184 lines
6.7 KiB
C
184 lines
6.7 KiB
C
/////////////////////////////////////////////////////////////////////////////
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// Name: bitmap.h
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// Purpose: topic overview
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// Author: wxWidgets team
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// Licence: wxWindows licence
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/////////////////////////////////////////////////////////////////////////////
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/**
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@page overview_bitmap Bitmaps and Icons
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@tableofcontents
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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 wxBitmap
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object from an existing file are catered for, and this is an occasion where
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conditional compilation will sometimes be required.
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A bitmap created dynamically or loaded from a file can be selected into a
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memory device context (instance of wxMemoryDC). This enables the bitmap to be
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copied to a window or memory device context using wxDC::Blit(), or to be used
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as a drawing surface.
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See wxMemoryDC for an example of drawing onto a bitmap.
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All wxWidgets platforms support XPMs for small bitmaps and icons. You may
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include the XPM inline as below, since it's C code, or you can load it at
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run-time.
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@code
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#include "sample.xpm"
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@endcode
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Sometimes you wish to use a .ico resource on Windows, and XPMs on other
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platforms (for example to take advantage of Windows' support for multiple icon
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resolutions).
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A macro, wxICON(), is available which creates an icon using an XPM on the
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appropriate platform, or an icon resource on Windows:
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@code
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wxIcon icon(wxICON(sample));
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// The above line is equivalent to this:
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#if defined(__WXGTK__) || defined(__WXMOTIF__)
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wxIcon icon(sample_xpm);
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#endif
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#if defined(__WXMSW__)
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wxIcon icon("sample");
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#endif
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@endcode
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There is also a corresponding wxBITMAP() macro which allows to create the
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bitmaps in much the same way as wxICON() creates icons. It assumes that bitmaps
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live in resources under Windows or OS2 and XPM files under all other platforms
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(for XPMs, the corresponding file must be included before this macro is used,
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of course, and the name of the bitmap should be the same as the resource name
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under Windows with @c _xpm suffix). For example:
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@code
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// an easy and portable way to create a bitmap
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wxBitmap bmp(wxBITMAP(bmpname));
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// which is roughly equivalent to the following
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#if defined(__WXMSW__) || defined(__WXPM__)
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wxBitmap bmp("bmpname", wxBITMAP_TYPE_BMP_RESOURCE);
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#else // Unix
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wxBitmap bmp(bmpname_xpm, wxBITMAP_TYPE_XPM);
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#endif
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@endcode
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You should always use wxICON() and wxBITMAP() macros because they work for any
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platform (unlike the code above which doesn't deal with wxMac, wxX11, ...) and
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are shorter and more clear than versions with many @ifdef_ blocks.
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Alternatively, you could use the same XPMs on all platforms and avoid dealing
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with Windows resource files.
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If you'd like to embed bitmaps with alpha transparency in your program, neither
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XPM nor BMP formats are appropriate as they don't have support for alpha and
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another format, typically PNG, should be used. wxWidgets provides a similar
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helper for PNG bitmaps called wxBITMAP_PNG() that can be used to either load
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PNG files embedded in resources (meaning either Windows resource section of the
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executable file or OS X "Resource" subdirectory of the application bundle) or
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arrays containing PNG data included into the program code itself.
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@see @ref group_class_gdi
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@section overview_bitmap_supportedformats Supported Bitmap File Formats
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The following lists the formats handled on different platforms. Note that
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missing or partially-implemented formats are automatically supplemented by
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using wxImage to load the data, and then converting it to wxBitmap form. Note
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that using wxImage is the preferred way to load images in wxWidgets, with the
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exception of resources (XPM-files or native Windows resources).
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Writing an image format handler for wxImage is also far easier than writing one
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for wxBitmap, because wxImage has exactly one format on all platforms whereas
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wxBitmap can store pixel data very differently, depending on colour depths and
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platform.
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@subsection overview_bitmap_supportedformats_bmp wxBitmap
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Under Windows, wxBitmap may load the following formats:
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@li Windows bitmap resource (wxBITMAP_TYPE_BMP_RESOURCE)
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@li Windows bitmap file (wxBITMAP_TYPE_BMP)
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@li XPM data and file (wxBITMAP_TYPE_XPM)
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@li All formats that are supported by the wxImage class.
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Under wxGTK, wxBitmap may load the following formats:
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@li XPM data and file (wxBITMAP_TYPE_XPM)
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@li All formats that are supported by the wxImage class.
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Under wxMotif and wxX11, wxBitmap may load the following formats:
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@li XBM data and file (wxBITMAP_TYPE_XBM)
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@li XPM data and file (wxBITMAP_TYPE_XPM)
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@li All formats that are supported by the wxImage class.
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@subsection overview_bitmap_supportedformats_icon wxIcon
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Under Windows, wxIcon may load the following formats:
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@li Windows icon resource (wxBITMAP_TYPE_ICO_RESOURCE)
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@li Windows icon file (wxBITMAP_TYPE_ICO)
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@li XPM data and file (wxBITMAP_TYPE_XPM)
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Under wxGTK, wxIcon may load the following formats:
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@li XPM data and file (wxBITMAP_TYPE_XPM)
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@li All formats that are supported by the wxImage class.
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Under wxMotif and wxX11, wxIcon may load the following formats:
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@li XBM data and file (wxBITMAP_TYPE_XBM)
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@li XPM data and file (wxBITMAP_TYPE_XPM)
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@li All formats that are supported by the wxImage class.
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@subsection overview_bitmap_supportedformats_cursor wxCursor
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Under Windows, wxCursor may load the following formats:
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@li Windows cursor resource (wxBITMAP_TYPE_CUR_RESOURCE)
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@li Windows cursor file (wxBITMAP_TYPE_CUR)
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@li Windows icon file (wxBITMAP_TYPE_ICO)
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@li Windows bitmap file (wxBITMAP_TYPE_BMP)
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Under wxGTK, wxCursor may load the following formats (in addition to stock
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cursors):
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@li None (stock cursors only).
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Under wxMotif and wxX11, wxCursor may load the following formats:
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@li XBM data and file (wxBITMAP_TYPE_XBM)
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@section overview_bitmap_handlers Bitmap Format Handlers
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To provide extensibility, the functionality for loading and saving bitmap
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formats is not implemented in the wxBitmap class, but in a number of handler
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classes, derived from wxBitmapHandler. There is a static list of handlers which
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wxBitmap examines when a file load/save operation is requested.
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Some handlers are provided as standard, but if you have special requirements,
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you may wish to initialise the wxBitmap class with some extra handlers which
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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
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header which implements it, and then call the static function
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wxBitmap::AddHandler().
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@note Bitmap handlers are not implemented on all platforms, and new ones rarely
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need to be implemented since wxImage can be used for loading most formats, as
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noted earlier.
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*/
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