional compilation will sometimes be
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required.
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A bitmap created dynamically or loaded from a file can be selected
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into a memory device context (instance of \helpref{wxMemoryDC}{wxmemorydc}). This
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enables the bitmap to be copied to a canvas or memory device context
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using \helpref{wxDC::Blit}{wxdcblit}, or to be used as a drawing surface. The {\bf
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wxToolBarSimple} class is implemented using bitmaps, and the toolbar demo
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shows one of the toolbar bitmaps being used for drawing a miniature
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version of the graphic which appears on the main canvas.
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See \helpref{wxMemoryDC}{wxmemorydc} for an example of drawing onto a bitmap.
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The following shows the conditional compilation required to load a
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bitmap in X and in Windows 3. The alternative is to use the string
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version of the bitmap constructor, which loads a file under X and a
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resource under Windows 3, but has the disadvantage of requiring the
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X icon file to be available at run-time.
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\begin{verbatim}
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#ifdef wx_x
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#include "aiai.xbm"
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#endif
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#ifdef wx_msw
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wxIcon *icon = new wxBitmap("aiai");
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#endif
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#ifdef wx_x
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wxIcon *icon = new wxBitmap(aiai_bits, aiai_width, aiai_height);
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#endif
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\end{verbatim}
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\subsection{Loading bitmaps: further information}
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There is provision for a number of bitmap
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formats via the standard wxBitmap class. These facilities can
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be enabled or disabled using settings in wx\_setup.h.
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XPM colour pixmaps may be loaded and saved under Windows and X, with
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some restrictions imposed by the lack of colourmap facility when
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using XPM files. The user may elect to use XPM files as a cross-platform
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stabdard, or translate between XPM and BMP files using a suitable
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utility.
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Also, under Windows, DIBs (device independent bitmaps with extension BMP)
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may be dynamically loaded and saved. Under X, GIF and BMP files may be
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loaded but not saved.
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\subsection{Bitmap format handlers}
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To provide extensibility, the functionality for loading and saving bitmap formats
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is not implemented in the wxBitmap class, but in a number of handler classes,
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derived from wxBitmapHandler. There is a static list of handlers which wxBitmap
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examines when a file load/save operation is requested. Some handlers are provided as standard, but if you
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have special requirements, you may wish to initialise the wxBitmap class with
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some extra handlers which you write yourself or receive from a third party.
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To add a handler object to wxBitmap, your application needs to include the header which implements it, and
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then call the static function \helpref{wxBitmap::AddHandler}{wxbitmapaddhandler}. For example:
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{\small
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\begin{verbatim}
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#include "JPEGBitmapHandler.h"
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...
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// Initialisation
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wxBitmap::AddHandler(new wxJPEGBitmapHandler);
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...
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\end{verbatim}
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}
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Assuming wxJPEGBitmapHandler has been written correctly, you should now be able to load and save JPEG files
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using the usual wxBitmap API.
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To see how bitmap handlers are implemented, please look at the files {\tt bitmap.h} and {\tt bitmap.cpp}.
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\subsection{wxIcon overview}\label{wxiconoverview}
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TODO.
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