Class: Vips::Operation

Inherits:
Object show all
Defined in:
lib/vips/operation.rb

Defined Under Namespace

Modules: OperationLayout Classes: ManagedStruct, Struct

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Object

#get, #get_pspec, #get_typeof, #get_typeof_error, print_all

Methods inherited from GObject::GObject

#ffi_managed_struct, ffi_managed_struct, #ffi_struct, ffi_struct

Constructor Details

#initialize(value) ⇒ Operation

Returns a new instance of Operation



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# File 'lib/vips/operation.rb', line 60

def initialize value
    # allow init with a pointer so we can wrap the return values from
    # things like _build
    if value.is_a? String
        value = Vips::vips_operation_new value
        raise Vips::Error if value == nil
    end

    super value
end

Class Method Details

.call(name, supplied, optional = {}, option_string = "") ⇒ Object

This is the public entry point for the vips binding. call will run any vips operation, for example:

out = Vips::Operation.call "black", [100, 100], {:bands => 12}

will call the C function

vips_black( &out, 100, 100, "bands", 12, NULL );

There are Image#method_missing hooks which will run call for you on Image for undefined instance or class methods. So you can also write:

out = Vips::Image.black 100, 100, bands: 12

Or perhaps:

x = Vips::Image.black 100, 100
y = x.invert

to run the vips_invert() operator.

There are also a set of operator overloads and some convenience functions, see Image.

If the operator needs a vector constant, call will turn a scalar into a vector for you. So for x.linear a, b, which calculates x * a + b where a and b are vector constants, you can write:

x = Vips::Image.black 100, 100, bands: 3
y = x.linear 1, 2
y = x.linear [1], 4
y = x.linear [1, 2, 3], 4

or any other combination. The operator overloads use this facility to support all the variations on:

x = Vips::Image.black 100, 100, bands: 3
y = x * 2
y = x + [1,2,3]
y = x % [1]

Similarly, wherever an image is required, you can use a constant. The constant will be expanded to an image matching the first input image argument. For example, you can write:

x = Vips::Image.black 100, 100, bands: 3
y = x.bandjoin 255

to add an extra band to the image where each pixel in the new band has the constant value 255.



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# File 'lib/vips/operation.rb', line 226

def self.call name, supplied, optional = {}, option_string = ""
    GLib::logger.debug("Vips::VipsOperation.call") {
        "name = #{name}, supplied = #{supplied}, " +
        "optional = #{optional}, option_string = #{option_string}"
    }

    op = Operation.new name

    # find and classify all the arguments the operator can take
    args = op.get_construct_args
    required_input = [] 
    optional_input = {}
    required_output = [] 
    optional_output = {}
    args.each do |name, flags|
        next if (flags & ARGUMENT_DEPRECATED) != 0

        if (flags & ARGUMENT_INPUT) != 0 
            if (flags & ARGUMENT_REQUIRED) != 0 
                required_input << [name, flags]
            else
                optional_input[name] = flags
            end
        end

        # MODIFY INPUT args count as OUTPUT as well
        if (flags & ARGUMENT_OUTPUT) != 0 ||
            ((flags & ARGUMENT_INPUT) != 0 &&
             (flags & ARGUMENT_MODIFY) != 0)
            if (flags & ARGUMENT_REQUIRED) != 0
                required_output << [name, flags]
            else
                optional_output[name] = flags
            end
        end

    end

    # so we should have been supplied with n_required_input values, or
    # n_required_input + 1 if there's a hash of options at the end
    unless supplied.is_a? Array
        raise Vips::Error, "unable to call #{name}: " + 
            "argument array is not an array"
    end
    unless optional.is_a? Hash
        raise Vips::Error, "unable to call #{name}: " + 
            "optional arguments are not a hash"
    end
    if supplied.length != required_input.length 
        raise Vips::Error, "unable to call #{name}: " + 
            "you supplied #{supplied.length} arguments, " +
            "but operation needs #{required_input.length}."
    end

    # very that all supplied_optional keys are in optional_input or
    # optional_output
    optional.each do |key, value|
        arg_name = key.to_s

        unless optional_input.has_key?(arg_name) ||
            optional_output.has_key?(arg_name)
            raise Vips::Error, "unable to call #{name}: " + 
                "unknown option #{arg_name}"
        end
    end

    # the first image arg is the thing we expand constants to match ...
    # we need to find it
    #
    # look inside array and hash arguments, since we may be passing an
    # array of images
    match_image = find_inside(supplied) do |value|
        value.is_a? Image
    end

    # set any string args first so they can't be overridden
    if option_string != nil
        if Vips::vips_object_set_from_string(op, option_string) != 0
            raise Vips::Error
        end
    end

    # set all required inputs
    required_input.each_index do |i|
        arg_name = required_input[i][0]
        flags = required_input[i][1]
        value = supplied[i]

        op.set arg_name, value, match_image, flags
    end

    # set all optional inputs
    optional.each do |key, value|
        next if value.nil?

        arg_name = key.to_s

        if optional_input.has_key? arg_name
            flags = optional_input[arg_name]

            op.set arg_name, value, match_image, flags
        end
    end

    op = op.build

    # get all required results
    result = []
    required_output.each do |arg_name, flags|
        result << op.get(arg_name)
    end

    # fetch all optional ones
    optional_results = {}
    optional.each do |key, value|
        arg_name = key.to_s

        if optional_output.has_key? arg_name
            flags = optional_output[arg_name]

            optional_results[arg_name] = op.get arg_name
        end
    end

    result << optional_results if optional_results != {}

    if result.length == 1
        result = result.first
    elsif result.length == 0
        result = nil
    end

    GLib::logger.debug("Vips::Operation.call") {"result = #{result}"}

    Vips::vips_object_unref_outputs op

    return result
end

.find_inside(object, &block) ⇒ Object

search array for the first element to match a predicate ... search inside subarrays and sub-hashes



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# File 'lib/vips/operation.rb', line 112

def self.find_inside object, &block
    return object if block.call object

    if object.is_a? Enumerable
        object.find {|value| block.call value, block}
    end

    return nil
end

.imageize(match_image, value) ⇒ Object

expand a constant into an image



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# File 'lib/vips/operation.rb', line 123

def self.imageize match_image, value
    return value if value.is_a? Image

    # 2D array values become tiny 2D images
    # if there's nothing to match to, we also make a 2D image
    if (value.is_a?(Array) && value[0].is_a?(Array)) || 
        match_image == nil
        return Image.new_from_array value
    else
        # we have a 1D array ... use that as a pixel constant and
        # expand to match match_image
        return match_image.new_from_image value
    end
end

Instance Method Details

#argument_map(&block) ⇒ Object



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# File 'lib/vips/operation.rb', line 80

def argument_map &block
    fn = Proc.new do |op, pspec, argument_class, argument_instance, a, b|
        block.call pspec, argument_class, argument_instance
    end

    Vips::vips_argument_map self, fn, nil, nil
end

#buildObject



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# File 'lib/vips/operation.rb', line 71

def build 
    op = Vips::vips_cache_operation_build self 
    if op == nil
        raise Vips::Error
    end

    return Operation.new op
end

#get_construct_argsObject

not quick! try to call this infrequently



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# File 'lib/vips/operation.rb', line 93

def get_construct_args
    args = []

    argument_map do |pspec, argument_class, argument_instance|
        flags = argument_class[:flags]
        if (flags & ARGUMENT_CONSTRUCT) != 0 
            # names can include - as punctuation, but we always use _ in
            # Ruby
            name = pspec[:name].tr("-", "_")

            args << [name, flags] 
        end
    end

    return args
end

#get_flagsObject



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# File 'lib/vips/operation.rb', line 88

def get_flags
    Vips::vips_operation_get_flags self
end

#set(name, value, match_image = nil, flags = 0) ⇒ Object

set an operation argument, expanding constants and copying images as required



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# File 'lib/vips/operation.rb', line 140

def set name, value, match_image = nil, flags = 0
    gtype = get_typeof name

    if gtype == IMAGE_TYPE 
        value = Operation::imageize match_image, value

        if (flags & ARGUMENT_MODIFY) != 0
            # make sure we have a unique copy
            value = value.copy.copy_memory
        end
    elsif gtype == ARRAY_IMAGE_TYPE
        value = value.map {|x| Operation::imageize match_image, x}
    end

    super name, value
end