QPixelFormat Class

Member Function Documentation

[constexpr noexcept] QPixelFormat::QPixelFormat()

Creates a null pixelformat. This format maps to QImage::Format_Invalid.

[constexpr noexcept] QPixelFormat::QPixelFormat(QPixelFormat::ColorModel colorModel, uchar firstSize, uchar secondSize, uchar thirdSize, uchar fourthSize, uchar fifthSize, uchar alphaSize, QPixelFormat::AlphaUsage alphaUsage, QPixelFormat::AlphaPosition alphaPosition, QPixelFormat::AlphaPremultiplied premultiplied, QPixelFormat::TypeInterpretation typeInterpretation, QPixelFormat::ByteOrder byteOrder = CurrentSystemEndian, uchar subEnum = 0)

Creates a QPixelFormat which assigns its data to the attributes. colorModel will be put into a buffer which is 4 bits long.

firstSize secondSize thirdSize fourthSize fifthSize alphaSize are all meant to represent the size of a channel. The channels will be used for different uses dependent on the colorModel. For RGB the firstSize will represent the Red channel. On CMYK it will represent the value of the Cyan channel.

alphaUsage represents if the alpha channel is used or not.

alphaPosition is the position of the alpha channel.

premultiplied represents if the alpha channel is already multiplied with the color channels.

typeInterpretation is how the pixel is interpreted.

byteOrder represents the endianness of the pixelformat. This defaults to CurrentSystemEndian, which will be resolve to the system's endianness for non-byte-ordered formats, and QPixelFormat::BigEndian for QPixelFormat::UnsignedByte.

subEnum is used for colorModels that have to store some extra information with supplying an extra enum. This is used by YUV to store the YUV type The default value is 0.

[constexpr noexcept] QPixelFormat::AlphaPosition QPixelFormat::alphaPosition() const

Accessor function for the position of the alpha channel relative to the color channels.

For formats where the individual channels map to individual units, the alpha position is relative to these units. For example for QImage::Format_RGBA16FPx4 which has an alpha position of QPixelFormat::AtEnd, the alpha is the last qfloat16 read.

For formats where multiple channels are packed into a single unit, the QPixelFormat::AtBeginning and QPixelFormat::AtEnd values map to the most significant and least significant bits of the packed unit, with respect to the format's own byteOrder().

For example, for QImage::Format_ARGB32, which has a type interpretation of QPixelFormat::UnsignedInteger and a byteOrder() that always matches the host system, the alpha position of QPixelFormat::AtBeginning means that the alpha can always be found at 0xFF000000.

If the pixel format and host endianness does not match care must be taken to correctly map the pixel format layout to the host memory layout.

See also alphaUsage(), alphaSize(), and premultiplied().

[constexpr noexcept] uchar QPixelFormat::alphaSize() const

Accessor function for the alpha channel size.

[constexpr noexcept] QPixelFormat::AlphaUsage QPixelFormat::alphaUsage() const

Accessor function for whether the alpha channel is used or not.

Sometimes the pixel format reserves place for an alpha channel, so alphaSize() will return > 0, but the alpha channel is not used/ignored.

For example, for QImage::Format_RGB32, the bitsPerPixel() is 32, because the alpha channel has a size of 8, but alphaUsage() reflects QPixelFormat::IgnoresAlpha.

Note that in such situations the position of the unused alpha channel is still important, as it affects the placement of the color channels.

See also alphaPosition(), alphaSize(), and premultiplied().

[constexpr noexcept] uchar QPixelFormat::bitsPerPixel() const

Accessor function for the bits used per pixel. This function returns the sum of all the color channels + the size of the alpha channel.

[constexpr noexcept] uchar QPixelFormat::blackSize() const

Accessor function for the black/key color channel.

[constexpr noexcept] uchar QPixelFormat::blueSize() const

Accessor function for the size of the blue color channel.

[constexpr noexcept] uchar QPixelFormat::brightnessSize() const

Accessor function for the brightness channel size.

[constexpr noexcept] QPixelFormat::ByteOrder QPixelFormat::byteOrder() const

The byte order of the pixel format determines the memory layout of the individual type units, as described by the typeInterpretation().

This function will never return QPixelFormat::CurrentSystemEndian as this value is translated to the system's endian value in the constructor.

For pixel formats with typeInterpretation() QPixelFormat::UnsignedByte this will typically be QPixelFormat::BigEndian, while other type interpretations will typically reflect the endianness of the current system.

If the byte order of the pixel format matches the current system the individual type units can be read and manipulated using the same bit masks and operations, regardless of the host system endianness. For example, with QImage::Format_ARGB32, which has a QPixelFormat::UnsignedInteger type interpretation, the alpha can always be read by masking the unsigned int by 0xFF000000, regardless of the host endianness.

If the pixel format and host endianness does not match care must be taken to account for this. Classes like QImage do not swap the internal bits to match the host system endianness in these cases.

See also typeInterpretation() and alphaPosition().

[constexpr noexcept] uchar QPixelFormat::channelCount() const

Accessor function for the channel count.

The channel count represents channels (color and alpha) with a size > 0.

[constexpr noexcept] QPixelFormat::ColorModel QPixelFormat::colorModel() const

Accessor function for the color model.

Note that for QPixelFormat::YUV the individual macro pixels can not be described. Instead a list of YUV formats is provided, and the bitsPerPixel() value is deduced from the YUV layout.

[constexpr noexcept] uchar QPixelFormat::cyanSize() const

Accessor function for the cyan color channel.

[constexpr noexcept] uchar QPixelFormat::greenSize() const

Accessor function for the size of the green color channel.

[constexpr noexcept] uchar QPixelFormat::hueSize() const

Accessor function for the hue channel size.

[constexpr noexcept] uchar QPixelFormat::lightnessSize() const

Accessor function for the lightness channel size.

[constexpr noexcept] uchar QPixelFormat::magentaSize() const

Accessor function for the megenta color channel.

[constexpr noexcept] QPixelFormat::AlphaPremultiplied QPixelFormat::premultiplied() const

Accessor function for the whether the alpha channel is multiplied in to the color channels.

[constexpr noexcept] uchar QPixelFormat::redSize() const

Accessor function for the size of the red color channel.

[constexpr noexcept] uchar QPixelFormat::saturationSize() const

Accessor function for the saturation channel size.

[constexpr noexcept] QPixelFormat::TypeInterpretation QPixelFormat::typeInterpretation() const

The type interpretation determines how each pixel should be read.

Each pixel is represented as one or more units of the given type, laid out sequentially in memory.

For example, QImage::Format_Mono has a pixel format of 1 bits per pixel and a QPixelFormat::UnsignedByte type interpretation, which should be read as a single byte. Similarly, QImage::Format_RGB888 has a pixel format of 24 bits per pixel, and and a QPixelFormat::UnsignedByte type interpretation, which should be read as three consecutive bytes.

Many of the QImage formats are 32-bit with a type interpretation of QPixelFormat::UnsignedInteger, which should be read as a single unsigned int.

For QPixelFormat::FloatingPoint formats like QImage::Format_RGBA16FPx4 or QImage::Format_RGBA32FPx4 the type is determined based on the size of the individual color/alpha channels, with qfloat16 for 16-bit half-float formats and float for 32-bit full-float formats.

See also byteOrder().

[constexpr noexcept] uchar QPixelFormat::yellowSize() const

Accessor function for the yellow color channel.

[constexpr noexcept] QPixelFormat::YUVLayout QPixelFormat::yuvLayout() const

Accessor function for the YUVLayout. It is difficult to describe the color channels of a YUV pixel format since YUV color model uses macro pixels. Instead the layout of the pixels are stored as an enum.