qpixmap.3qt

Trolltech公司发布的基于C++图形开发环境

'\" t
.TH QPixmap 3qt "21 January 2005" "Trolltech AS" \" -*- nroff -*-
.\" Copyright 1992-2001 Trolltech AS.  All rights reserved.  See the
.\" license file included in the distribution for a complete license
.\" statement.
.\"
.ad l
.nh
.SH NAME
QPixmap \- Off-screen, pixel-based paint device
.SH SYNOPSIS
\fC#include <qpixmap.h>\fR
.PP
Inherits QPaintDevice and Qt.
.PP
Inherited by QBitmap and QCanvasPixmap.
.PP
.SS "Public Members"
.in +1c
.ti -1c
.BI "enum \fBColorMode\fR { Auto, Color, Mono }"
.br
.ti -1c
.BI "enum \fBOptimization\fR { DefaultOptim, NoOptim, MemoryOptim = NoOptim, NormalOptim, BestOptim }"
.br
.ti -1c
.BI "\fBQPixmap\fR ()"
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QImage & image )"
.br
.ti -1c
.BI "\fBQPixmap\fR ( int w, int h, int depth = -1, Optimization optimization = DefaultOptim )"
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QSize & size, int depth = -1, Optimization optimization = DefaultOptim )"
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QString & fileName, const char * format = 0, ColorMode mode = Auto )"
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QString & fileName, const char * format, int conversion_flags )"
.br
.ti -1c
.BI "\fBQPixmap\fR ( const char * xpm[] )"
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QByteArray & img_data )"
.br
.ti -1c
.BI "\fBQPixmap\fR ( const QPixmap & pixmap )"
.br
.ti -1c
.BI "\fB~QPixmap\fR ()"
.br
.ti -1c
.BI "QPixmap & \fBoperator=\fR ( const QPixmap & pixmap )"
.br
.ti -1c
.BI "QPixmap & \fBoperator=\fR ( const QImage & image )"
.br
.ti -1c
.BI "bool \fBisNull\fR () const"
.br
.ti -1c
.BI "int \fBwidth\fR () const"
.br
.ti -1c
.BI "int \fBheight\fR () const"
.br
.ti -1c
.BI "QSize \fBsize\fR () const"
.br
.ti -1c
.BI "QRect \fBrect\fR () const"
.br
.ti -1c
.BI "int \fBdepth\fR () const"
.br
.ti -1c
.BI "void \fBfill\fR ( const QColor & fillColor = Qt::white )"
.br
.ti -1c
.BI "void \fBfill\fR ( const QWidget * widget, int xofs, int yofs )"
.br
.ti -1c
.BI "void \fBfill\fR ( const QWidget * widget, const QPoint & ofs )"
.br
.ti -1c
.BI "void \fBresize\fR ( int w, int h )"
.br
.ti -1c
.BI "void \fBresize\fR ( const QSize & size )"
.br
.ti -1c
.BI "const QBitmap * \fBmask\fR () const"
.br
.ti -1c
.BI "void \fBsetMask\fR ( const QBitmap & newmask )"
.br
.ti -1c
.BI "bool \fBselfMask\fR () const"
.br
.ti -1c
.BI "bool \fBhasAlpha\fR () const"
.br
.ti -1c
.BI "bool \fBhasAlphaChannel\fR () const"
.br
.ti -1c
.BI "QBitmap \fBcreateHeuristicMask\fR ( bool clipTight = TRUE ) const"
.br
.ti -1c
.BI "QPixmap \fBxForm\fR ( const QWMatrix & matrix ) const"
.br
.ti -1c
.BI "QImage \fBconvertToImage\fR () const"
.br
.ti -1c
.BI "bool \fBconvertFromImage\fR ( const QImage & image, ColorMode mode = Auto )"
.br
.ti -1c
.BI "bool \fBconvertFromImage\fR ( const QImage & img, int conversion_flags )"
.br
.ti -1c
.BI "bool \fBload\fR ( const QString & fileName, const char * format = 0, ColorMode mode = Auto )"
.br
.ti -1c
.BI "bool \fBload\fR ( const QString & fileName, const char * format, int conversion_flags )"
.br
.ti -1c
.BI "bool \fBloadFromData\fR ( const uchar * buf, uint len, const char * format = 0, ColorMode mode = Auto )"
.br
.ti -1c
.BI "bool \fBloadFromData\fR ( const uchar * buf, uint len, const char * format, int conversion_flags )"
.br
.ti -1c
.BI "bool \fBloadFromData\fR ( const QByteArray & buf, const char * format = 0, int conversion_flags = 0 )"
.br
.ti -1c
.BI "bool \fBsave\fR ( const QString & fileName, const char * format, int quality = -1 ) const"
.br
.ti -1c
.BI "bool \fBsave\fR ( QIODevice * device, const char * format, int quality = -1 ) const"
.br
.ti -1c
.BI "int \fBserialNumber\fR () const"
.br
.ti -1c
.BI "Optimization \fBoptimization\fR () const"
.br
.ti -1c
.BI "void \fBsetOptimization\fR ( Optimization optimization )"
.br
.ti -1c
.BI "virtual void \fBdetach\fR ()"
.br
.ti -1c
.BI "bool \fBisQBitmap\fR () const"
.br
.in -1c
.SS "Static Public Members"
.in +1c
.ti -1c
.BI "int \fBdefaultDepth\fR ()"
.br
.ti -1c
.BI "QPixmap \fBfromMimeSource\fR ( const QString & abs_name )"
.br
.ti -1c
.BI "QPixmap \fBgrabWindow\fR ( WId window, int x = 0, int y = 0, int w = -1, int h = -1 )"
.br
.ti -1c
.BI "QPixmap \fBgrabWidget\fR ( QWidget * widget, int x = 0, int y = 0, int w = -1, int h = -1 )"
.br
.ti -1c
.BI "QWMatrix \fBtrueMatrix\fR ( const QWMatrix & matrix, int w, int h )"
.br
.ti -1c
.BI "const char * \fBimageFormat\fR ( const QString & fileName )"
.br
.ti -1c
.BI "Optimization \fBdefaultOptimization\fR ()"
.br
.ti -1c
.BI "void \fBsetDefaultOptimization\fR ( Optimization optimization )"
.br
.in -1c
.SS "Protected Members"
.in +1c
.ti -1c
.BI "\fBQPixmap\fR ( int w, int h, const uchar * bits, bool isXbitmap )"
.br
.ti -1c
.BI "virtual int \fBmetric\fR ( int m ) const"
.br
.in -1c
.SH RELATED FUNCTION DOCUMENTATION
.in +1c
.ti -1c
.BI "QDataStream & \fBoperator<<\fR ( QDataStream & s, const QPixmap & pixmap )"
.br
.ti -1c
.BI "QDataStream & \fBoperator>>\fR ( QDataStream & s, QPixmap & pixmap )"
.br
.ti -1c
.BI "void \fBcopyBlt\fR ( QPixmap * dst, int dx, int dy, const QPixmap * src, int sx, int sy, int sw, int sh )"
.br
.in -1c
.SH DESCRIPTION
The QPixmap class is an off-screen, pixel-based paint device.
.PP
QPixmap is one of the two classes Qt provides for dealing with images; the other is QImage. QPixmap is designed and optimized for drawing; QImage is designed and optimized for I/O and for direct pixel access/manipulation. There are (slow) functions to convert between QImage and QPixmap: convertToImage() and convertFromImage().
.PP
One common use of the QPixmap class is to enable smooth updating of widgets. Whenever something complex needs to be drawn, you can use a pixmap to obtain flicker-free drawing, like this:
.PP
<ol type=1>
.IP 1
Create a pixmap with the same size as the widget.
.IP 2
Fill the pixmap with the widget background color.
.IP 3
Paint the pixmap.
.IP 4
bitBlt() the pixmap contents onto the widget.
.PP
Pixel data in a pixmap is internal and is managed by the underlying window system. Pixels can be accessed only through QPainter functions, through bitBlt(), and by converting the QPixmap to a QImage.
.PP
You can easily display a QPixmap on the screen using QLabel::setPixmap(). For example, all the QButton subclasses support pixmap use.
.PP
The QPixmap class uses copy-on-write, so it is practical to pass QPixmap objects by value.
.PP
You can retrieve the width(), height(), depth() and size() of a pixmap. The enclosing rectangle is given by rect(). Pixmaps can be filled with fill() and resized with resize(). You can create and set a mask with createHeuristicMask() and setMask(). Use selfMask() to see if the pixmap is identical to its mask.
.PP
In addition to loading a pixmap from file using load() you can also loadFromData(). You can control optimization with setOptimization() and obtain a transformed version of the pixmap using xForm()
.PP
Note regarding Windows 95 and 98: on Windows 9x the system crashes if you create more than about 1000 pixmaps, independent of the size of the pixmaps or installed RAM. Windows NT-systems (including 2000, XP and following versions) do not have the same limitation, but depending on the graphics equipment the system will fail to allocate pixmap objects at some point (due to system running out of GDI resources).
.PP
Qt tries to work around the resource limitation. If you set the pixmap optimization to QPixmap::MemoryOptim and the width of your pixmap is less than or equal to 128 pixels, Qt stores the pixmap in a way that is very memory-efficient when there are many pixmaps.
.PP
If your application uses dozens or hundreds of pixmaps (for example on tool bar buttons and in popup menus), and you plan to run it on Windows 95 or Windows 98, we recommend using code like this:
.PP
.nf
.br
        QPixmap::setDefaultOptimization( QPixmap::MemoryOptim );
.br
        while ( ... ) {
.br
            // load tool bar pixmaps etc.
.br
            QPixmap *pixmap = new QPixmap(fileName);
.br
        }
.br
        QPixmap::setDefaultOptimization( QPixmap::NormalOptim );
.br
.fi
.PP
In general it is recommended to make as much use of QPixmap's implicit sharing and the QPixmapCache as possible.
.PP
See also QBitmap, QImage, QImageIO, Shared Classes, Graphics Classes, Image Processing Classes, and Implicitly and Explicitly Shared Classes.
.SS "Member Type Documentation"
.SH "QPixmap::ColorMode"