Xmp Lua Reference Documentation
chilkat.Xmp
Current Version: 11.7.0
Markdown version of this page for AI tools (v 11.7.0) · all AI docs
Chilkat.Xmp
Load a
Retrieve embedded XMP documents as
Add or update namespace-qualified string and integer properties such as
Work with XMP arrays such as
Use built-in namespace mappings or add custom namespace-to-URI mappings
for application-specific XMP properties.
Remove properties, arrays, structures, or embedded XMP documents, then
persist changes to a file or return the updated image as a byte buffer.
Read, modify, add, remove, and save XMP metadata in JPG and TIFF files.
Chilkat.Xmp is a legacy class for working with embedded XMP
metadata in JPG and TIFF image files. It can load
image files or image data from memory, locate embedded XMP documents, return
XMP metadata as Chilkat.Xml, create new XMP documents, add or
update simple string and integer properties, manage arrays and structured
properties, add namespace mappings, remove selected XMP properties or entire
embedded XMP documents, and save the updated image back to a file or byte
buffer.
Chilkat.Xmp is maintained for existing JPG/TIFF XMP workflows,
but it is not planned to be extended to support additional file types.
Load JPG or TIFF metadata
JPG or TIFF file from disk or memory and
inspect how many embedded XMP documents were found.
Access XMP as XML
Chilkat.Xml objects for
inspection, editing, or direct XML-level processing.
Add simple properties
dc:subject, photoshop:Credit, or
tiff:XResolution.
Arrays and structures
bag, seq, and
alt, and manage structured property values.
Namespaces
Remove and save
LoadAppFile or
LoadFromBuffer, retrieve an embedded XMP document with
GetEmbedded or create one with NewXmp, modify it
using the add/remove property methods, then call SaveAppFile or
SaveToBuffer to persist the updated image metadata.
SaveAppFile is called. For memory workflows, use
SaveToBuffer to obtain the updated JPG or TIFF bytes.
Object Creation
local chilkat = require("chilkat")
local xmp = chilkat.Xmp.new()Creates the object (chilkat.Xmp() does the same). Lua's garbage collector frees it when it is no longer referenced; xmp:dispose() frees it at once, and in Lua 5.4 and later local xmp <close> = chilkat.Xmp.new() frees it when the block ends. Calling a method of a disposed object raises an error.
Errors
A method that fails returns nil followed by the error text, as io.open does: local body, err = xmp:method(...), where err is the object's last_error_text. Wrap the call in assert() to raise an error with that text instead. Methods that answer a question return true or false, numbers are returned as they are (check last_method_success where the description says a value means failure), and property reads and writes never fail for Chilkat reasons.
Misuse raises a Lua error: a wrong argument type or a missing argument (bad argument #1 to ...), an unknown property name, a write to a read-only property, an out-of-range integer, or an object of the wrong class.
Names are Chilkat's in snake_case: QuickGetStr is quick_get_str, LastErrorText is last_error_text. Properties are fields (xmp.verbose_logging = true) and methods use the colon (xmp:method(...)). Strings are UTF-8; binary data is a Lua string of bytes. Indexes are 0-based, as in every Chilkat API. Unlocking: call chilkat.unlock_bundle("...") once at startup.
Properties
DebugLogFilePath
local strVal = xmp.debug_log_file_path
xmp.debug_log_file_path = strVal
If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.
Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.
Possible causes of hangs include:
- A timeout property set to 0, indicating an infinite timeout.
- A hang occurring within an event callback in the application code.
- An internal bug in the Chilkat code causing the hang.
LastErrorHtml
local strVal = xmp.last_error_html
Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastErrorText
local strVal = xmp.last_error_text
Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
LastErrorXml
local strVal = xmp.last_error_xml
Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastMethodSuccess
local boolVal = xmp.last_method_success
xmp.last_method_success = boolVal
Indicates the success or failure of the most recent method call: true means success, false means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.
NumEmbedded
local intVal = xmp.num_embedded
The number of XMP metadata documents found within the JPG or TIFF file loaded by LoadAppFile.
topStructInnerDescrip
local boolVal = xmp.struct_inner_descrip
xmp.struct_inner_descrip = boolVal
Determines whether structures are stored with rdf:parseType=Resource, or within an rdf:Description sub-node.
UncommonOptions
local strVal = xmp.uncommon_options
xmp.uncommon_options = strVal
A property to be used for future uncommon needs. The default value is the empty string.
topVerboseLogging
local boolVal = xmp.verbose_logging
xmp.verbose_logging = boolVal
If set to true, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is false. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
Version
local strVal = xmp.version
Methods
AddArray
-- arr_type is a string
-- prop_name is a string
-- values is a chilkat.StringArray
-- ok is true, or nil and err on failure
local ok, err = xmp:add_array(xml, arr_type, prop_name, values)
Adds or replaces an XMP property array. The XMP metadata to be updated is contained in the XML object passed in the 1st argument. The 2nd argument specifies the array type, which can be bag, seq, or alt. The property name should be prefixed with the namespace, such as dc:subject.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
AddNsMapping
-- uri is a string
xmp:add_ns_mapping(ns, uri)
Adds a namespace to URI mapping. When a property is added via AddSimpleString or any of the other methods, the property name is namespace qualified. When adding the first property in a namespace, the rdf:Description is automatically added and the URI is obtained from the namespace-to-URI mappings. The standard (and commonly used) namespace mappings are defined by default. This is only used if the namespace is custom or not already handled.
topAddSimpleInt
-- prop_name is a string
-- prop_val is an integer
-- ok is true, or nil and err on failure
local ok, err = xmp:add_simple_int(i_xml, prop_name, prop_val)
Adds or updates an XMP integer property. The XMP metadata to be updated is contained in the XML object passed in the 1st argument. The property name should be prefixed with the namespace, such as tiff:XResolution.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
AddSimpleStr
-- prop_name is a string
-- prop_val is a string
-- ok is true, or nil and err on failure
local ok, err = xmp:add_simple_str(i_xml, prop_name, prop_val)
Adds or updates a simple XMP string property. The XMP metadata to be updated is contained in the XML object passed in the 1st argument. The property name should be prefixed with the namespace, such as photoshop:Credit.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
AddStructProp
-- struct_name is a string
-- prop_name is a string
-- prop_value is a string
-- ok is true, or nil and err on failure
local ok, err = xmp:add_struct_prop(i_chilkat_xml, struct_name, prop_name, prop_value)
Adds or updates an XMP structured property value. The XMP metadata to be updated is contained in the XML object passed in the 1st argument. The structure name should be prefixed with the namespace, such as Iptc4xmpCore:CreatorContactInfo. The property name within the structure should also be prefixed with the namespace, such as Iptc4xmpCore:CiAdrCity.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
Append
-- ok is true, or nil and err on failure
local ok, err = xmp:append(i_xml)
Appends a new XMP metadata file to the XMP object. Any XMPs appended via this method will be present in the file when SaveAppFile is called. Files containing XMP metadata typically only include a single XMP document, so this method is usually only called when adding XMP metadata to a file for the first time.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GetArray
-- prop_name is a string
-- string_array is a chilkat.StringArray, or nil and err on failure
local string_array, err = xmp:get_array(i_xml, prop_name)
Finds and returns an XMP array property. The property name should be prefixed with the namespace, such as dc:subject.
Returns a new object, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead. The returned object is independent of this one.
GetEmbedded
-- xml is a chilkat.Xml, or nil and err on failure
local xml, err = xmp:get_embedded(index)
Returns the Nth embedded XMP document as a Chilkat XML object.
Returns a new object, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead. The returned object is independent of this one.
GetProperty
-- prop_name is a string
-- xml is a chilkat.Xml, or nil and err on failure
local xml, err = xmp:get_property(i_xml, prop_name)
To be documented soon...
Returns a new object, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead. The returned object is independent of this one.
GetSimpleInt
-- prop_name is a string
-- n is an integer
local n = xmp:get_simple_int(i_xml, prop_name)
Finds and returns an XMP integer property. The property name should be prefixed with the namespace, such as tiff:ResolutionUnit.
GetSimpleStr
-- prop_name is a string
-- str is a string, or nil and err on failure
local str, err = xmp:get_simple_str(i_xml, prop_name)
Finds and returns an XMP simple string property. The property name should be prefixed with the namespace, such as photoshop:Source.
Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
GetStructPropNames
-- struct_name is a string
-- string_array is a chilkat.StringArray, or nil and err on failure
local string_array, err = xmp:get_struct_prop_names(i_xml, struct_name)
Returns the property names used by an exsting structure within an XMP document. The contents of the structure can be retrieved by calling GetStructValue for each property name returned by GetStructPropNames.
Returns a new object, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead. The returned object is independent of this one.
GetStructValue
-- struct_name is a string
-- prop_name is a string
-- str is a string, or nil and err on failure
local str, err = xmp:get_struct_value(i_xml, struct_name, prop_name)
Returns the value of a single item within an XMP structure property. Property names should always be prefixed with the namespace.
Returns the string, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
LoadAppFile
-- ok is true, or nil and err on failure
local ok, err = xmp:load_app_file(filename)
Loads a TIFF or JPG file into the XMP object.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
NewXmp
Creates and returns a new/empty XMP metadata document as a Chilkat XML object.
Returns a new object, or nil, err on failure (or when nothing is found). The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead. The returned object is independent of this one.
RemoveAllEmbedded
local ok, err = xmp:remove_all_embedded()
Removes all XMP metadata documents from an XMP object. After calling this method, call SaveAppFile to rewrite the JPG or TIFF file with the XMP metadata removed.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
RemoveArray
-- prop_name is a string
-- ok is true, or nil and err on failure
local ok, err = xmp:remove_array(i_xml, prop_name)
Removes an XMP array property from the XMP document.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
RemoveEmbedded
-- ok is true, or nil and err on failure
local ok, err = xmp:remove_embedded(index)
Removes a single XMP metadata document from the JPG or TIFF file. Call SaveAppFile to persist the changes to disk.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
RemoveNsMapping
xmp:remove_ns_mapping(ns)
Removes a namespace-to-URI mapping.
topRemoveSimple
-- prop_name is a string
-- ok is true, or nil and err on failure
local ok, err = xmp:remove_simple(i_xml, prop_name)
Removes a simple XMP property from the XMP document.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
RemoveStruct
-- struct_name is a string
-- ok is true, or nil and err on failure
local ok, err = xmp:remove_struct(i_xml, struct_name)
Removes an XMP structure property from the XMP document.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
RemoveStructProp
-- struct_name is a string
-- prop_name is a string
-- ok is true, or nil and err on failure
local ok, err = xmp:remove_struct_prop(i_xml, struct_name, prop_name)
Removes a single member from an XMP structured property.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.
SaveAppFile
-- ok is true, or nil and err on failure
local ok, err = xmp:save_app_file(filename)
Persists all changes made to the XMP document(s) by saving the XMP object to a file. Changes made by adding, updating, or removing properties are not persisted to the filesystem until this is called.
Returns true on success, nil, err on failure. The second return value, err, is the object's last_error_text; wrap the call in assert() to raise an error instead.