QImage(3qt)QImage(3qt)NAME
QImage - Hardware-independent pixmap representation with direct access
to the pixel data
SYNOPSIS
#include <qimage.h>
Public Members
enum Endian { IgnoreEndian, BigEndian, LittleEndian }
QImage ()
QImage ( int w, int h, int depth, int numColors = 0, Endian bitOrder =
IgnoreEndian )
QImage ( const QSize & size, int depth, int numColors = 0, Endian
bitOrder = IgnoreEndian )
QImage ( const QString & fileName, const char * format = 0 )
QImage ( const char * const xpm[] )
QImage ( const QByteArray & array )
QImage ( uchar * yourdata, int w, int h, int depth, QRgb * colortable,
int numColors, Endian bitOrder )
QImage ( uchar * yourdata, int w, int h, int depth, int bpl, QRgb *
colortable, int numColors, Endian bitOrder )
QImage ( const QImage & image )
~QImage ()
QImage & operator= ( const QImage & image )
QImage & operator= ( const QPixmap & pixmap )
bool operator== ( const QImage & i ) const
bool operator!= ( const QImage & i ) const
void detach ()
QImage copy () const
QImage copy ( int x, int y, int w, int h, int conversion_flags = 0 )
const
QImage copy ( const QRect & r ) const
bool isNull () const
int width () const
int height () const
QSize size () const
QRect rect () const
int depth () const
int numColors () const
Endian bitOrder () const
QRgb color ( int i ) const
void setColor ( int i, QRgb c )
void setNumColors ( int numColors )
bool hasAlphaBuffer () const
void setAlphaBuffer ( bool enable )
bool allGray () const
bool isGrayscale () const
uchar * bits () const
uchar * scanLine ( int i ) const
uchar ** jumpTable () const
QRgb * colorTable () const
int numBytes () const
int bytesPerLine () const
bool create ( int width, int height, int depth, int numColors = 0,
Endian bitOrder = IgnoreEndian )
bool create ( const QSize &, int depth, int numColors = 0, Endian
bitOrder = IgnoreEndian )
void reset ()
void fill ( uint pixel )
void invertPixels ( bool invertAlpha = TRUE )
QImage convertDepth ( int depth ) const
QImage convertDepthWithPalette ( int d, QRgb * palette, int
palette_count, int conversion_flags = 0 ) const
QImage convertDepth ( int depth, int conversion_flags ) const
QImage convertBitOrder ( Endian bitOrder ) const
enum ScaleMode { ScaleFree, ScaleMin, ScaleMax }
QImage smoothScale ( int w, int h, ScaleMode mode = ScaleFree ) const
QImage smoothScale ( const QSize & s, ScaleMode mode = ScaleFree )
const
QImage scale ( int w, int h, ScaleMode mode = ScaleFree ) const
QImage scale ( const QSize & s, ScaleMode mode = ScaleFree ) const
QImage scaleWidth ( int w ) const
QImage scaleHeight ( int h ) const
QImage xForm ( const QWMatrix & matrix ) const
QImage createAlphaMask ( int conversion_flags = 0 ) const
QImage createHeuristicMask ( bool clipTight = TRUE ) const
QImage mirror () const
QImage mirror ( bool horizontal, bool vertical ) const
QImage swapRGB () const
bool load ( const QString & fileName, const char * format = 0 )
bool loadFromData ( const uchar * buf, uint len, const char * format =
0 )
bool loadFromData ( QByteArray buf, const char * format = 0 )
bool save ( const QString & fileName, const char * format, int quality
= -1 ) const
bool save ( QIODevice * device, const char * format, int quality = -1 )
const
bool valid ( int x, int y ) const
int pixelIndex ( int x, int y ) const
QRgb pixel ( int x, int y ) const
void setPixel ( int x, int y, uint index_or_rgb )
int dotsPerMeterX () const
int dotsPerMeterY () const
void setDotsPerMeterX ( int x )
void setDotsPerMeterY ( int y )
QPoint offset () const
void setOffset ( const QPoint & p )
QValueList<QImageTextKeyLang> textList () const
QStringList textLanguages () const
QStringList textKeys () const
QString text ( const char * key, const char * lang = 0 ) const
QString text ( const QImageTextKeyLang & kl ) const
void setText ( const char * key, const char * lang, const QString & s )
Static Public Members
QImage fromMimeSource ( const QString & abs_name )
Endian systemBitOrder ()
Endian systemByteOrder ()
const char * imageFormat ( const QString & fileName )
QStrList inputFormats ()
QStrList outputFormats ()
QStringList inputFormatList ()
QStringList outputFormatList ()
RELATED FUNCTION DOCUMENTATION
QDataStream & operator<< ( QDataStream & s, const QImage & image )
QDataStream & operator>> ( QDataStream & s, QImage & image )
void bitBlt ( QImage * dst, int dx, int dy, const QImage * src, int sx,
int sy, int sw, int sh, int conversion_flags )
DESCRIPTION
The QImage class provides a hardware-independent pixmap representation
with direct access to the pixel data.
It is one of the two classes Qt provides for dealing with images, the
other being QPixmap. QImage is designed and optimized for I/O and for
direct pixel access/manipulation. QPixmap is designed and optimized for
drawing. There are (slow) functions to convert between QImage and
QPixmap: QPixmap::convertToImage() and QPixmap::convertFromImage().
An image has the parameters width, height and depth (bits per pixel,
bpp), a color table and the actual pixels. QImage supports 1-bpp, 8-bpp
and 32-bpp image data. 1-bpp and 8-bpp images use a color lookup table;
the pixel value is a color table index.
32-bpp images encode an RGB value in 24 bits and ignore the color
table. The most significant byte is used for the alpha buffer.
An entry in the color table is an RGB triplet encoded as a uint. Use
the qRed(), qGreen() and qBlue() functions (qcolor.h) to access the
components, and qRgb to make an RGB triplet (see the QColor class
documentation).
1-bpp (monochrome) images have a color table with a most two colors.
There are two different formats: big endian (MSB first) or little
endian (LSB first) bit order. To access a single bit you will must do
some bit shifts:
QImage image;
// sets bit at (x,y) to 1
if ( image.bitOrder() == QImage::LittleEndian )
*(image.scanLine(y) + (x >> 3)) |= 1 << (x & 7);
else
*(image.scanLine(y) + (x >> 3)) |= 1 << (7 - (x & 7));
If this looks complicated, it might be a good idea to convert the 1-bpp
image to an 8-bpp image using convertDepth().
8-bpp images are much easier to work with than 1-bpp images because
they have a single byte per pixel:
QImage image;
// set entry 19 in the color table to yellow
image.setColor( 19, qRgb(255,255,0) );
// set 8 bit pixel at (x,y) to value yellow (in color table)
*(image.scanLine(y) + x) = 19;
32-bpp images ignore the color table; instead, each pixel contains the
RGB triplet. 24 bits contain the RGB value; the most significant byte
is reserved for the alpha buffer.
QImage image;
// sets 32 bit pixel at (x,y) to yellow.
uint *p = (uint *)image.scanLine(y) + x;
*p = qRgb(255,255,0);
On Qt/Embedded, scanlines are aligned to the pixel depth and may be
padded to any degree, while on all other platforms, the scanlines are
32-bit aligned for all depths. The constructor taking a uchar* argument
always expects 32-bit aligned data. On Qt/Embedded, an additional
constructor allows the number of bytes-per-line to be specified.
QImage supports a variety of methods for getting information about the
image, for example, colorTable(), allGray(), isGrayscale(), bitOrder(),
bytesPerLine(), depth(), dotsPerMeterX() and dotsPerMeterY(),
hasAlphaBuffer(), numBytes(), numColors(), and width() and height().
Pixel colors are retrieved with pixel() and set with setPixel().
QImage also supports a number of functions for creating a new image
that is a transformed version of the original. For example, copy(),
convertBitOrder(), convertDepth(), createAlphaMask(),
createHeuristicMask(), mirror(), scale(), smoothScale(), swapRGB() and
xForm(). There are also functions for changing attributes of an image
in-place, for example, setAlphaBuffer(), setColor(), setDotsPerMeterX()
and setDotsPerMeterY() and setNumColors().
Images can be loaded and saved in the supported formats. Images are
saved to a file with save(). Images are loaded from a file with load()
(or in the constructor) or from an array of data with loadFromData().
The lists of supported formats are available from inputFormatList() and
outputFormatList().
Strings of text may be added to images using setText().
The QImage class uses explicit sharing, similar to that used by
QMemArray.
New image formats can be added as plugins.
See also QImageIO, QPixmap, Shared Classes, Graphics Classes, Image
Processing Classes, and Implicitly and Explicitly Shared Classes.
Member Type Documentation
QImage::Endian
This enum type is used to describe the endianness of the CPU and
graphics hardware.
QImage::IgnoreEndian - Endianness does not matter. Useful for some
operations that are independent of endianness.
QImage::BigEndian - Network byte order, as on SPARC and Motorola CPUs.
QImage::LittleEndian - PC/Alpha byte order.
QImage::ScaleMode
The functions scale() and smoothScale() use different modes for scaling
the image. The purpose of these modes is to retain the ratio of the
image if this is required.
<center>
[Image Omitted]
</center>
QImage::ScaleFree - The image is scaled freely: the resulting image
fits exactly into the specified size; the ratio will not necessarily be
preserved.
QImage::ScaleMin - The ratio of the image is preserved and the
resulting image is guaranteed to fit into the specified size (it is as
large as possible within these constraints) - the image might be
smaller than the requested size.
QImage::ScaleMax - The ratio of the image is preserved and the
resulting image fills the whole specified rectangle (it is as small as
possible within these constraints) - the image might be larger than the
requested size.
MEMBER FUNCTION DOCUMENTATIONQImage::QImage ()
Constructs a null image.
See also isNull().
QImage::QImage ( int w, int h, int depth, int numColors = 0, Endian bitOrder =
IgnoreEndian )
Constructs an image with w width, h height, depth bits per pixel,
numColors colors and bit order bitOrder.
Using this constructor is the same as first constructing a null image
and then calling the create() function.
See also create().
QImage::QImage ( const QSize & size, int depth, int numColors = 0, Endian
bitOrder = IgnoreEndian )
Constructs an image with size size pixels, depth depth bits, numColors
and bitOrder endianness.
Using this constructor is the same as first constructing a null image
and then calling the create() function.
See also create().
QImage::QImage ( const QString & fileName, const char * format = 0 )
Constructs an image and tries to load the image from the file fileName.
If format is specified, the loader attempts to read the image using the
specified format. If format is not specified (which is the default),
the loader reads a few bytes from the header to guess the file format.
If the loading of the image failed, this object is a null image.
The QImageIO documentation lists the supported image formats and
explains how to add extra formats.
See also load(), isNull(), and QImageIO.
QImage::QImage ( const char * const xpm[] )
Constructs an image from xpm, which must be a valid XPM image.
Errors are silently ignored.
Note that it's possible to squeeze the XPM variable a little bit by
using an unusual declaration:
static const char * const start_xpm[]={
"16 15 8 1",
"a c #cec6bd",
....
The extra const makes the entire definition read-only, which is
slightly more efficient (e.g. when the code is in a shared library) and
ROMable when the application is to be stored in ROM.
QImage::QImage ( const QByteArray & array )
Constructs an image from the binary data array. It tries to guess the
file format.
If the loading of the image failed, this object is a null image.
See also loadFromData(), isNull(), and imageFormat().
QImage::QImage ( uchar * yourdata, int w, int h, int depth, QRgb * colortable,
int numColors, Endian bitOrder )
Constructs an image w pixels wide, h pixels high with a color depth of
depth, that uses an existing memory buffer, yourdata. The buffer must
remain valid throughout the life of the QImage. The image does not
delete the buffer at destruction.
If colortable is 0, a color table sufficient for numColors will be
allocated (and destructed later).
Note that yourdata must be 32-bit aligned.
The endianness is given in bitOrder.
QImage::QImage ( uchar * yourdata, int w, int h, int depth, int bpl, QRgb *
colortable, int numColors, Endian bitOrder )
Constructs an image that uses an existing memory buffer. The buffer
must remain valid for the life of the QImage. The image does not delete
the buffer at destruction. The buffer is passed as yourdata. The
image's width is w and its height is h. The color depth is depth. bpl
specifies the number of bytes per line.
If colortable is 0, a color table sufficient for numColors will be
allocated (and destructed later).
The endianness is specified by bitOrder.
Warning: This constructor is only available on Qt/Embedded.
QImage::QImage ( const QImage & image )
Constructs a shallow copy of image.
QImage::~QImage ()
Destroys the image and cleans up.
bool QImage::allGray () const
Returns TRUE if all the colors in the image are shades of gray (i.e.
their red, green and blue components are equal); otherwise returns
FALSE.
This function is slow for large 16-bit (Qt/Embedded only) and 32-bit
images.
See also isGrayscale().
Endian QImage::bitOrder () const
Returns the bit order for the image.
If it is a 1-bpp image, this function returns either QImage::BigEndian
or QImage::LittleEndian.
If it is not a 1-bpp image, this function returns QImage::IgnoreEndian.
See also depth().
uchar * QImage::bits () const
Returns a pointer to the first pixel data. This is equivalent to
scanLine(0).
See also numBytes(), scanLine(), and jumpTable().
Example: opengl/texture/gltexobj.cpp.
int QImage::bytesPerLine () const
Returns the number of bytes per image scanline. This is equivalent to
numBytes()/height().
See also numBytes() and scanLine().
QRgb QImage::color ( int i ) const
Returns the color in the color table at index i. The first color is at
index 0.
A color value is an RGB triplet. Use the qRed(), qGreen() and qBlue()
functions (defined in qcolor.h) to get the color value components.
See also setColor(), numColors(), and QColor.
Example: themes/wood.cpp.
QRgb * QImage::colorTable () const
Returns a pointer to the color table.
See also numColors().
QImage QImage::convertBitOrder ( Endian bitOrder ) const
Converts the bit order of the image to bitOrder and returns the
converted image. The original image is not changed.
Returns *this if the bitOrder is equal to the image bit order, or a
null image if this image cannot be converted.
See also bitOrder(), systemBitOrder(), and isNull().
QImage QImage::convertDepth ( int depth, int conversion_flags ) const
Converts the depth (bpp) of the image to depth and returns the
converted image. The original image is not changed.
The depth argument must be 1, 8, 16 (Qt/Embedded only) or 32.
Returns *this if depth is equal to the image depth, or a null image if
this image cannot be converted.
If the image needs to be modified to fit in a lower-resolution result
(e.g. converting from 32-bit to 8-bit), use the conversion_flags to
specify how you'd prefer this to happen.
See also Qt::ImageConversionFlags, depth(), and isNull().
QImage QImage::convertDepth ( int depth ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
QImage QImage::convertDepthWithPalette ( int d, QRgb * palette, int
palette_count, int conversion_flags = 0 ) const
Returns an image with depth d, using the palette_count colors pointed
to by palette. If d is 1 or 8, the returned image will have its color
table ordered the same as palette.
If the image needs to be modified to fit in a lower-resolution result
(e.g. converting from 32-bit to 8-bit), use the conversion_flags to
specify how you'd prefer this to happen.
Note: currently no closest-color search is made. If colors are found
that are not in the palette, the palette may not be used at all. This
result should not be considered valid because it may change in future
implementations.
Currently inefficient for non-32-bit images.
See also Qt::ImageConversionFlags.
QImage QImage::copy () const
Returns a deep copy of the image.
See also detach().
QImage QImage::copy ( int x, int y, int w, int h, int conversion_flags = 0 )
const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns a deep copy of a sub-area of the image.
The returned image is always w by h pixels in size, and is copied from
position x, y in this image. In areas beyond this image pixels are
filled with pixel 0.
If the image needs to be modified to fit in a lower-resolution result
(e.g. converting from 32-bit to 8-bit), use the conversion_flags to
specify how you'd prefer this to happen.
See also bitBlt() and Qt::ImageConversionFlags.
QImage QImage::copy ( const QRect & r ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns a deep copy of a sub-area of the image.
The returned image always has the size of the rectangle r. In areas
beyond this image pixels are filled with pixel 0.
bool QImage::create ( int width, int height, int depth, int numColors = 0,
Endian bitOrder = IgnoreEndian )
Sets the image width, height, depth, its number of colors (in
numColors), and bit order. Returns TRUE if successful, or FALSE if the
parameters are incorrect or if memory cannot be allocated.
The width and height is limited to 32767. depth must be 1, 8, or 32. If
depth is 1, bitOrder must be set to either QImage::LittleEndian or
QImage::BigEndian. For other depths bitOrder must be
QImage::IgnoreEndian.
This function allocates a color table and a buffer for the image data.
The image data is not initialized.
The image buffer is allocated as a single block that consists of a
table of scanline pointers (jumpTable()) and the image data (bits()).
See also fill(), width(), height(), depth(), numColors(), bitOrder(),
jumpTable(), scanLine(), bits(), bytesPerLine(), and numBytes().
bool QImage::create ( const QSize &, int depth, int numColors = 0, Endian
bitOrder = IgnoreEndian )
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
QImage QImage::createAlphaMask ( int conversion_flags = 0 ) const
Builds and returns a 1-bpp mask from the alpha buffer in this image.
Returns a null image if alpha buffer mode is disabled.
See QPixmap::convertFromImage() for a description of the
conversion_flags argument.
The returned image has little-endian bit order, which you can convert
to big-endianness using convertBitOrder().
See also createHeuristicMask(), hasAlphaBuffer(), and setAlphaBuffer().
QImage QImage::createHeuristicMask ( bool clipTight = TRUE ) const
Creates and returns a 1-bpp heuristic mask for this image. It works by
selecting a color from one of the corners, then chipping away pixels of
that color starting at all the edges.
The four corners vote for which color is to be masked away. In case of
a draw (this generally means that this function is not applicable to
the image), the result is arbitrary.
The returned image has little-endian bit order, which you can convert
to big-endianness using convertBitOrder().
If clipTight is TRUE the mask is just large enough to cover the pixels;
otherwise, the mask is larger than the data pixels.
This function disregards the alpha buffer.
See also createAlphaMask().
int QImage::depth () const
Returns the depth of the image.
The image depth is the number of bits used to encode a single pixel,
also called bits per pixel (bpp) or bit planes of an image.
The supported depths are 1, 8, 16 (Qt/Embedded only) and 32.
See also convertDepth().
void QImage::detach ()
Detaches from shared image data and makes sure that this image is the
only one referring to the data.
If multiple images share common data, this image makes a copy of the
data and detaches itself from the sharing mechanism. Nothing is done if
there is just a single reference.
See also copy().
Example: themes/wood.cpp.
int QImage::dotsPerMeterX () const
Returns the number of pixels that fit horizontally in a physical meter.
This and dotsPerMeterY() define the intended scale and aspect ratio of
the image.
See also setDotsPerMeterX().
int QImage::dotsPerMeterY () const
Returns the number of pixels that fit vertically in a physical meter.
This and dotsPerMeterX() define the intended scale and aspect ratio of
the image.
See also setDotsPerMeterY().
void QImage::fill ( uint pixel )
Fills the entire image with the pixel value pixel.
If the depth of this image is 1, only the lowest bit is used. If you
say fill(0), fill(2), etc., the image is filled with 0s. If you say
fill(1), fill(3), etc., the image is filled with 1s. If the depth is 8,
the lowest 8 bits are used.
If the depth is 32 and the image has no alpha buffer, the pixel value
is written to each pixel in the image. If the image has an alpha
buffer, only the 24 RGB bits are set and the upper 8 bits (alpha value)
are left unchanged.
Note: QImage::pixel() returns the color of the pixel at the given
coordinates; QColor::pixel() returns the pixel value of the underlying
window system (essentially an index value), so normally you will want
to use QImage::pixel() to use a color from an existing image or
QColor::rgb() to use a specific color.
See also invertPixels(), depth(), hasAlphaBuffer(), and create().
QImage QImage::fromMimeSource ( const QString & abs_name ) [static]
Convenience function. Gets the data associated with the absolute name
abs_name from the default mime source factory and decodes it to an
image.
See also QMimeSourceFactory, QImage::fromMimeSource(), and
QImageDrag::decode().
bool QImage::hasAlphaBuffer () const
Returns TRUE if alpha buffer mode is enabled; otherwise returns FALSE.
See also setAlphaBuffer().
int QImage::height () const
Returns the height of the image.
See also width(), size(), and rect().
Examples:
const char * QImage::imageFormat ( const QString & fileName ) [static]
Returns a string that specifies the image format of the file fileName,
or 0 if the file cannot be read or if the format is not recognized.
The QImageIO documentation lists the guaranteed supported image
formats, or use QImage::inputFormats() and QImage::outputFormats() to
get lists that include the installed formats.
See also load() and save().
QStringList QImage::inputFormatList () [static]
Returns a list of image formats that are supported for image input.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = myImage.inputFormatList();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See also outputFormatList(), inputFormats(), and QImageIO.
Example: showimg/showimg.cpp.
QStrList QImage::inputFormats () [static]
Returns a list of image formats that are supported for image input.
See also outputFormats(), inputFormatList(), and QImageIO.
void QImage::invertPixels ( bool invertAlpha = TRUE )
Inverts all pixel values in the image.
If the depth is 32: if invertAlpha is TRUE, the alpha bits are also
inverted, otherwise they are left unchanged.
If the depth is not 32, the argument invertAlpha has no meaning.
Note that inverting an 8-bit image means to replace all pixels using
color index i with a pixel using color index 255 minus i. Similarly for
a 1-bit image. The color table is not changed.
See also fill(), depth(), and hasAlphaBuffer().
bool QImage::isGrayscale () const
For 16-bit (Qt/Embedded only) and 32-bit images, this function is
equivalent to allGray().
For 8-bpp images, this function returns TRUE if color(i) is QRgb(i,i,i)
for all indices of the color table; otherwise returns FALSE.
See also allGray() and depth().
bool QImage::isNull () const
Returns TRUE if it is a null image; otherwise returns FALSE.
A null image has all parameters set to zero and no allocated data.
Example: showimg/showimg.cpp.
uchar ** QImage::jumpTable () const
Returns a pointer to the scanline pointer table.
This is the beginning of the data block for the image.
See also bits() and scanLine().
bool QImage::load ( const QString & fileName, const char * format = 0 )
Loads an image from the file fileName. Returns TRUE if the image was
successfully loaded; otherwise returns FALSE.
If format is specified, the loader attempts to read the image using the
specified format. If format is not specified (which is the default),
the loader reads a few bytes from the header to guess the file format.
The QImageIO documentation lists the supported image formats and
explains how to add extra formats.
See also loadFromData(), save(), imageFormat(), QPixmap::load(), and
QImageIO.
bool QImage::loadFromData ( const uchar * buf, uint len, const char * format =
0 )
Loads an image from the first len bytes of binary data in buf. Returns
TRUE if the image was successfully loaded; otherwise returns FALSE.
If format is specified, the loader attempts to read the image using the
specified format. If format is not specified (which is the default),
the loader reads a few bytes from the header to guess the file format.
The QImageIO documentation lists the supported image formats and
explains how to add extra formats.
See also load(), save(), imageFormat(), QPixmap::loadFromData(), and
QImageIO.
bool QImage::loadFromData ( QByteArray buf, const char * format = 0 )
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Loads an image from the QByteArray buf.
QImage QImage::mirror () const
Returns a QImage which is a vertically mirrored copy of this image. The
original QImage is not changed.
QImage QImage::mirror ( bool horizontal, bool vertical ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns a mirror of the image, mirrored in the horizontal and/or the
vertical direction depending on whether horizontal and vertical are set
to TRUE or FALSE. The original image is not changed.
See also smoothScale().
int QImage::numBytes () const
Returns the number of bytes occupied by the image data.
See also bytesPerLine() and bits().
int QImage::numColors () const
Returns the size of the color table for the image.
Notice that numColors() returns 0 for 16-bpp (Qt/Embedded only) and
32-bpp images because these images do not use color tables, but instead
encode pixel values as RGB triplets.
See also setNumColors() and colorTable().
Example: themes/wood.cpp.
QPoint QImage::offset () const
Returns the number of pixels by which the image is intended to be
offset by when positioning relative to other images.
bool QImage::operator!= ( const QImage & i ) const
Returns TRUE if this image and image i have different contents;
otherwise returns FALSE. The comparison can be slow, unless there is
some obvious difference, such as different widths, in which case the
function will return quickly.
See also operator=().
QImage & QImage::operator= ( const QImage & image )
Assigns a shallow copy of image to this image and returns a reference
to this image.
See also copy().
QImage & QImage::operator= ( const QPixmap & pixmap )
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Sets the image bits to the pixmap contents and returns a reference to
the image.
If the image shares data with other images, it will first dereference
the shared data.
Makes a call to QPixmap::convertToImage().
bool QImage::operator== ( const QImage & i ) const
Returns TRUE if this image and image i have the same contents;
otherwise returns FALSE. The comparison can be slow, unless there is
some obvious difference, such as different widths, in which case the
function will return quickly.
See also operator=().
QStringList QImage::outputFormatList () [static]
Returns a list of image formats that are supported for image output.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = myImage.outputFormatList();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See also inputFormatList(), outputFormats(), and QImageIO.
QStrList QImage::outputFormats () [static]
Returns a list of image formats that are supported for image output.
See also inputFormats(), outputFormatList(), and QImageIO.
Example: showimg/showimg.cpp.
QRgb QImage::pixel ( int x, int y ) const
Returns the color of the pixel at the coordinates (x, y).
If (x, y) is not on the image, the results are undefined.
See also setPixel(), qRed(), qGreen(), qBlue(), and valid().
Examples:
int QImage::pixelIndex ( int x, int y ) const
Returns the pixel index at the given coordinates.
If (x, y) is not valid, or if the image is not a paletted image
(depth() > 8), the results are undefined.
See also valid() and depth().
QRect QImage::rect () const
Returns the enclosing rectangle (0, 0, width(), height()) of the image.
See also width(), height(), and size().
void QImage::reset ()
Resets all image parameters and deallocates the image data.
bool QImage::save ( const QString & fileName, const char * format, int quality
= -1 ) const
Saves the image to the file fileName, using the image file format
format and a quality factor of quality. quality must be in the range
0..100 or -1. Specify 0 to obtain small compressed files, 100 for large
uncompressed files, and -1 (the default) to use the default settings.
Returns TRUE if the image was successfully saved; otherwise returns
FALSE.
See also load(), loadFromData(), imageFormat(), QPixmap::save(), and
QImageIO.
bool QImage::save ( QIODevice * device, const char * format, int quality = -1
) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
This function writes a QImage to the QIODevice, device. This can be
used, for example, to save an image directly into a QByteArray:
QImage image;
QByteArray ba;
QBuffer buffer( ba );
buffer.open( IO_WriteOnly );
image.save( &buffer, "PNG" ); // writes image into ba in PNG format
QImage QImage::scale ( int w, int h, ScaleMode mode = ScaleFree ) const
Returns a copy of the image scaled to a rectangle of width w and height
h according to the ScaleMode mode.
If mode is ScaleFree, the image is scaled to (w, h).
If mode is ScaleMin, the image is scaled to a rectangle as large as
possible inside (w, h), preserving the aspect ratio.
If mode is ScaleMax, the image is scaled to a rectangle as small as
possible outside (w, h), preserving the aspect ratio.
If either the width w or the height h is 0 or negative, this function
returns a null image.
This function uses a simple, fast algorithm. If you need better
quality, use smoothScale() instead.
See also scaleWidth(), scaleHeight(), smoothScale(), and xForm().
QImage QImage::scale ( const QSize & s, ScaleMode mode = ScaleFree ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
The requested size of the image is s.
QImage QImage::scaleHeight ( int h ) const
Returns a scaled copy of the image. The returned image has a height of
h pixels. This function automatically calculates the width of the image
so that the ratio of the image is preserved.
If h is 0 or negative a null image is returned.
See also scale(), scaleWidth(), smoothScale(), and xForm().
Example: table/small-table-demo/main.cpp.
QImage QImage::scaleWidth ( int w ) const
Returns a scaled copy of the image. The returned image has a width of w
pixels. This function automatically calculates the height of the image
so that the ratio of the image is preserved.
If w is 0 or negative a null image is returned.
See also scale(), scaleHeight(), smoothScale(), and xForm().
uchar * QImage::scanLine ( int i ) const
Returns a pointer to the pixel data at the scanline with index i. The
first scanline is at index 0.
The scanline data is aligned on a 32-bit boundary.
Warning: If you are accessing 32-bpp image data, cast the returned
pointer to QRgb* (QRgb has a 32-bit size) and use it to read/write the
pixel value. You cannot use the uchar* pointer directly, because the
pixel format depends on the byte order on the underlying platform.
Hint: use qRed(), qGreen() and qBlue(), etc. (qcolor.h) to access the
pixels.
Warning: If you are accessing 16-bpp image data, you must handle
endianness yourself. (Qt/Embedded only)
See also bytesPerLine(), bits(), and jumpTable().
Example: desktop/desktop.cpp.
void QImage::setAlphaBuffer ( bool enable )
Enables alpha buffer mode if enable is TRUE, otherwise disables it. The
default setting is disabled.
An 8-bpp image has 8-bit pixels. A pixel is an index into the color
table, which contains 32-bit color values. In a 32-bpp image, the
32-bit pixels are the color values.
This 32-bit value is encoded as follows: The lower 24 bits are used for
the red, green, and blue components. The upper 8 bits contain the alpha
component.
The alpha component specifies the transparency of a pixel. 0 means
completely transparent and 255 means opaque. The alpha component is
ignored if you do not enable alpha buffer mode.
The alpha buffer is used to set a mask when a QImage is translated to a
QPixmap.
See also hasAlphaBuffer() and createAlphaMask().
void QImage::setColor ( int i, QRgb c )
Sets a color in the color table at index i to c.
A color value is an RGB triplet. Use the qRgb() function (defined in
qcolor.h) to make RGB triplets.
See also color(), setNumColors(), and numColors().
Examples:
void QImage::setDotsPerMeterX ( int x )
Sets the value returned by dotsPerMeterX() to x.
void QImage::setDotsPerMeterY ( int y )
Sets the value returned by dotsPerMeterY() to y.
void QImage::setNumColors ( int numColors )
Resizes the color table to numColors colors.
If the color table is expanded all the extra colors will be set to
black (RGB 0,0,0).
See also numColors(), color(), setColor(), and colorTable().
void QImage::setOffset ( const QPoint & p )
Sets the value returned by offset() to p.
void QImage::setPixel ( int x, int y, uint index_or_rgb )
Sets the pixel index or color at the coordinates (x, y) to
index_or_rgb.
If (x, y) is not valid, the result is undefined.
If the image is a paletted image (depth() <= 8) and index_or_rgb >=
numColors(), the result is undefined.
See also pixelIndex(), pixel(), qRgb(), qRgba(), and valid().
void QImage::setText ( const char * key, const char * lang, const QString & s
)
Records string s for the keyword key. The key should be a portable
keyword recognizable by other software - some suggested values can be
found in the PNG specification. s can be any text. lang should specify
the language code (see RFC 1766) or 0.
QSize QImage::size () const
Returns the size of the image, i.e. its width and height.
See also width(), height(), and rect().
QImage QImage::smoothScale ( int w, int h, ScaleMode mode = ScaleFree ) const
Returns a smoothly scaled copy of the image. The returned image has a
size of width w by height h pixels if mode is ScaleFree. The modes
ScaleMin and ScaleMax may be used to preserve the ratio of the image:
if mode is ScaleMin, the returned image is guaranteed to fit into the
rectangle specified by w and h (it is as large as possible within the
constraints); if mode is ScaleMax, the returned image fits at least
into the specified rectangle (it is a small as possible within the
constraints).
For 32-bpp images and 1-bpp/8-bpp color images the result will be
32-bpp, whereas all-gray images (including black-and-white 1-bpp) will
produce 8-bit grayscale images with the palette spanning 256 grays from
black to white.
This function uses code based on pnmscale.c by Jef Poskanzer.
pnmscale.c - read a portable anymap and scale it
Copyright (C) 1989, 1991 by Jef Poskanzer.
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation. This software is provided "as is" without
express or implied warranty.
See also scale() and mirror().
QImage QImage::smoothScale ( const QSize & s, ScaleMode mode = ScaleFree )
const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
The requested size of the image is s.
QImage QImage::swapRGB () const
Returns a QImage in which the values of the red and blue components of
all pixels have been swapped, effectively converting an RGB image to a
BGR image. The original QImage is not changed.
Endian QImage::systemBitOrder () [static]
Determines the bit order of the display hardware. Returns
QImage::LittleEndian (LSB first) or QImage::BigEndian (MSB first).
See also systemByteOrder().
Endian QImage::systemByteOrder () [static]
Determines the host computer byte order. Returns QImage::LittleEndian
(LSB first) or QImage::BigEndian (MSB first).
See also systemBitOrder().
QString QImage::text ( const char * key, const char * lang = 0 ) const
Returns the string recorded for the keyword key in language lang, or in
a default language if lang is 0.
QString QImage::text ( const QImageTextKeyLang & kl ) const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns the string recorded for the keyword and language kl.
QStringList QImage::textKeys () const
Returns the keywords for which some texts are recorded.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = myImage.textKeys();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See also textList(), text(), setText(), and textLanguages().
QStringList QImage::textLanguages () const
Returns the language identifiers for which some texts are recorded.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = myImage.textLanguages();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See also textList(), text(), setText(), and textKeys().
QValueList<;QImageTextKeyLang> QImage::textList () const
Returns a list of QImageTextKeyLang objects that enumerate all the
texts key/language pairs set by setText() for this image.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QValueList<QImageTextKeyLang> list = myImage.textList();
QValueList<QImageTextKeyLang>::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
bool QImage::valid ( int x, int y ) const
Returns TRUE if ( x, y ) is a valid coordinate in the image; otherwise
returns FALSE.
See also width(), height(), and pixelIndex().
Examples:
int QImage::width () const
Returns the width of the image.
See also height(), size(), and rect().
Examples:
QImage QImage::xForm ( const QWMatrix & matrix ) const
Returns a copy of the image that is transformed using the
transformation matrix, matrix.
The transformation matrix is internally adjusted to compensate for
unwanted translation, i.e. xForm() returns the smallest image that
contains all the transformed points of the original image.
See also scale(), QPixmap::xForm(), QPixmap::trueMatrix(), and
QWMatrix.
RELATED FUNCTION DOCUMENTATIONvoid bitBlt ( QImage * dst, int dx, int dy, const QImage * src, int sx, int
sy, int sw, int sh, int conversion_flags )
Copies a block of pixels from src to dst. The pixels copied from source
(src) are converted according to conversion_flags if it is incompatible
with the destination (dst).
sx, sy is the top-left pixel in src, dx, dy is the top-left position in
dst and sw, \sh is the size of the copied block.
The copying is clipped if areas outside src or dst are specified.
If sw is -1, it is adjusted to src->width(). Similarly, if sh is -1, it
is adjusted to src->height().
Currently inefficient for non 32-bit images.
QDataStream & operator<;< ( QDataStream & s, const QImage & image )
Writes the image image to the stream s as a PNG image, or as a BMP
image if the stream's version is 1.
Note that writing the stream to a file will not produce a valid image
file.
See also QImage::save() and Format of the QDataStream operators.
QDataStream & operator>> ( QDataStream & s, QImage & image )
Reads an image from the stream s and stores it in image.
See also QImage::load() and Format of the QDataStream operators.
SEE ALSO
http://doc.trolltech.com/qimage.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports help us to
help you. Thank you.
The definitive Qt documentation is provided in HTML format; it is
located at $QTDIR/doc/html and can be read using Qt Assistant or with a
web browser. This man page is provided as a convenience for those users
who prefer man pages, although this format is not officially supported
by Trolltech.
If you find errors in this manual page, please report them to qt-
bugs@trolltech.com. Please include the name of the manual page
(qimage.3qt) and the Qt version (3.3.8).
Trolltech AS 2 February 2007 QImage(3qt)
