#include <Magnum/ImageView.h>
template<UnsignedInt dimensions, class T>
Magnum::ImageView class

Image view.

Non-owning view on multi-dimensional image data together with layout and pixel format description. Unlike Image, this class doesn't take ownership of the data, so it is targeted for wrapping data that is either stored in stack/constant memory (and shouldn't be deleted) or is managed by something else.

This class can act as drop-in replacement for Image or Trade::ImageData, these two are additionally implicitly convertible to it. Particular graphics API wrappers provide additional image classes, for example GL::BufferImage. See also CompressedImageView for equivalent functionality targeted on compressed image formats.

Basic usage

The view is created from a PixelFormat, size in pixels and a data view:

ImageView2D view{PixelFormat::RGBA8Unorm, {512, 256}, data};

The constructor internally checks that the passed array is large enough. For performance reasons it by default expects rows aligned to four bytes, which you need to account for if using odd image sizes in combination with one-, two- or three-component formats. While the recommended way is to pad the row data to satisfy the alignment similarly as shown in Image usage docs, but with views it's more likely that you have to adapt to a layout of an existing data array by passing a PixelStorage instance with the alignment value overriden if needed:

PixelFormat format = …;
Vector2i size = …;
std::size_t rowLength = size.x()*pixelFormatSize(format);

ImageView2D view{
    PixelStorage{}.setAlignment(rowLength % 4 == 0 ? 4 : 1),
    format, size, tightlyPackedData};

It's also possible to create an empty view and assign the memory later. That is useful for example in case of multi-buffered video streaming, where each frame has the same properties but a different memory location:

ImageView2D frame{PixelFormat::RGBA8Unorm, {512, 256}};

frame.setData(evenFrameData);
// Use even frame data ...

frame.setData(oddFrameData);
// Use odd frame data ...

The PixelStorage also allows for specifying arbitrary image slices by passing appropriate row length, image height and skip parameters. In the following snippet, the view is the center 25x25 sub-rectangle of a 75x75 8-bit RGB image (with tightly packed rows again):

ImageView2D view{
    PixelStorage{}
        .setAlignment(1)
        .setRowLength(75)
        .setSkip({25, 25, 0}),
    PixelFormat::RGBA8Unorm, {25, 25}, data};

Image views provides pixel data access via pixels() in the same way as the Image class. See its documentation for more information.

Data mutability

The ImageView2D type and related one- and three-dimensional variants only provide immutable access to the referenced data, as that's the most common use case. In order to be able to modify the data (for example in order to read into a pre-allocated memory), use MutableImageView2D and friends instead. Image and Trade::ImageData are convertible to either of these. Similarly to Corrade::Containers::ArrayView etc., a mutable view is also implicitly convertible to a const one.

Implementation-specific formats

For known graphics APIs, there's a set of utility functions converting from PixelFormat to implementation-specific format identifiers and such conversion is done implicitly when passing the view to a particular API. See the enum documentation and documentation of its values for more information.

In some cases, for example when there's no corresponding generic format available, it's desirable to specify the pixel format using implementation-specific identifiers directly. In case of OpenGL that would be the GL::PixelFormat and GL::PixelType pair:

ImageView2D view{GL::PixelFormat::DepthComponent,
                 GL::PixelType::UnsignedInt, {512, 256}, data};

In such cases, pixel size is calculated using either pixelFormatSize(T, U) or pixelFormatSize(T) that is found using ADL, with T and U corresponding to types of passed arguments. The implementation-specific format is wrapped in PixelFormat using pixelFormatWrap() and format() returns the wrapped value. In order to distinguish if the format is wrapped, use isPixelFormatImplementationSpecific() and then extract the implementation-specific identifier using pixelFormatUnwrap(). For APIs that have an additional format specifier (such as OpenGL), the second value is stored verbatim in formatExtra():

auto format = pixelFormatUnwrap<GLenum>(view.format());
auto type = GLenum(view.formatExtra());

As a final fallback, types for which the pixelFormatSize() overload is not available can be specified directly together with pixel size. In particular, pixel size of 0 will cause the image to be treated as fully opaque data, disabling all slicing operations. The following shows a image view using Metal-specific format identifier:

/* Default pixel storage, 8-bit sRGB + alpha, four bytes per pixel */
ImageView2D view{{}, MTLPixelFormatRGBA8Unorm_sRGB, {}, 4, {256, 256}, data};

Public types

enum (anonymous): UnsignedInt { Dimensions = dimensions }
using Type = T
Raw data type.
using ErasedType = std::conditional<std::is_const<T>::value, const void, void>::type
Erased data type.

Constructors, destructors, conversion operators

ImageView(PixelStorage storage, PixelFormat format, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept
Constructor.
ImageView(PixelFormat format, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept
Constructor.
ImageView(PixelStorage storage, PixelFormat format, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an empty view.
ImageView(PixelFormat format, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an empty view.
ImageView(PixelStorage storage, UnsignedInt format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an image view with implementation-specific pixel format.
ImageView(PixelStorage storage, PixelFormat format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept
ImageView(PixelStorage storage, UnsignedInt format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an empty view with implementation-specific pixel format.
ImageView(PixelStorage storage, PixelFormat format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept
template<class U, class V>
ImageView(PixelStorage storage, U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an image view with implementation-specific pixel format.
template<class U>
ImageView(PixelStorage storage, U format, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an image view with implementation-specific pixel format.
template<class U, class V>
ImageView(U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an image view with implementation-specific pixel format.
template<class U>
ImageView(U format, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an image view with implementation-specific pixel format.
template<class U, class V>
ImageView(PixelStorage storage, U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an empty view with implementation-specific pixel format.
template<class U>
ImageView(PixelStorage storage, U format, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an empty view with implementation-specific pixel format.
template<class U, class V>
ImageView(U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an empty view with implementation-specific pixel format.
template<class U>
ImageView(U format, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept
Construct an empty view with implementation-specific pixel format.
template<UnsignedInt otherDimensions, class = typename std::enable_if<(otherDimensions <dimensions)>::type>
ImageView(const ImageView<otherDimensions, T>& other, ImageFlags<dimensions> flags = {}) noexcept new in 2019.10
Construct from a view of lower dimension count.
template<class U, class = typename std::enable_if<std::is_const<T>::value&& !std::is_const<U>::value>::type>
ImageView(const ImageView<dimensions, U>& other) noexcept new in 2019.10
Convert a mutable view to a const one.

Public functions

auto flags() const -> ImageFlags<dimensions> new in Git master
Layout flags.
auto storage() const -> PixelStorage
Storage of pixel data.
auto format() const -> PixelFormat
Format of pixel data.
auto formatExtra() const -> UnsignedInt
Additional pixel format specifier.
auto pixelSize() const -> UnsignedInt
Size of a pixel in bytes.
auto size() const -> const VectorTypeFor<dimensions, Int>& constexpr
Image size in pixels.
auto dataProperties() const -> std::pair<VectorTypeFor<dimensions, std::size_t>, VectorTypeFor<dimensions, std::size_t>>
Image data properties.
auto data() const -> Containers::ArrayView<Type>
Raw image data.
template<class U>
auto data() const -> const U* deprecated in 2019.10
Image data in a particular type.
void setData(Containers::ArrayView<ErasedType> data)
Set image data.
auto pixels() const -> Containers::StridedArrayView<dimensions+1, Type> new in 2019.10
Pixel data.
template<class U>
auto pixels() const -> Containers::StridedArrayView<dimensions, typename std::conditional<std::is_const<Type>::value, typename std::add_const<U>::type, U>::type> new in 2019.10
Pixel data in a concrete type.

Enum documentation

template<UnsignedInt dimensions, class T>
enum Magnum::ImageView<dimensions, T>::(anonymous): UnsignedInt

Enumerators
Dimensions

Image dimension count

Typedef documentation

template<UnsignedInt dimensions, class T>
typedef T Magnum::ImageView<dimensions, T>::Type

Raw data type.

const char for BasicImageView and char for BasicMutableImageView. See also ErasedType.

template<UnsignedInt dimensions, class T>
typedef std::conditional<std::is_const<T>::value, const void, void>::type Magnum::ImageView<dimensions, T>::ErasedType

Erased data type.

const void for BasicImageView and const void for BasicMutableImageView. See also Type.

Function documentation

template<UnsignedInt dimensions, class T>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, PixelFormat format, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept

Constructor.

Parameters
storage Storage of pixel data
format Format of pixel data
size Image size
data Image data
flags Image layout flags

The data array is expected to be of proper size for given parameters. For a 3D image, if flags contain ImageFlag3D::CubeMap, the size is expected to match its restrictions.

template<UnsignedInt dimensions, class T>
Magnum::ImageView<dimensions, T>::ImageView(PixelFormat format, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept

Constructor.

Parameters
format Format of pixel data
size Image size
data Image data
flags Image layout flags

Equivalent to calling ImageView(PixelStorage, PixelFormat, const VectorTypeFor<dimensions, Int>&, Containers::ArrayView<ErasedType>, ImageFlags<dimensions>) with default-constructed PixelStorage.

template<UnsignedInt dimensions, class T>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, PixelFormat format, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an empty view.

Parameters
storage Storage of pixel data
format Format of pixel data
size Image size
flags Image layout flags

Data pointer is set to nullptr, call setData() to assign a memory view to the image. For a 3D image, if flags contain ImageFlag3D::CubeMap, the size is expected to match its restrictions.

template<UnsignedInt dimensions, class T>
Magnum::ImageView<dimensions, T>::ImageView(PixelFormat format, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an empty view.

Parameters
format Format of pixel data
size Image size
flags Image layout flags

Equivalent to calling ImageView(PixelStorage, PixelFormat, const VectorTypeFor<dimensions, Int>&, ImageFlags<dimensions>) with default-constructed PixelStorage.

template<UnsignedInt dimensions, class T>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, UnsignedInt format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an image view with implementation-specific pixel format.

Parameters
storage Storage of pixel data
format Format of pixel data
formatExtra Additional pixel format specifier
pixelSize Size of a pixel in given format, in bytes
size Image size, in pixels
data Image data
flags Image layout flags

Unlike with ImageView(PixelStorage, PixelFormat, const VectorTypeFor<dimensions, Int>&, Containers::ArrayView<ErasedType>, ImageFlags<dimensions>), where pixel size is calculated automatically using pixelFormatSize(), this allows you to specify an implementation-specific pixel format and pixel size directly. Uses pixelFormatWrap() internally to wrap format in PixelFormat.

The data array is expected to be of proper size for given parameters. For a 3D image, if flags contain ImageFlag3D::CubeMap, the size is expected to match its restrictions.

template<UnsignedInt dimensions, class T>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, PixelFormat format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Equivalent to the above for format already wrapped with pixelFormatWrap().

template<UnsignedInt dimensions, class T>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, UnsignedInt format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an empty view with implementation-specific pixel format.

Parameters
storage Storage of pixel data
format Format of pixel data
formatExtra Additional pixel format specifier
pixelSize Size of a pixel in given format, in bytes
size Image size, in pixels
flags Image layout flags

Unlike with ImageView(PixelStorage, PixelFormat, const VectorTypeFor<dimensions, Int>&, ImageFlags<dimensions>), where pixel size is calculated automatically using pixelFormatSize(), this allows you to specify an implementation-specific pixel format and pixel size directly. Uses pixelFormatWrap() internally to wrap format in PixelFormat.

Data pointer is set to nullptr, call setData() to assign a memory view to the image. For a 3D image, if flags contain ImageFlag3D::CubeMap, the size is expected to match its restrictions.

template<UnsignedInt dimensions, class T>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, PixelFormat format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Equivalent to the above for format already wrapped with pixelFormatWrap().

template<UnsignedInt dimensions, class T> template<class U, class V>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an image view with implementation-specific pixel format.

Parameters
storage Storage of pixel data
format Format of pixel data
formatExtra Additional pixel format specifier
size Image size
data Image data
flags Image layout flags

Uses ADL to find a corresponding pixelFormatSize(T, U) overload, then calls ImageView(PixelStorage, UnsignedInt, UnsignedInt, UnsignedInt, const VectorTypeFor<dimensions, Int>&, Containers::ArrayView<ErasedType>, ImageFlags<dimensions>) with calculated pixel size.

template<UnsignedInt dimensions, class T> template<class U>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, U format, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an image view with implementation-specific pixel format.

Parameters
storage Storage of pixel data
format Format of pixel data
size Image size
data Image data
flags Image layout flags

Uses ADL to find a corresponding pixelFormatSize(T) overload, then calls ImageView(PixelStorage, UnsignedInt, UnsignedInt, UnsignedInt, const VectorTypeFor<dimensions, Int>&, Containers::ArrayView<ErasedType>, ImageFlags<dimensions>) with calculated pixel size and formatExtra set to 0.

template<UnsignedInt dimensions, class T> template<class U, class V>
Magnum::ImageView<dimensions, T>::ImageView(U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an image view with implementation-specific pixel format.

Parameters
format Format of pixel data
formatExtra Additional pixel format specifier
size Image size
data Image data
flags Image layout flags

Equivalent to calling ImageView(PixelStorage, U, V, const VectorTypeFor<dimensions, Int>&, Containers::ArrayView<ErasedType>, ImageFlags<dimensions>) with default-constructed PixelStorage.

template<UnsignedInt dimensions, class T> template<class U>
Magnum::ImageView<dimensions, T>::ImageView(U format, const VectorTypeFor<dimensions, Int>& size, Containers::ArrayView<ErasedType> data, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an image view with implementation-specific pixel format.

Parameters
format Format of pixel data
size Image size
data Image data
flags Image layout flags

Equivalent to calling ImageView(PixelStorage, U, const VectorTypeFor<dimensions, Int>&, Containers::ArrayView<ErasedType>, ImageFlags<dimensions>) with default-constructed PixelStorage.

template<UnsignedInt dimensions, class T> template<class U, class V>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an empty view with implementation-specific pixel format.

Parameters
storage Storage of pixel data
format Format of pixel data
formatExtra Additional pixel format specifier
size Image size
flags Image layout flags

Uses ADL to find a corresponding pixelFormatSize(T, U) overload, then calls ImageView(PixelStorage, UnsignedInt, UnsignedInt, UnsignedInt, const VectorTypeFor<dimensions, Int>&, ImageFlags<dimensions>) with calculated pixel size.

Data pointer is set to nullptr, call setData() to assign a memory view to the image.

template<UnsignedInt dimensions, class T> template<class U>
Magnum::ImageView<dimensions, T>::ImageView(PixelStorage storage, U format, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an empty view with implementation-specific pixel format.

Parameters
storage Storage of pixel data
format Format of pixel data
size Image size
flags Image layout flags

Uses ADL to find a corresponding pixelFormatSize(T) overload, then calls ImageView(PixelStorage, UnsignedInt, UnsignedInt, UnsignedInt, const VectorTypeFor<dimensions, Int>&, ImageFlags<dimensions>) with calculated pixel size and formatExtra set to 0.

Data pointer is set to nullptr, call setData() to assign a memory view to the image.

template<UnsignedInt dimensions, class T> template<class U, class V>
Magnum::ImageView<dimensions, T>::ImageView(U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an empty view with implementation-specific pixel format.

Parameters
format Format of pixel data
formatExtra Additional pixel format specifier
size Image size
flags Image layout flags

Equivalent to calling ImageView(PixelStorage, U, V, const VectorTypeFor<dimensions, Int>&, Containers::ArrayView<ErasedType>, ImageFlags<dimensions>) with default-constructed PixelStorage.

template<UnsignedInt dimensions, class T> template<class U>
Magnum::ImageView<dimensions, T>::ImageView(U format, const VectorTypeFor<dimensions, Int>& size, ImageFlags<dimensions> flags = {}) explicit noexcept

Construct an empty view with implementation-specific pixel format.

Parameters
format Format of pixel data
size Image size
flags Image layout flags

Equivalent to calling ImageView(PixelStorage, U, const VectorTypeFor<dimensions, Int>&, ImageFlags<dimensions>) with default-constructed PixelStorage.

template<UnsignedInt dimensions, class T> template<UnsignedInt otherDimensions, class = typename std::enable_if<(otherDimensions <dimensions)>::type>
Magnum::ImageView<dimensions, T>::ImageView(const ImageView<otherDimensions, T>& other, ImageFlags<dimensions> flags = {}) noexcept new in 2019.10

Construct from a view of lower dimension count.

Size in the new dimension(s) is set to 1. Original image flags are preserved, except for ImageFlag2D::Array when constructing a 3D image from a 2D image (i.e., a 1D array image), as there's no concept of 2D arrays of 1D images. Use the flags parameter to add arbitrary other flags.

template<UnsignedInt dimensions, class T>
PixelFormat Magnum::ImageView<dimensions, T>::format() const

Format of pixel data.

Returns either a defined value from the PixelFormat enum or a wrapped implementation-specific value. Use isPixelFormatImplementationSpecific() to distinguish the case and pixelFormatUnwrap() to extract an implementation-specific value, if needed.

template<UnsignedInt dimensions, class T>
UnsignedInt Magnum::ImageView<dimensions, T>::formatExtra() const

Additional pixel format specifier.

Some implementations (such as OpenGL) define a pixel format using two values. This field contains the second implementation-specific value verbatim, if any. See format() for more information.

template<UnsignedInt dimensions, class T>
UnsignedInt Magnum::ImageView<dimensions, T>::pixelSize() const

Size of a pixel in bytes.

template<UnsignedInt dimensions, class T>
std::pair<VectorTypeFor<dimensions, std::size_t>, VectorTypeFor<dimensions, std::size_t>> Magnum::ImageView<dimensions, T>::dataProperties() const

Image data properties.

See PixelStorage::dataProperties() for more information.

template<UnsignedInt dimensions, class T>
Containers::ArrayView<Type> Magnum::ImageView<dimensions, T>::data() const

Raw image data.

template<UnsignedInt dimensions, class T> template<class U>
const U* Magnum::ImageView<dimensions, T>::data() const

Image data in a particular type.

template<UnsignedInt dimensions, class T>
void Magnum::ImageView<dimensions, T>::setData(Containers::ArrayView<ErasedType> data)

Set image data.

The data array is expected to be of proper size for parameters specified in the constructor.

template<UnsignedInt dimensions, class T>
Containers::StridedArrayView<dimensions+1, Type> Magnum::ImageView<dimensions, T>::pixels() const new in 2019.10

Pixel data.

Provides direct and easy-to-use access to image pixels. See Pixel data access for more information. If the view is empty (with data() being nullptr), returns nullptr as well.

template<UnsignedInt dimensions, class T> template<class U>
Containers::StridedArrayView<dimensions, typename std::conditional<std::is_const<Type>::value, typename std::add_const<U>::type, U>::type> Magnum::ImageView<dimensions, T>::pixels() const new in 2019.10

Pixel data in a concrete type.

Compared to non-templated pixels() in addition casts the pixel data to a specified type. The user is responsible for choosing correct type for given format() — checking it on the library side is not possible for the general case. If the view is empty (with data() being nullptr), returns nullptr as well. See also Pixel data access for more information.