QImage Class | Qt GUI 5.5
QImage Class
class provides a hardware-independent image representation that allows direct access to the pixel data, and can be used as a paint device.
Header: #include &QImage&
qmake: QT += gui Inherits: Note: All functions in this class are .
Public Types
{ Format_Invalid, Format_Mono, Format_MonoLSB, Format_Indexed8, ..., Format_Grayscale8 }
{ InvertRgb, InvertRgba }
Public Functions
(const QSize & size, Format format)
(int width, int height, Format format)
(uchar * data, int width, int height, Format format, QImageCleanupFunction cleanupFunction = 0, void * cleanupInfo = 0)
(const uchar * data, int width, int height, Format format, QImageCleanupFunction cleanupFunction = 0, void * cleanupInfo = 0)
(uchar * data, int width, int height, int bytesPerLine, Format format, QImageCleanupFunction cleanupFunction = 0, void * cleanupInfo = 0)
(const uchar * data, int width, int height, int bytesPerLine, Format format, QImageCleanupFunction cleanupFunction = 0, void * cleanupInfo = 0)
(const char * const[] xpm)
(const QString & fileName, const char * format = 0)
(const QImage & image)
(QImage && other)
bool () const
int () const
uchar * ()
const uchar * () const
int () const
int () const
qint64 () const
QRgb (int i) const
int () const
QVector&QRgb& () const
const uchar * () const
const uchar * (int i) const
QImage (Format format, Qt::ImageConversionFlags flags = Qt::AutoColor) const
QImage (Format format, const QVector&QRgb& & colorTable, Qt::ImageConversionFlags flags = Qt::AutoColor) const
QImage (const QRect & rectangle = QRect()) const
QImage (int x, int y, int width, int height) const
QImage (Qt::ImageConversionFlags flags = Qt::AutoColor) const
QImage (bool clipTight = true) const
QImage (QRgb color, Qt::MaskMode mode = Qt::MaskInColor) const
int () const
qreal () const
int () const
int () const
void (uint pixelValue)
void (const QColor & color)
void (Qt::GlobalColor color)
Format () const
bool () const
int () const
void (InvertMode mode = InvertRgb)
bool () const
bool () const
bool (const QString & fileName, const char * format = 0)
bool (QIODevice * device, const char * format)
bool (const uchar * data, int len, const char * format = 0)
bool (const QByteArray & data, const char * format = 0)
QImage (bool horizontal = false, bool vertical = true) const
QPoint () const
QRgb (const QPoint & position) const
QRgb (int x, int y) const
QPixelFormat () const
int (const QPoint & position) const
int (int x, int y) const
QRect () const
QImage () const
bool (const QString & fileName, const char * format = 0, int quality = -1) const
bool (QIODevice * device, const char * format = 0, int quality = -1) const
QImage (const QSize & size, Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio, Qt::TransformationMode transformMode = Qt::FastTransformation) const
QImage (int width, int height, Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio, Qt::TransformationMode transformMode = Qt::FastTransformation) const
QImage (int height, Qt::TransformationMode mode = Qt::FastTransformation) const
QImage (int width, Qt::TransformationMode mode = Qt::FastTransformation) const
uchar * (int i)
const uchar * (int i) const
void (int index, QRgb colorValue)
void (int colorCount)
void (const QVector&QRgb& & colors)
void (qreal scaleFactor)
void (int x)
void (int y)
void (const QPoint & offset)
void (const QPoint & position, uint index_or_rgb)
void (int x, int y, uint index_or_rgb)
void (const QString & key, const QString & text)
QSize () const
void (QImage & other)
QString (const QString & key = QString()) const
QStringList () const
QImage (const QMatrix & matrix, Qt::TransformationMode mode = Qt::FastTransformation) const
QImage (const QTransform & matrix, Qt::TransformationMode mode = Qt::FastTransformation) const
bool (const QPoint & pos) const
bool (int x, int y) const
int () const
bool (const QImage & image) const
QImage & (const QImage & image)
QImage & (QImage && other)
bool (const QImage & image) const
13 public functions inherited from
Static Public Members
QImage (const uchar * data, int size, const char * format = 0)
QImage (const QByteArray & data, const char * format = 0)
QImage::Format (QPixelFormat format)
QPixelFormat (QImage::Format format)
QMatrix (const QMatrix & matrix, int width, int height)
QTransform (const QTransform & matrix, int width, int height)
Protected Functions
QImage (int w, int h) const
1 protected function inherited from
Related Non-Members
QDataStream & (QDataStream & stream, const QImage & image)
QDataStream & (QDataStream & stream, QImage & image)
Detailed Description
class provides a hardware-independent image representation that allows direct access to the pixel data, and can be used as a paint device.
Qt provides four classes for handling image data: , ,
is designed and optimized for I/O, and for direct pixel access and manipulation, while
is designed and optimized for showing images on screen.
is only a convenience class that inherits , ensuring a depth of 1. Finally, the
class is a paint device that records and replays
can be used to draw directly onto images. When using
on a , the painting can be performed in another thread than the current GUI thread.
class supports several image formats described by the
enum. These include monochrome, 8-bit, 32-bit and alpha-blended images which are available in all versions of Qt 4.x.
provides a collection of functions that can be used to obtain a variety of information about the image. There are also several functions that enables transformation of the image.
objects can be passed around by value since the
class uses .
objects can also be streamed and compared.
Note: If you would like to load
objects in a static build of Qt, refer to the .Warning: Painting on a
with the format
is not supported.
Reading and Writing Image Files
provides several ways of loading an image file: The file can be loaded when constructing the
object, or by using the () or () functions later on.
also provides the static () function, constructing a
from the given data. When loading an image, the file name can either refer to an actual file on disk or to one of the application's embedded resources. See
overview for details on how to embed images and other resource files in the application's executable.
Simply call the () function to save a
The complete list of supported file formats are available through the () and () functions. New file formats can be added as plugins. By default, Qt supports the following formats:
FormatDescriptionQt's support
BMPWindows BitmapRead/write
GIFGraphic Interchange Format (optional)Read
JPGJoint Photographic Experts GroupRead/write
JPEGJoint Photographic Experts GroupRead/write
PNGPortable Network GraphicsRead/write
PBMPortable BitmapRead
PGMPortable GraymapRead
PPMPortable PixmapRead/write
XBMX11 BitmapRead/write
XPMX11 PixmapRead/write
Image Information
provides a collection of functions that can be used to obtain a variety of information about the image:
Available Functions
GeometryThe (), (), (), (), and () functions provide information about the image size and aspect ratio.The () function returns the image's enclosing rectangle. The () function tells if a given pair of coordinates is within this rectangle. The () function returns the number of pixels by which the image is intended to be offset by when positioned relative to other images, which also can be manipulated using the () function.
ColorsThe color of a pixel can be retrieved by passing its coordinates to the () function. The () function returns the color as a
value indepedent of the image's format.In case of monochrome and 8-bit images, the () and () functions provide information about the color components used to store the image data: The () function returns the image's entire color table. To obtain a single entry, use the () function to retrieve the pixel index for a given pair of coordinates, then use the () function to retrieve the color. Note that if you create an 8-bit image manually, you have to set a valid color table on the image as well.
The () function tells if the image's format respects the alpha channel, or not. The () and () functions tell whether an image's colors are all shades of gray.
See also the
TextThe () function returns the image text associated with the given text key. An image's text keys can be retrieved using the () function. Use the () function to alter an image's text.
Low-level informationThe () function returns the depth of the image. The supported depths are 1 (monochrome), 8, 16, 24 and 32 bits. The () function tells how many of those bits that are used. For more information see the
section.The (), (), and () functions provide low-level information about the data stored in the image.
The () function returns a number that uniquely identifies the contents of this
Pixel Manipulation
The functions used to manipulate an image's pixels depend on the image format. The reason is that monochrome and 8-bit images are index-based and use a color lookup table, while 32-bit images store ARGB values directly. For more information on image formats, see the
In case of a 32-bit image, the () function can be used to alter the color of the pixel at the given coordinates to any other color specified as an ARGB quadruplet. To make a suitable
value, use the () (adding a default alpha component to the given RGB values, i.e. creating an opaque color) or () function. For example:
image(3, 3, ::Format_RGB32);
value = (189, 149, 39);
image.setPixel(1, 1, value);
value = (122, 163, 39);
image.setPixel(0, 1, value);
image.setPixel(1, 0, value);
value = (237, 187, 51);
image.setPixel(2, 1, value);
In case of a 8-bit and monchrome images, the pixel value is only an index from the image's color table. So the () function can only be used to alter the color of the pixel at the given coordinates to a predefined color from the image's color table, i.e. it can only change the pixel's index value. To alter or add a color to an image's color table, use the () function.
An entry in the color table is an ARGB quadruplet encoded as an
value. Use the () and () functions to make a suitable
value for use with the () function. For example:
image(3, 3, ::Format_Indexed8);
value = (122, 163, 39);
image.setColor(0, value);
value = (237, 187, 51);
image.setColor(1, value);
value = (189, 149, 39);
image.setColor(2, value);
image.setPixel(0, 1, 0);
image.setPixel(1, 0, 0);
image.setPixel(1, 1, 2);
image.setPixel(2, 1, 1);
also provide the () function which returns a pointer to the pixel data at the scanline with the given index, and the () function which returns a pointer to the first pixel data (this is equivalent to scanLine(0)).
Image Formats
Each pixel stored in a
is represented by an integer. The size of the integer varies depending on the format.
supports several image formats described by the
Monochrome images are stored using 1-bit indexes into a color table with at most two colors. There are two different types of monochrome images: big endian (MSB first) or little endian (LSB first) bit order.
8-bit images are stored using 8-bit indexes into a color table, i.e. they have a single byte per pixel. The color table is a &&, and the
typedef is equivalent to an unsigned int containing an ARGB quadruplet on the format 0xAARRGGBB.
32-bit images instead, each pixel contains an
value. There are three different types of 32-bit images storing RGB (i.e. 0xffRRGGBB), ARGB and premultiplied ARGB values respectively. In the premultiplied format the red, green, and blue channels are multiplied by the alpha component divided by 255.
An image's format can be retrieved using the () function. Use the () functions to convert an image into another format. The () and () functions tell whether a color image can safely be converted to a grayscale image.
Image Transformations
supports a number of functions for creating a new image that is a transformed version of the original: The () function builds and returns a 1-bpp mask from the alpha buffer in this image, and the () function creates and returns a 1-bpp heuristic mask for this image. The latter function works by selecting a color from one of the corners, then chipping away pixels of that color starting at all the edges.
The () function returns a mirror of the image in the desired direction, the () returns a copy of the image scaled to a rectangle of the desired measures, and the () function constructs a BGR image from a RGB image.
The () and () functions return scaled copies of the image.
The () function returns a copy of the image that is transformed with the given transformation matrix and transformation mode: Internally, the transformation matrix is adjusted to compensate for unwanted translation, i.e. () returns the smallest image containing all transformed points of the original image. The static () function returns the actual matrix used for transforming the image.
There are also functions for changing attributes of an image in-place:
FunctionDescription
()Defines the aspect ratio by setting the number of pixels that fit horizontally in a physical meter.
()Defines the aspect ratio by setting the number of pixels that fit vertically in a physical meter.
()Fills the entire image with the given pixel value.
()Inverts all pixel values in the image using the given
()Sets the color table used to translate color indexes. Only monochrome and 8-bit formats.
()Resizes the color table. Only monochrome and 8-bit formats.
Legal Information
For smooth scaling, the () functions use code based on smooth scaling algorithm by Daniel M. Duley.
Copyright (C)
Daniel M. Duley
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
See also , , , , , , , and .
Member Type Documentation
enum QImage::Format
The following image formats are available in Qt. Values from Format_ARGB8565_Premultiplied to Format_ARGB4444_Premultiplied were added in Qt 4.4. Values Format_RGBX8888, Format_RGBA8888 and Format_RGBA8888_Premultiplied were added in Qt 5.2. Values Format_BGR30, Format_A2BGR30_Premultiplied, Format_RGB30, Format_A2RGB30_Premultiplied were added in Qt 5.4. Format_Alpha8 and Format_Grayscale8 were added in Qt 5.5. See the notes after the table.
ConstantValueDescription
QImage::Format_Invalid0The image is invalid.
QImage::Format_Mono1The image is stored using 1-bit per pixel. Bytes are packed with the most significant bit (MSB) first.
QImage::Format_MonoLSB2The image is stored using 1-bit per pixel. Bytes are packed with the less significant bit (LSB) first.
QImage::Format_Indexed83The image is stored using 8-bit indexes into a colormap.
QImage::Format_RGB324The image is stored using a 32-bit RGB format (0xffRRGGBB).
QImage::Format_ARGB325The image is stored using a 32-bit ARGB format (0xAARRGGBB).
QImage::Format_ARGB32_Premultiplied6The image is stored using a premultiplied 32-bit ARGB format (0xAARRGGBB), i.e. the red, green, and blue channels are multiplied by the alpha component divided by 255. (If RR, GG, or BB has a higher value than the alpha channel, the results are undefined.) Certain operations (such as image composition using alpha blending) are faster using premultiplied ARGB32 than with plain ARGB32.
QImage::Format_RGB167The image is stored using a 16-bit RGB format (5-6-5).
QImage::Format_ARGB8565_Premultiplied8The image is stored using a premultiplied 24-bit ARGB format (8-5-6-5).
QImage::Format_RGB6669The image is stored using a 24-bit RGB format (6-6-6). The unused most significant bits is always zero.
QImage::Format_ARGB6666_Premultiplied10The image is stored using a premultiplied 24-bit ARGB format (6-6-6-6).
QImage::Format_RGB55511The image is stored using a 16-bit RGB format (5-5-5). The unused most significant bit is always zero.
QImage::Format_ARGB8555_Premultiplied12The image is stored using a premultiplied 24-bit ARGB format (8-5-5-5).
QImage::Format_RGB88813The image is stored using a 24-bit RGB format (8-8-8).
QImage::Format_RGB44414The image is stored using a 16-bit RGB format (4-4-4). The unused bits are always zero.
QImage::Format_ARGB4444_Premultiplied15The image is stored using a premultiplied 16-bit ARGB format (4-4-4-4).
QImage::Format_RGBX888816The image is stored using a 32-bit byte-ordered RGB(x) format (8-8-8-8). This is the same as the Format_RGBA8888 except alpha must always be 255.
QImage::Format_RGBA888817The image is stored using a 32-bit byte-ordered RGBA format (8-8-8-8). Unlike ARGB32 this is a byte-ordered format, which means the 32bit encoding differs between big endian and little endian architectures, being respectively (0xRRGGBBAA) and (0xAABBGGRR). The order of the colors is the same on any architecture if read as bytes 0xRR,0xGG,0xBB,0xAA.
QImage::Format_RGBA8888_Premultiplied18The image is stored using a premultiplied 32-bit byte-ordered RGBA format (8-8-8-8).
QImage::Format_BGR3019The image is stored using a 32-bit BGR format (x-10-10-10).
QImage::Format_A2BGR30_Premultiplied20The image is stored using a 32-bit premultiplied ABGR format (2-10-10-10).
QImage::Format_RGB3021The image is stored using a 32-bit RGB format (x-10-10-10).
QImage::Format_A2RGB30_Premultiplied22The image is stored using a 32-bit premultiplied ARGB format (2-10-10-10).
QImage::Format_Alpha823The image is stored using an 8-bit alpha only format.
QImage::Format_Grayscale824The image is stored using an 8-bit grayscale format.
Note: Drawing into a
with QImage::Format_Indexed8 is not supported.Note: Do not render into ARGB32 images using . Using QImage::Format_ARGB32_Premultiplied is significantly faster.Note: Formats with more than 8 bit per color channel will only be processed by the raster engine using 8 bit per color.See also () and ().
enum QImage::InvertMode
This enum type is used to describe how pixel values should be inverted in the () function.
ConstantValueDescription
QImage::InvertRgb0Invert only the RGB values and leave the alpha channel unchanged.
QImage::InvertRgba1Invert all channels, including the alpha channel.
See also ().
Member Function Documentation
QImage::QImage()
Constructs a null image.
See also ().
QImage::QImage(const
Constructs an image with the given size and format.
image is returned if memory cannot be allocated.
Warning: This will create a
with uninitialized data. Call () to fill the image with an appropriate pixel value before drawing onto it with .
QImage::QImage(int width, int height,
Constructs an image with the given width, height and format.
image will be returned if memory cannot be allocated.
Warning: This will create a
with uninitialized data. Call () to fill the image with an appropriate pixel value before drawing onto it with .
QImage::QImage( * data, int width, int height,
cleanupFunction = 0, void * cleanupInfo = 0)
Constructs an image with the given width, height and format, that uses an existing memory buffer, data. The width and height must be specified in pixels, data must be 32-bit aligned, and each scanline of data in the image must also be 32-bit aligned.
The buffer must remain valid throughout the life of the
and all copies that have not been modified or otherwise detached from the original buffer. The image does not delete the buffer at destruction. You can provide a function pointer cleanupFunction along with an extra pointer cleanupInfo that will be called when the last copy is destroyed.
If format is an indexed color format, the image color table is initially empty and must be sufficiently expanded with () or () before the image is used.
QImage::QImage(const
* data, int width, int height,
cleanupFunction = 0, void * cleanupInfo = 0)
Constructs an image with the given width, height and format, that uses an existing read-only memory buffer, data. The width and height must be specified in pixels, data must be 32-bit aligned, and each scanline of data in the image must also be 32-bit aligned.
The buffer must remain valid throughout the life of the
and all copies that have not been modified or otherwise detached from the original buffer. The image does not delete the buffer at destruction. You can provide a function pointer cleanupFunction along with an extra pointer cleanupInfo that will be called when the last copy is destroyed.
If format is an indexed color format, the image color table is initially empty and must be sufficiently expanded with () or () before the image is used.
Unlike the similar
constructor that takes a non-const data buffer, this version will never alter the contents of the buffer. For example, calling () will return a deep copy of the image, rather than the buffer passed to the constructor. This allows for the efficiency of constructing a
from raw data, without the possibility of the raw data being changed.
QImage::QImage( * data, int width, int height, int bytesPerLine,
cleanupFunction = 0, void * cleanupInfo = 0)
Constructs an image with the given width, height and format, that uses an existing memory buffer, data. The width and height must be specified in pixels. bytesPerLine specifies the number of bytes per line (stride).
The buffer must remain valid throughout the life of the
and all copies that have not been modified or otherwise detached from the original buffer. The image does not delete the buffer at destruction. You can provide a function pointer cleanupFunction along with an extra pointer cleanupInfo that will be called when the last copy is destroyed.
If format is an indexed color format, the image color table is initially empty and must be sufficiently expanded with () or () before the image is used.
QImage::QImage(const
* data, int width, int height, int bytesPerLine,
cleanupFunction = 0, void * cleanupInfo = 0)
Constructs an image with the given width, height and format, that uses an existing memory buffer, data. The width and height must be specified in pixels. bytesPerLine specifies the number of bytes per line (stride).
The buffer must remain valid throughout the life of the
and all copies that have not been modified or otherwise detached from the original buffer. The image does not delete the buffer at destruction. You can provide a function pointer cleanupFunction along with an extra pointer cleanupInfo that will be called when the last copy is destroyed.
If format is an indexed color format, the image color table is initially empty and must be sufficiently expanded with () or () before the image is used.
Unlike the similar
constructor that takes a non-const data buffer, this version will never alter the contents of the buffer. For example, calling () will return a deep copy of the image, rather than the buffer passed to the constructor. This allows for the efficiency of constructing a
from raw data, without the possibility of the raw data being changed.
QImage::QImage(const char * const[] xpm)
Constructs an image from the given xpm image.
Make sure that the image is 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 able to be stored in ROM with the application.
QImage::QImage(const
& fileName, const char * format = 0)
Constructs an image and tries to load the image from the file with the given fileName.
The loader attempts to read the image using the specified format. If the format is not specified (which is the default), the loader probes the file for a header to guess the file format.
If the loading of the image failed, this object is a null image.
The file name can either refer to an actual file on disk or to one of the application's embedded resources. See the
overview for details on how to embed images and other resource files in the application's executable.
See also () and .
QImage::QImage(const
Constructs a shallow copy of the given image.
For more information about shallow copies, see the
documentation.
See also ().
QImage::QImage( && other)
Move-constructs a
instance, making it point at the same object that other was pointing to.
This function was introduced in
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 false.
Note that this function is slow for images without color table.
See also ().
int QImage::bitPlaneCount() const
Returns the number of bit planes in the image.
The number of bit planes is the number of bits of color and transparency information for each pixel. This is different from (i.e. smaller than) the depth when the image format contains unused bits.
This function was introduced in
See also (), (), and .
* QImage::bits()
Returns a pointer to the first pixel data. This is equivalent to (0).
uses . This function performs a deep copy of the shared pixel data, thus ensuring that this
is the only one using the current return value.
See also (), (), and ().
* QImage::bits() const
This is an overloaded function.
uses , but this function does not perform a deep copy of the shared pixel data, because the returned data is const.
int QImage::byteCount() const
Returns the number of bytes occupied by the image data.
This function was introduced in
See also (), (), and .
int QImage::bytesPerLine() const
Returns the number of bytes per image scanline.
This is equivalent to () / ().
See also ().
QImage::cacheKey() const
Returns a number that identifies the contents of this
object. Distinct
objects can only have the same key if they refer to the same contents.
The key will change when the image is altered.
QImage::color(int i) const
Returns the color in the color table at index i. The first color is at index 0.
The colors in an image's color table are specified as ARGB quadruplets (). Use the (), (), (), and () functions to get the color value components.
See also (), (), and .
int QImage::colorCount() const
Returns the size of the color table for the image.
Notice that colorCount() returns 0 for 32-bpp images because these images do not use color tables, but instead encode pixel values as ARGB quadruplets.
This function was introduced in
See also () and .
&& QImage::colorTable() const
Returns a list of the colors contained in the image's color table, or an empty list if the image does not have a color table
See also (), (), and ().
* QImage::constBits() const
Returns a pointer to the first pixel data.
uses , but this function does not perform a deep copy of the shared pixel data, because the returned data is const.
This function was introduced in
See also () and ().
* QImage::constScanLine(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.
uses , but this function does not perform a deep copy of the shared pixel data, because the returned data is const.
This function was introduced in
See also () and ().
QImage::convertToFormat( format,
flags = Qt::AutoColor) const
Returns a copy of the image in the given format.
The specified image conversion flags control how the image data is handled during the conversion process.
See also .
QImage::convertToFormat( format, const && & colorTable,
flags = Qt::AutoColor) const
This is an overloaded function.
Returns a copy of the image converted to the given format, using the specified colorTable.
Conversion from 32 bit to 8 bit indexed is a slow operation and will use a straightforward nearest color approach, with no dithering.
QImage::copy(const
& rectangle = QRect()) const
Returns a sub-area of the image as a new image.
The returned image is copied from the position (rectangle.x(), rectangle.y()) in this image, and will always have the size of the given rectangle.
In areas beyond this image, pixels are set to 0. For 32-bit RGB images, for 32-bit ARGB images, this mea for 8-bit images, this means the color with index 0 in the color table w for 1-bit images, this means .
If the given rectangle is a null rectangle the entire image is copied.
See also ().
QImage::copy(int x, int y, int width, int height) const
This is an overloaded function.
The returned image is copied from the position (x, y) in this image, and will always have the given width and height. In areas beyond this image, pixels are set to 0.
QImage::createAlphaMask( flags = Qt::AutoColor) const
Builds and returns a 1-bpp mask from the alpha buffer in this image. Returns a null image if the image's format is .
The flags argument is a bitwise-OR of the , and controls the conversion process. Passing 0 for flags sets all the default options.
The returned image has little-endian bit order (i.e. the image's format is ), which you can convert to big-endian () using the () function.
See also () and .
QImage::createHeuristicMask(bool clipTight = true) const
Creates and returns a 1-bpp heuristic mask for this image.
The function 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 (i.e. the image's format is ), which you can convert to big-endian () using the () function.
If clipTight is true (the default) the mask is just large enough otherwise, the mask is larger than the data pixels.
Note that this function disregards the alpha buffer.
See also () and .
QImage::createMaskFromColor( color,
mode = Qt::MaskInColor) const
Creates and returns a mask for this image based on the given color value. If the mode is MaskInColor (the default value), all pixels matching color will be opaque pixels in the mask. If mode is MaskOutColor, all pixels matching the given color will be transparent.
See also () and ().
int QImage::depth() const
Returns the depth of the image.
The image depth is the number of bits used to store a single pixel, also called bits per pixel (bpp).
The supported depths are 1, 8, 16, 24 and 32.
See also (), (), , and .
QImage::devicePixelRatio() const
Returns the device pixel ratio for the image. This is the ratio between device pixels and device independent pixels.
Use this function when calculating layout geometry based on the image size:
layoutSize = image.() / image.devicePixelRatio()
The default value is 1.0.
See also () and .
int QImage::dotsPerMeterX() const
Returns the number of pixels that fit horizontally in a physical meter. Together with (), this number defines the intended scale and aspect ratio of the image.
See also () and .
int QImage::dotsPerMeterY() const
Returns the number of pixels that fit vertically in a physical meter. Together with (), this number defines the intended scale and aspect ratio of the image.
See also () and .
void QImage::fill( pixelValue)
Fills the entire image with the given pixelValue.
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 and if the depth is 16 the lowest 16 bits are used.
Note: () returns the color of the pixel at the given coordinates while QColor::pixel() returns the pixel value of the underlying window system (essentially an index value), so normally you will want to use () to use a color from an existing image or () to use a specific color.
See also () and .
void QImage::fill(const
This is an overloaded function.
Fills the entire image with the given color.
If the depth of the image is 1, the image will be filled with 1 if color it will otherwise be filled with 0.
If the depth of the image is 8, the image will be filled with the index corresponding the color in the co it will otherwise be filled with 0.
This function was introduced in
void QImage::fill( color)
This is an overloaded function.
Fills the image with the given color, described as a standard global color.
This function was introduced in
QImage::format() const
Returns the format of the image.
See also .
QImage::fromData(const
* data, int size, const char * format = 0)
Constructs a
from the first size bytes of the given binary data. The loader attempts to read the image using the specified format. If format is not specified (which is the default), the loader probes the file for a header to guess the file format. binary data. The loader attempts to read the image, either using the optional image format specified or by determining the image format from the data.
If format is not specified (which is the default), the loader probes the file for a header to determine the file format. If format is specified, it must be one of the values returned by ().
If the loading of the image fails, the image returned will be a null image.
See also (), (), and .
QImage::fromData(const
& data, const char * format = 0)
This is an overloaded function.
Loads an image from the given
bool QImage::hasAlphaChannel() const
Returns true if the image has a format that respects the alpha channel, otherwise returns false.
See also .
int QImage::height() const
Returns the height of the image.
See also .
void QImage::invertPixels( mode = InvertRgb)
Inverts all pixel values in the image.
The given invert mode only have a meaning when the image's depth is 32. The default mode is , which leaves the alpha channel unchanged. If the mode is , the alpha bits are also inverted.
Inverting an 8-bit image means to replace all pixels using color index i with a pixel using color index 255 minus i. The same is the case for a 1-bit image. Note that the color table is not changed.
If the image has a premultiplied alpha channel, the image is first converted to ARGB32 to be inverted and then converted back.
See also .
bool QImage::isGrayscale() const
For 32-bit images, this function is equivalent to ().
For color indexed images, this function returns true if color(i) is (i, i, i) for all indexe otherwise returns false.
See also () and .
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.
bool QImage::load(const
& fileName, const char * format = 0)
Loads an image from the file with the given fileName. Returns true if the image was otherwise invalidates the image and returns false.
The loader attempts to read the image using the specified format, e.g., PNG or JPG. If format is not specified (which is the default), the loader probes the file for a header to guess the file format.
The file name can either refer to an actual file on disk or to one of the application's embedded resources. See the
overview for details on how to embed images and other resource files in the application's executable.
See also .
bool QImage::load( * device, const char * format)
This is an overloaded function.
This function reads a
from the given device. This can, for example, be used to load an image directly into a .
bool QImage::loadFromData(const
* data, int len, const char * format = 0)
Loads an image from the first len bytes of the given binary data. Returns true if the image was otherwise invalidates the image and returns false.
The loader attempts to read the image using the specified format, e.g., PNG or JPG. If format is not specified (which is the default), the loader probes the file for a header to guess the file format.
See also .
bool QImage::loadFromData(const
& data, const char * format = 0)
This is an overloaded function.
Loads an image from the given
QImage::mirrored(bool horizontal = false, bool vertical = true) const
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.
Note that the original image is not changed.
See also .
QImage::offset() const
Returns the number of pixels by which the image is intended to be offset by when positioning relative to other images.
See also () and .
QImage::pixel(const
& position) const
Returns the color of the pixel at the given position.
If the position is not valid, the results are undefined.
Warning: This function is expensive when used for massive pixel manipulations.
See also (), (), and .
QImage::pixel(int x, int y) const
This is an overloaded function.
Returns the color of the pixel at coordinates (x, y).
QImage::pixelFormat() const
Returns the
int QImage::pixelIndex(const
& position) const
Returns the pixel index at the given position.
If position is not valid, or if the image is not a paletted image (() & 8), the results are undefined.
See also (), (), and .
int QImage::pixelIndex(int x, int y) const
This is an overloaded function.
Returns the pixel index at (x, y).
QImage::rect() const
Returns the enclosing rectangle (0, 0, (), ()) of the image.
See also .
QImage::rgbSwapped() const
in which the values of the red and blue components of all pixels have been swapped, effectively converting an RGB image to an BGR image.
The original
is not changed.
See also .
bool QImage::save(const
& fileName, const char * format = 0, int quality = -1) const
Saves the image to the file with the given fileName, using the given image file format and quality factor. If format is 0,
will attempt to guess the format by looking at fileName's suffix.
The quality factor must be in the range 0 to 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 wa otherwise returns false.
See also .
bool QImage::save( * device, const char * format = 0, int quality = -1) const
This is an overloaded function.
This function writes a
to the given device.
This can, for example, be used to save an image directly into a :
buffer(&ba);
buffer.open(::WriteOnly);
image.save(&buffer, &PNG&);
QImage::scaled(const
aspectRatioMode = Qt::IgnoreAspectRatio,
transformMode = Qt::FastTransformation) const
Returns a copy of the image scaled to a rectangle defined by the given size according to the given aspectRatioMode and transformMode.
If aspectRatioMode is , the image is scaled to size.
If aspectRatioMode is , the image is scaled to a rectangle as large as possible inside size, preserving the aspect ratio.
If aspectRatioMode is , the image is scaled to a rectangle as small as possible outside size, preserving the aspect ratio.
If the given size is empty, this function returns a null image.
See also () and .
QImage::scaled(int width, int height,
aspectRatioMode = Qt::IgnoreAspectRatio,
transformMode = Qt::FastTransformation) const
This is an overloaded function.
Returns a copy of the image scaled to a rectangle with the given width and height according to the given aspectRatioMode and transformMode.
If either the width or the height is zero or negative, this function returns a null image.
QImage::scaledToHeight(int height,
mode = Qt::FastTransformation) const
Returns a scaled copy of the image. The returned image is scaled to the given height using the specified transformation mode.
This function automatically calculates the width of the image so that the ratio of the image is preserved.
If the given height is 0 or negative, a null image is returned.
See also .
QImage::scaledToWidth(int width,
mode = Qt::FastTransformation) const
Returns a scaled copy of the image. The returned image is scaled to the given width using the specified transformation mode.
This function automatically calculates the height of the image so that its aspect ratio is preserved.
If the given width is 0 or negative, a null image is returned.
See also .
* QImage::scanLine(int i)
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* ( 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. Use (), (), (), and () to access the pixels.
See also (), (), , and ().
* QImage::scanLine(int i) const
This is an overloaded function.
void QImage::setColor(int index,
colorValue)
Sets the color at the given index in the color table, to the given to colorValue. The color value is an ARGB quadruplet.
If index is outside the current size of the color table, it is expanded with ().
See also (), (), (), and .
void QImage::setColorCount(int colorCount)
Resizes the color table to contain colorCount entries.
If the color table is expanded, all the extra colors will be set to transparent (i.e (0, 0, 0, 0)).
When the image is used, the color table must be large enough to have entries for all the pixel/index values present in the image, otherwise the results are undefined.
This function was introduced in
See also (), (), (), and .
void QImage::setColorTable(const && & colors)
Sets the color table used to translate color indexes to
values, to the specified colors.
When the image is used, the color table must be large enough to have entries for all the pixel/index values present in the image, otherwise the results are undefined.
See also (), (), and .
void QImage::setDevicePixelRatio( scaleFactor)
Sets the device pixel ratio for the image. This is the ratio between image pixels and device-independent pixels.
The default scaleFactor is 1.0. Setting it to something else has two effects:
QPainters that are opened on the image will be scaled. For example, painting on a 200x200 image if with a ratio of 2.0 will result in effective (device-independent) painting bounds of 100x100.
Code paths in Qt that calculate layout geometry based on the image size will take the ratio into account:
layoutSize = image.() / image.() The net effect of this is that the image is displayed as high-DPI image rather than a large image (see ).
See also ().
void QImage::setDotsPerMeterX(int x)
Sets the number of pixels that fit horizontally in a physical meter, to x.
Together with (), this number defines the intended scale and aspect ratio of the image, and determines the scale at which
will draw graphics on the image. It does not change the scale or aspect ratio of the image when it is rendered on other paint devices.
See also () and .
void QImage::setDotsPerMeterY(int y)
Sets the number of pixels that fit vertically in a physical meter, to y.
Together with (), this number defines the intended scale and aspect ratio of the image, and determines the scale at which
will draw graphics on the image. It does not change the scale or aspect ratio of the image when it is rendered on other paint devices.
See also () and .
void QImage::setOffset(const
Sets the number of pixels by which the image is intended to be offset by when positioning relative to other images, to offset.
See also () and .
void QImage::setPixel(const
& position,
index_or_rgb)
Sets the pixel index or color at the given position to index_or_rgb.
If the image's format is either monochrome or 8-bit, the given index_or_rgb value must be an index in the image's color table, otherwise the parameter must be a
If position is not a valid coordinate pair in the image, or if index_or_rgb &= () in the case of monochrome and 8-bit images, the result is undefined.
Warning: This function is expensive due to the call of the internal detach() fu if performance is a concern, we recommend the use of
to access pixel data directly.
See also () and .
void QImage::setPixel(int x, int y,
index_or_rgb)
This is an overloaded function.
Sets the pixel index or color at (x, y) to index_or_rgb.
void QImage::setText(const
& key, const
Sets the image text to the given text and associate it with the given key.
If you just want to store a single text block (i.e., a &comment& or just a description), you can either pass an empty key, or use a generic key like &Description&.
The image text is embedded into the image data when you call () or ().
Not all image formats support embedded text. You can find out if a specific image or format supports embedding text by using (). We give an example:
writer.setFormat(&png&);
if (writer.supportsOption(::Description))
() && &Png supports embedded text&;
You can use () to find out which image formats are available to you.
See also () and ().
QImage::size() const
Returns the size of the image, i.e. its () and ().
See also .
[protected]
QImage::smoothScaled(int w, int h) const
Returns a smoothly scaled copy of the image. The returned image has a size of width w by height h pixels.
void QImage::swap( & other)
Swaps image other with this image. This operation is very fast and never fails.
This function was introduced in
QImage::text(const
& key = QString()) const
Returns the image text associated with the given key. If the specified key is an empty string, the whole image text is returned, with each key-text pair separated by a newline.
See also () and ().
QImage::textKeys() const
Returns the text keys for this image.
You can use these keys with () to list the image text for a certain key.
See also ().
QImage::toImageFormat( format)
Converts format into a
QImage::toPixelFormat( format)
Converts format into a
QImage::transformed(const
mode = Qt::FastTransformation) const
Returns a copy of the image that is transformed using the given transformation matrix and transformation mode.
The transformation matrix is internally adjusted to compensate for
i.e. the image produced is the smallest image that contains all the transformed points of the original image. Use the () function to retrieve the actual matrix used for transforming an image.
See also () and .
QImage::transformed(const
mode = Qt::FastTransformation) const
Returns a copy of the image that is transformed using the given transformation matrix and transformation mode.
The transformation matrix is internally adjusted to compensate for
i.e. the image produced is the smallest image that contains all the transformed points of the original image. Use the () function to retrieve the actual matrix used for transforming an image.
Unlike the other overload, this function can be used to perform perspective transformations on images.
See also () and .
QImage::trueMatrix(const
& matrix, int width, int height)
Returns the actual matrix used for transforming an image with the given width, height and matrix.
When transforming an image using the () function, the transformation matrix is internally adjusted to compensate for unwanted translation, i.e. () returns the smallest image containing all transformed points of the original image. This function returns the modified matrix, which maps points correctly from the original image into the new image.
See also () and .
QImage::trueMatrix(const
& matrix, int width, int height)
Returns the actual matrix used for transforming an image with the given width, height and matrix.
When transforming an image using the () function, the transformation matrix is internally adjusted to compensate for unwanted translation, i.e. () returns the smallest image containing all transformed points of the original image. This function returns the modified matrix, which maps points correctly from the original image into the new image.
Unlike the other overload, this function creates transformation matrices that can be used to perform perspective transformations on images.
See also () and .
bool QImage::valid(const
& pos) const
Returns true if pos is a valid coordinate p otherwise returns false.
See also () and ().
bool QImage::valid(int x, int y) const
This is an overloaded function.
Returns true if (x, y) is a valid coordinate p otherwise returns false.
int QImage::width() const
Returns the width of the image.
See also .
QImage::operator QVariant() const
Returns the image as a .
bool QImage::operator!=(const
& image) const
Returns true if this image and the given image hav 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 ().
& QImage::operator=(const
Assigns a shallow copy of the given image to this image and returns a reference to this image.
For more information about shallow copies, see the
documentation.
See also () and ().
& QImage::operator=( && other)
Move-assigns other to this
This function was introduced in
bool QImage::operator==(const
& image) const
Returns true if this image and the given image ha otherwise returns false.
The comparison can be slow, unless there is some obvious difference (e.g. different size or format), in which case the function will return quickly.
See also ().
Related Non-Members
typedef QImageCleanupFunction
A function with the following signature that can be used to implement basic image memory management:
void myImageCleanupHandler(void *info);
This typedef was introduced in
& operator&&( & stream, const
Writes the given image to the given stream 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 () and .
& operator&&( & stream,
Reads an image from the given stream and stores it in the given image.
See also () and .
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