#include <Magnum/ImageView.h>
template<UnsignedInt dimensions, class T>
ImageView class
Image view.
Contents
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::
Basic usage
Usually, the view is created on some pre-existing data array in order to describe its layout, with pixel format being one of the values from the generic PixelFormat:
ImageView2D image{PixelFormat::RGBA8Unorm, {512, 256}, data};
On construction, the image view internally calculates pixel size corresponding to given pixel format using pixelSize(). This value is needed to check that the passed data array is large enough and is also required by most image manipulation operations.
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 ...
It's possible to have views on image sub-rectangles, 3D texture slices or images with over-aligned rows by passing a particular PixelStorage as first parameter. In the following snippet, the view is the center 25x25 sub-rectangle of a 75x75 8-bit RGB image , with rows aligned to four bytes:
ImageView2D image{ PixelStorage{} .setRowLength(75) .setAlignment(4) .setSkip({25, 25, 0}), PixelFormat::RGBA8Unorm, {25, 25}, data};
Data mutability
When using types derived from BasicImageView (e.g. ImageView2D), the viewed data are immutable. This is the most common use case. In order to be able to mutate the underlying data (for example in order to read into a pre-allocated memory), use BasicMutableImageView (e.g. MutableImageView2D) instead. Image and Trade::
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::
ImageView2D image{GL::PixelFormat::DepthComponent, GL::PixelType::UnsignedInt, {512, 256}, data};
In such cases, pixel size is calculated using either pixelSize(T, U)
or pixelSize(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>(image.format()); auto type = GLenum(image.formatExtra());
As a final fallback, types for which the pixelSize()
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) explicit noexcept - Constructor.
-
ImageView(PixelFormat format,
const VectorTypeFor<dimensions, Int>& size,
Containers::
ArrayView<ErasedType> data) explicit noexcept - Constructor.
- ImageView(PixelStorage storage, PixelFormat format, const VectorTypeFor<dimensions, Int>& size) explicit noexcept
- Construct an empty view.
- ImageView(PixelFormat format, const VectorTypeFor<dimensions, Int>& size) explicit noexcept
- Construct an empty view.
-
ImageView(PixelStorage storage,
UnsignedInt format,
UnsignedInt formatExtra,
UnsignedInt pixelSize,
const VectorTypeFor<dimensions, Int>& size,
Containers::
ArrayView<ErasedType> data) 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) explicit noexcept - ImageView(PixelStorage storage, UnsignedInt format, UnsignedInt formatExtra, UnsignedInt pixelSize, const VectorTypeFor<dimensions, Int>& size) 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) explicit noexcept
-
template<class U, class V>ImageView(PixelStorage storage, U format, V formatExtra, const VectorTypeFor<dimensions, Int>& size, Containers::
ArrayView<ErasedType> data) 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) 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) 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) 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) explicit noexcept
- Construct an empty view with implementation-specific pixel format.
-
template<class U>ImageView(PixelStorage storage, U format, const VectorTypeFor<dimensions, Int>& size) 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) explicit noexcept
- Construct an empty view with implementation-specific pixel format.
-
template<class U>ImageView(U format, const VectorTypeFor<dimensions, Int>& size) explicit noexcept
- Construct an empty view with implementation-specific pixel format.
-
template<UnsignedInt otherDimensions, class = typename std::ImageView(const ImageView<otherDimensions, T>& other) noexcept new in 2019.10
enable_if<(otherDimensions <dimensions)>::type> - Construct from a view of lower dimension count.
-
template<class U, class = typename std::ImageView(const ImageView<dimensions, U>& other) noexcept new in 2019.10
enable_if<std:: is_const<T>::value&& !std:: is_const<U>::value>::type> - Convert a mutable view to a const one.
Public functions
- 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
- Pixel size (in bytes)
- auto size() const -> VectorTypeFor<dimensions, Int> constexpr
- Image size.
-
auto dataProperties() const -> std::
pair<VectorTypeFor<dimensions, std:: size_t>, VectorTypeFor<dimensions, std:: size_t>> - Image data properties.
-
auto data() const -> Containers::
ArrayView<Type> - 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 - View on 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 - View on pixel data with a concrete pixel 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) explicit noexcept
Constructor.
Parameters | |
---|---|
storage | Storage of pixel data |
format | Format of pixel data |
size | Image size |
data | Image data |
The data
array is expected to be of proper size for given parameters.
template<UnsignedInt dimensions, class T>
Magnum:: ImageView<dimensions, T>:: ImageView(PixelFormat format,
const VectorTypeFor<dimensions, Int>& size,
Containers:: ArrayView<ErasedType> data) explicit noexcept
Constructor.
Parameters | |
---|---|
format | Format of pixel data |
size | Image size |
data | Image data |
Equivalent to calling ImageView(PixelStorage, PixelFormat, const VectorTypeFor<dimensions, Int>&, Containers::
template<UnsignedInt dimensions, class T>
Magnum:: ImageView<dimensions, T>:: ImageView(PixelStorage storage,
PixelFormat format,
const VectorTypeFor<dimensions, Int>& size) explicit noexcept
Construct an empty view.
Parameters | |
---|---|
storage | Storage of pixel data |
format | Format of pixel data |
size | Image size |
Data pointer is set to nullptr
, call setData() to assign a memory view to the image.
template<UnsignedInt dimensions, class T>
Magnum:: ImageView<dimensions, T>:: ImageView(PixelFormat format,
const VectorTypeFor<dimensions, Int>& size) explicit noexcept
Construct an empty view.
Parameters | |
---|---|
format | Format of pixel data |
size | Image size |
Equivalent to calling ImageView(PixelStorage, PixelFormat, const VectorTypeFor<dimensions, Int>&) 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) 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 |
size | Image size |
data | Image data |
Unlike with ImageView(PixelStorage, PixelFormat, const VectorTypeFor<dimensions, Int>&, Containers::format
in PixelFormat.
The data
array is expected to be of proper size for given parameters.
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) 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) 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 |
size | Image size |
Unlike with ImageView(PixelStorage, PixelFormat, const VectorTypeFor<dimensions, Int>&), where pixel size is calculated automatically using pixelSize(PixelFormat), 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.
template<UnsignedInt dimensions, class T>
Magnum:: ImageView<dimensions, T>:: ImageView(PixelStorage storage,
PixelFormat format,
UnsignedInt formatExtra,
UnsignedInt pixelSize,
const VectorTypeFor<dimensions, Int>& size) 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) 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 |
Uses ADL to find a corresponding pixelSize(T, U)
overload, then calls ImageView(PixelStorage, UnsignedInt, UnsignedInt, UnsignedInt, const VectorTypeFor<dimensions, Int>&, Containers::
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) 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 |
Uses ADL to find a corresponding pixelSize(T)
overload, then calls ImageView(PixelStorage, UnsignedInt, UnsignedInt, UnsignedInt, const VectorTypeFor<dimensions, Int>&, Containers::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) 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 |
Equivalent to calling ImageView(PixelStorage, U, V, const VectorTypeFor<dimensions, Int>&, Containers::
template<UnsignedInt dimensions, class T>
template<class U>
Magnum:: ImageView<dimensions, T>:: ImageView(U format,
const VectorTypeFor<dimensions, Int>& size,
Containers:: ArrayView<ErasedType> data) explicit noexcept
Construct an image view with implementation-specific pixel format.
Parameters | |
---|---|
format | Format of pixel data |
size | Image size |
data | Image data |
Equivalent to calling ImageView(PixelStorage, U, const VectorTypeFor<dimensions, Int>&, Containers::
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) 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 |
Uses ADL to find a corresponding pixelSize(T, U)
overload, then calls ImageView(PixelStorage, UnsignedInt, UnsignedInt, UnsignedInt, const VectorTypeFor<dimensions, Int>&) 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) 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 |
Uses ADL to find a corresponding pixelSize(T)
overload, then calls ImageView(PixelStorage, UnsignedInt, UnsignedInt, UnsignedInt, const VectorTypeFor<dimensions, Int>&) 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) 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 |
Equivalent to calling ImageView(PixelStorage, U, V, const VectorTypeFor<dimensions, Int>&, Containers::
template<UnsignedInt dimensions, class T>
template<class U>
Magnum:: ImageView<dimensions, T>:: ImageView(U format,
const VectorTypeFor<dimensions, Int>& size) explicit noexcept
Construct an empty view with implementation-specific pixel format.
Parameters | |
---|---|
format | Format of pixel data |
size | Image size |
Equivalent to calling ImageView(PixelStorage, U, const VectorTypeFor<dimensions, Int>&) with default-constructed PixelStorage.
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
Pixel size (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::
template<UnsignedInt dimensions, class T>
Containers:: ArrayView<Type> Magnum:: ImageView<dimensions, T>:: data() const
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
View on pixel data.
Provides direct and easy-to-use access to image pixels. See Obtaining a view on pixel data 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
View on pixel data with a concrete pixel 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.