Struct CGImageMetadataTag

Source

#[repr(C)]
pub struct CGImageMetadataTag { /* private fields */ }

Available on crate feature CGImageMetadata only.

Expand description

an individual metadata tag

A CGImageMetadataTag encapsulates an EXIF, IPTC, or XMP property. All tags contain a namespace, prefix, name, type, and value. Please see

 CGImageMetadataTagCreate

for more details.

Implementations§

Source §

impl CGImageMetadataTag

Source

pub unsafe fn new( xmlns: &CFString, prefix: Option<&CFString>, name: &CFString, type: CGImageMetadataType, value: &CFType, ) -> Option<CFRetained<CGImageMetadataTag>>

Creates a new CGImageMetadataTag

Parameter xmlns: The namespace for the tag. The value can be a common XMP namespace defined above, such as kCGImageMetadataNamespaceExif, or a CFString with a custom namespace URI. Custom namespaces must be a valid XML namespace. By convention, namespaces should end with either ‘/’ or ‘#’. For example, exif uses the namespace “http://ns.adobe.com/exif/1.0/”.

Parameter prefix: An abbreviation for the XML namespace. The value can be NULL if the namespace is defined as a constant. Custom prefixes must be a valid XML name. For example, the prefix used for “http://ns.adobe.com/exif/1.0/” is “exif”. The XMP serialization of the tag will use the prefix. Prefixes are also important for path-based CGImageMetadata functions, such as

 CGImageMetadataCopyStringValueWithPath

or

 CGImageMetadataSetValueWithPath

.

Parameter name: The name of the tag. It must be a valid XMP name.

Parameter type: The type of the tag’s value. Must be a constant from

  
 CGImageMetadataType

.

Parameter value: The value of the tag. Allowable CFTypes include CFStringRef, CFNumberRef, CFBooleanRef, CFArrayRef, and CFDictionaryRef. The CFType of ‘value’ must correspond to the ‘type’. The elements of a CFArray must be either a CFStringRef or CGImageMetadataTagRef. The keys of a CFDictionary must be CFStringRefs with valid XMP names. The values of a CFDictionary must be either CFStringRefs or CGImageMetadataTagRefs. A shallow copy of the value is stored in the tag. Therefore, modifying a mutable value after the tag is created will not affect the tag’s value.

Returns: Returns a pointer to a new CGImageMetadataTag. Returns NULL if a tag could not be created with the specified parameters.

Source

pub unsafe fn namespace( self: &CGImageMetadataTag, ) -> Option<CFRetained<CFString>>

*!

Returns a copy of the tag’s namespace

Source

pub unsafe fn prefix(self: &CGImageMetadataTag) -> Option<CFRetained<CFString>>

Returns a copy of the tag’s prefix

Source

pub unsafe fn name(self: &CGImageMetadataTag) -> Option<CFRetained<CFString>>

Returns a copy of the tag’s name

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pub unsafe fn value(self: &CGImageMetadataTag) -> Option<CFRetained<CFType>>

Returns a shallow copy of the tag’s value

This function should only be used to read the tag’s value. CGImageMetadataCopyTagWithPath returns a copy of the tag (including a copy of the tag’s value). Therefore mutating a tag’s value returned from this function may not actually mutate the value in the CGImageMetadata. It is recommended to create a new tag followed by CGImageMetadataSetTagWithPath, or use CGImageMetadataSetValueWithPath to mutate a metadata value.

Source

pub unsafe fn type(self: &CGImageMetadataTag) -> CGImageMetadataType

Get the type of the CGImageMetadataTag

Returns: Returns a CGImageMetadataType constant for the CGImageMetadataTag. This is primarily used to determine how to interpret the tag’s value.

Source

pub unsafe fn qualifiers( self: &CGImageMetadataTag, ) -> Option<CFRetained<CFArray>>

Return a copy of the tag’s qualifiers

XMP allows properties to contain supplemental properties called qualifiers. Qualifiers are themselves CGImageMetadataTags with their own namespace, prefix, name, and value. A common use is the xml:lang qualifier for elements of an alternate-text array.

Returns: Returns a copy of the array of qualifiers. Elements of the array are CGImageMetadataTags. Returns NULL if the tag does not have any qualifiers. The copy is shallow, the qualifiers are not deep copied.

Methods from Deref<Target = CFType>§

Source

pub fn downcast_ref<T>(&self) -> Option<&T>
where T: ConcreteType,

Attempt to downcast the type to that of type T.

This is the reference-variant. Use CFRetained::downcast if you want to convert a retained type. See also ConcreteType for more details on which types support being converted to.

Source

pub fn retain_count(&self) -> usize

Get the reference count of the object.

This function may be useful for debugging. You normally do not use this function otherwise.

Beware that some things (like CFNumbers, small CFStrings etc.) may not have a normal retain count for optimization purposes, and can return usize::MAX in that case.