Qt 5.6 | Qt GUI | C++ Classes | QImage

Qt 5.6.2 Reference Documentation

# Obsolete Members for QImage

The following members of class QImage are obsolete. They are provided to keep old source code working. We strongly advise against using them in new code.

## Public Functions

`(obsolete)` QImage | alphaChannel() const
`(obsolete)` int | numBytes() const
`(obsolete)` int | numColors() const
`(obsolete)` int | serialNumber() const
`(obsolete)` void | setAlphaChannel(const QImage &alphaChannel)
`(obsolete)` void | setNumColors(int n)
`(obsolete)` void | setText(const char *key, const char *language, const QString &text)
`(obsolete)` QString | text(const char *key, const char *language = Q_NULLPTR) const
`(obsolete)` QString | text(const QImageTextKeyLang &keywordAndLanguage) const
`(obsolete)` QStringList | textLanguages() const
`(obsolete)` QList<QImageTextKeyLang> | textList() const

## Member Function Documentation

### QImage QImage::alphaChannel() const

Returns the alpha channel of the image as a new grayscale QImage in which each pixel's red, green, and blue values are given the alpha value of the original image. The color depth of the returned image is 8-bit.

You can see an example of use of this function in QPixmap's alphaChannel(), which works in the same way as this function on QPixmaps.

Most usecases for this function can be replaced with QPainter and using composition modes.

Note this returns a color-indexed image if you want the alpha channel in the alpha8 format instead use convertToFormat(Format_Alpha8) on the source image.

Warning: This is an expensive function.

See also setAlphaChannel(), hasAlphaChannel(), convertToFormat(), Pixmap, and Image Transformations.

### int QImage::numBytes() const

Returns the number of bytes occupied by the image data.

See also byteCount().

### int QImage::numColors() const

Returns the size of the color table for the image.

See also setNumColors() and setColorCount().

### int QImage::serialNumber() const

Returns a number that identifies the contents of this QImage object. Distinct QImage objects can only have the same serial number if they refer to the same contents (but they don't have to).

Use cacheKey() instead.

Warning: The serial number doesn't necessarily change when the image is altered. This means that it may be dangerous to use it as a cache key.

See also operator==().

### void QImage::setAlphaChannel(const QImage &alphaChannel)

Sets the alpha channel of this image to the given alphaChannel.

If alphaChannel is an 8 bit grayscale image, the intensity values are written into this buffer directly. Otherwise, alphaChannel is converted to 32 bit and the intensity of the RGB pixel values is used.

Note that the image will be converted to the Format_ARGB32_Premultiplied format if the function succeeds.

Use one of the composition modes in QPainter::CompositionMode instead.

Warning: This function is expensive.

See also alphaChannel(), Image Transformations, and Image Formats.

### void QImage::setNumColors(int n)

Resizes the color table to contain n entries.

See also numColors() and setColorCount().

### void QImage::setText(const char *key, const char *language, const QString &text)

Sets the image text to the given text and associate it with the given key. The text is recorded in the specified language, or in a default language if language is 0.

Use setText() instead.

The language the text is recorded in is no longer relevant since the text is always set using QString and UTF-8 representation.

### QString QImage::text(const char *key, const char *language = Q_NULLPTR) const

Returns the text recorded for the given key in the given language, or in a default language if language is 0.

Use text() instead.

The language the text is recorded in is no longer relevant since the text is always set using QString and UTF-8 representation.

### QString QImage::text(const QImageTextKeyLang &keywordAndLanguage) const

This is an overloaded function.

Returns the text recorded for the given keywordAndLanguage.

Use text() instead.

The language the text is recorded in is no longer relevant since the text is always set using QString and UTF-8 representation.

### 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.

The language the text is recorded in is no longer relevant since the text is always set using QString and UTF-8 representation.

See also textKeys().

### QList<QImageTextKeyLang> QImage::textList() const

Returns a list of QImageTextKeyLang objects that enumerate all the texts key/language pairs set for this image.

The language the text is recorded in is no longer relevant since the text is always set using QString and UTF-8 representation.

See also textKeys().