e80658dacc
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@8997 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
63 lines
2.4 KiB
TeX
63 lines
2.4 KiB
TeX
\chapter{Images and bitmaps}\label{chapimages}
|
|
\pagenumbering{arabic}%
|
|
\setheader{{\it CHAPTER \thechapter: IMAGES AND BITMAPS}}{}{}{}{}{{\it CHAPTER \thechapter: IMAGES AND BITMAPS}}%
|
|
\setfooter{\thepage}{}{}{}{}{\thepage}%
|
|
|
|
\section{The basics of images and bitmaps}
|
|
|
|
Both wxImage and wxBitmap represent what would commonly be referred as
|
|
a photo with a given number of pixels - in contrast to a drawing consisting
|
|
of a collection of lines, curves, circles, squares etc.
|
|
|
|
The difference between a wxImage and a wxBitmap is that wxImage is a
|
|
platform and screen independent representation of an image - every
|
|
pixel is always represented by three bytes, one for red, one for green
|
|
and one for blue, thus yielding the classical RGB acronym. Due to the
|
|
simplicity of wxImage, you will do all kinds of image manipulation
|
|
with this class, this includes loading images in various formats
|
|
such as GIF, TIFF or JPEG (these and some more are supported by wxWindows
|
|
without further work), analyizing the image in terms of colour usage etc
|
|
and applying filters to the image for higher-level manipulation, such
|
|
as blurring, sharpening etc.
|
|
|
|
The problem with wxImage is that you cannot draw it, i.e. its destiny
|
|
is to live its shadow life in memory, without ever being seen by man.
|
|
If you ever want to draw an image to screen, you have to convert it
|
|
to a wxBitmap first, typically, this will look like this:
|
|
|
|
\begin{verbatim}
|
|
wxImage image( 200, 200 );
|
|
wxBitmap bitmap( image.ConvertToBitmap() );
|
|
|
|
wxClientDC dc( this )
|
|
dc.DrawBitmap( bitmap );
|
|
\end{verbatim}
|
|
|
|
Note, that such as image conversion is an extremely expensive operation
|
|
and you are very well advised to avoid having to call this routine
|
|
more than absolutely required. In practice, you should not do this
|
|
in a paint event handler, for instance.
|
|
|
|
There is one more thing you can do with a wxBitmap: you can draw into
|
|
it like you would do with a window. All you need to do is set up a
|
|
proper device context (DC) for it and ensure that you clean up the
|
|
DC correctly afterwards:
|
|
|
|
\begin{verbatim}
|
|
wxBitmap bitmap( 200, 200 );
|
|
|
|
wxMemoryDC dc;
|
|
dc.SelectObject( bitmap );
|
|
|
|
dc.SetPen( *wxBLACK_PEN );
|
|
dc.DrawLine( 0, 0, 199, 199 );
|
|
|
|
dc.SelectObject( wxNullBitmap );
|
|
\end{verbatim}
|
|
|
|
\section{wxImage built-in features}
|
|
|
|
You can save it, load it, get access to it, assign it a mask colour,
|
|
turn it around, mirror it.
|
|
|