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image.rb
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image.rb
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# This module provides an interface to the vips image processing library
# via ruby-ffi.
#
# Author:: John Cupitt (mailto:jcupitt@gmail.com)
# License:: MIT
require "ffi"
module Vips
private
attach_function :vips_image_new_matrix_from_array,
[:int, :int, :pointer, :int], :pointer
attach_function :vips_image_copy_memory, [:pointer], :pointer
attach_function :vips_image_set_progress, [:pointer, :bool], :void
attach_function :vips_image_set_kill, [:pointer, :bool], :void
attach_function :vips_filename_get_filename, [:string], :pointer
attach_function :vips_filename_get_options, [:string], :pointer
attach_function :vips_foreign_find_load, [:string], :string
attach_function :vips_foreign_find_save, [:string], :string
attach_function :vips_foreign_find_load_buffer, [:pointer, :size_t], :string
attach_function :vips_foreign_find_save_buffer, [:string], :string
if Vips.at_least_libvips?(8, 9)
attach_function :vips_foreign_find_load_source, [:pointer], :string
attach_function :vips_foreign_find_save_target, [:string], :string
end
attach_function :vips_image_write_to_memory,
[:pointer, SizeStruct.ptr], :pointer
attach_function :vips_image_get_typeof, [:pointer, :string], :GType
attach_function :vips_image_get,
[:pointer, :string, GObject::GValue.ptr], :int
attach_function :vips_image_get_width, [:pointer], :int
attach_function :vips_image_get_height, [:pointer], :int
attach_function :vips_image_get_bands, [:pointer], :int
if Vips.at_least_libvips?(8, 5)
attach_function :vips_image_get_fields, [:pointer], :pointer
attach_function :vips_image_hasalpha, [:pointer], :int
end
if Vips.at_least_libvips?(8, 6)
attach_function :vips_addalpha, [:pointer, :pointer, :varargs], :int
end
# move these three lines to mutableimage when we finally remove set and
# remove in this class
attach_function :vips_image_set,
[:pointer, :string, GObject::GValue.ptr], :void
attach_function :vips_image_remove, [:pointer, :string], :void
attach_function :vips_band_format_iscomplex, [:int], :int
attach_function :vips_band_format_isfloat, [:int], :int
attach_function :nickname_find, :vips_nickname_find, [:GType], :string
attach_function :vips_image_new_from_memory, [:pointer, :size_t, :int, :int, :int, :int], :pointer
attach_function :vips_image_new_from_memory_copy, [:pointer, :size_t, :int, :int, :int, :int], :pointer
# turn a raw pointer that must be freed into a self-freeing Ruby string
def self.p2str(pointer)
pointer = FFI::AutoPointer.new(pointer, GLib::G_FREE)
pointer.read_string
end
public
# This class represents a libvips image. See the {Vips} module documentation
# for an introduction to using this class.
class Image < Vips::Object
alias_method :parent_get_typeof, :get_typeof
# FFI sets a pointer's size to this magic value if the size of the memory
# chunk the pointer points to is unknown to FFI.
UNKNOWN_POINTER_SIZE = FFI::Pointer.new(1).size
private_constant :UNKNOWN_POINTER_SIZE
private
# the layout of the VipsImage struct
module ImageLayout
def self.included base
base.class_eval do
layout :parent, Vips::Object::Struct
# rest opaque
end
end
end
class Struct < Vips::Object::Struct
include ImageLayout
end
class ManagedStruct < Vips::Object::ManagedStruct
include ImageLayout
end
class GenericPtr < FFI::Struct
layout :value, :pointer
end
# handy for overloads ... want to be able to apply a function to an
# array or to a scalar
def self.smap x, &block
x.is_a?(Array) ? x.map { |y| smap(y, &block) } : block.call(x)
end
def self.complex? format
format_number = GObject::GValue.from_nick BAND_FORMAT_TYPE, format
Vips.vips_band_format_iscomplex(format_number) != 0
end
def self.float? format
format_number = GObject::GValue.from_nick BAND_FORMAT_TYPE, format
Vips.vips_band_format_isfloat(format_number) != 0
end
# run a complex operation on a complex image, or an image with an even
# number of bands ... handy for things like running .polar on .index
# images
def self.run_cmplx image, &block
original_format = image.format
unless Image.complex? image.format
if image.bands % 2 != 0
raise Vips::Error, "not an even number of bands"
end
unless Image.float? image.format
image = image.cast :float
end
new_format = (image.format == :double) ? :dpcomplex : :complex
image = image.copy format: new_format, bands: image.bands / 2
end
image = block.call(image)
unless Image.complex? original_format
new_format = (image.format == :dpcomplex) ? :double : :float
image = image.copy format: new_format, bands: image.bands * 2
end
image
end
# handy for expanding enum operations
def call_enum(name, other, enum)
if other.is_a?(Vips::Image)
Vips::Operation.call name.to_s, [self, other, enum]
else
Vips::Operation.call name.to_s + "_const", [self, enum, other]
end
end
# Write can fail due to no file descriptors and memory can fill if
# large objects are not collected fairly soon. We can't try a
# write and GC and retry on fail, since the write may take a
# long time and may not be repeatable.
#
# GCing before every write would have a horrible effect on
# performance, so as a compromise we GC every @@gc_interval writes.
#
# ruby2.1 introduced a generational GC which is fast enough to be
# able to GC on every write.
@@generational_gc = RUBY_ENGINE == "ruby" && RUBY_VERSION.to_f >= 2.1
@@gc_interval = 100
@@gc_countdown = @@gc_interval
def write_gc
if @@generational_gc
GC.start full_mark: false
else
@@gc_countdown -= 1
if @@gc_countdown < 0
@@gc_countdown = @@gc_interval
GC.start
end
end
end
public
def inspect
"#<Image #{width}x#{height} #{format}, #{bands} bands, #{interpretation}>"
end
def respond_to? name, include_all = false
# To support keyword args, we need to tell Ruby that final image
# arguments cannot be hashes of keywords.
#
# https://makandracards.com/makandra/
# 36013-heads-up-ruby-implicitly-converts-a-hash-to-keyword-arguments
return false if name == :to_hash
super
end
def respond_to_missing? name, include_all = false
# respond to all vips operations by nickname
return true if Vips.type_find("VipsOperation", name.to_s) != 0
super
end
def self.respond_to_missing? name, include_all = false
# respond to all vips operations by nickname
return true if Vips.type_find("VipsOperation", name.to_s) != 0
super
end
# Invoke a vips operation with {Vips::Operation.call}, using self as
# the first input argument.
#
# @param name [String] vips operation to call
# @return result of vips operation
def method_missing name, *args, **options
Vips::Operation.call name.to_s, [self, *args], options
end
# Invoke a vips operation with {Vips::Operation.call}.
def self.method_missing name, *args, **options
Vips::Operation.call name.to_s, args, options
end
# Return a new {Image} for a file on disc. This method can load
# images in any format supported by vips. The filename can include
# load options, for example:
#
# ```
# image = Vips::Image.new_from_file "fred.jpg[shrink=2]"
# ```
#
# You can also supply options as a hash, for example:
#
# ```
# image = Vips::Image.new_from_file "fred.jpg", shrink: 2
# ```
#
# The full set of options available depend upon the load operation that
# will be executed. Try something like:
#
# ```
# $ vips jpegload
# ```
#
# at the command-line to see a summary of the available options for the
# JPEG loader.
#
# Loading is fast: only enough of the image is loaded to be able to fill
# out the header. Pixels will only be decompressed when they are needed.
#
# @!macro [new] vips.loadopts
# @param opts [Hash] set of options
# @option opts [Boolean] :disc (true) Open large images via a
# temporary disc file
# @option opts [Vips::Access] :access (:random) Access mode for file
#
# @param name [String] the filename to load from
# @macro vips.loadopts
# @return [Image] the loaded image
def self.new_from_file name, **opts
# very common, and Vips::vips_filename_get_filename will segv if we
# pass this
raise Vips::Error, "filename is nil" if name.nil?
filename = Vips.p2str(Vips.vips_filename_get_filename(name))
option_string = Vips.p2str(Vips.vips_filename_get_options(name))
loader = Vips.vips_foreign_find_load filename
raise Vips::Error if loader.nil?
Operation.call loader, [filename], opts, option_string
end
# Create a new {Image} for an image encoded in a format such as
# JPEG in a binary string. Load options may be passed as
# strings or appended as a hash. For example:
#
# ```
# image = Vips::Image.new_from_buffer memory_buffer, "shrink=2"
# ```
#
# or alternatively:
#
# ```
# image = Vips::Image.new_from_buffer memory_buffer, "", shrink: 2
# ```
#
# The options available depend on the file format. Try something like:
#
# ```
# $ vips jpegload_buffer
# ```
#
# at the command-line to see the available options. Not all loaders
# support load from buffer, but at least JPEG, PNG and
# TIFF images will work.
#
# Loading is fast: only enough of the image is loaded to be able to fill
# out the header. Pixels will only be decompressed when they are needed.
#
# @param data [String] the data to load from
# @param option_string [String] load options as a string
# @macro vips.loadopts
# @return [Image] the loaded image
def self.new_from_buffer data, option_string, **opts
loader = Vips.vips_foreign_find_load_buffer data, data.bytesize
raise Vips::Error if loader.nil?
Vips::Operation.call loader, [data], opts, option_string
end
# Create a new {Image} from a C-style array held in memory. For example:
#
# ```
# image = Vips::Image.black(16, 16) + 128
# data = image.write_to_memory
#
# x = Vips::Image.new_from_memory data,
# image.width, image.height, image.bands, image.format
# ```
#
# Creating a new image from a memory pointer:
#
# ```
# ptr = FFI::MemoryPointer.new(:uchar, 10*10)
# # => #<FFI::MemoryPointer address=0x00007fc236db31d0 size=100>
# x = Vips::Image.new_from_memory(ptr, 10, 10, 1, :uchar)
# ```
#
# Creating a new image from an address only pointer:
#
# ```
# ptr = call_to_external_c_library(w: 10, h: 10)
# # => #<FFI::Pointer address=0x00007f9780813a00>
# ptr_slice = ptr.slice(0, 10*10)
# # => #<FFI::Pointer address=0x00007f9780813a00 size=100>
# x = Vips::Image.new_from_memory(ptr_slice, 10, 10, 1, :uchar)
# ```
#
# {new_from_memory} keeps a reference to the array of pixels you pass in
# to try to prevent that memory from being freed by the Ruby GC while it
# is being used.
#
# See {new_from_memory_copy} for a version of this method which does not
# keep a reference.
#
# @param data [String, FFI::Pointer] the data to load from
# @param width [Integer] width in pixels
# @param height [Integer] height in pixels
# @param bands [Integer] number of bands
# @param format [Symbol] band format
# @return [Image] the loaded image
def self.new_from_memory data, width, height, bands, format
# prevent data from being freed with JRuby FFI
if defined?(JRUBY_VERSION) && !data.is_a?(FFI::Pointer)
data = ::FFI::MemoryPointer.new(:char, data.bytesize).write_bytes data
end
if data.is_a?(FFI::Pointer)
# A pointer needs to know about the size of the memory it points to.
# If you have an address-only pointer, use the .slice method to wrap
# the pointer in a size aware pointer.
if data.size == UNKNOWN_POINTER_SIZE
raise Vips::Error, "size of memory is unknown"
end
size = data.size
else
size = data.bytesize
end
format_number = GObject::GValue.from_nick BAND_FORMAT_TYPE, format
vi = Vips.vips_image_new_from_memory data, size,
width, height, bands, format_number
raise Vips::Error if vi.null?
image = new(vi)
# keep a secret ref to the underlying object .. this reference will be
# inherited by things that in turn depend on us, so the memory we are
# using will not be freed
image.references << data
image
end
# Create a new {Image} from memory and copies the memory area. See
# {new_from_memory} for a version of this method which does not copy the
# memory area.
#
# @param data [String, FFI::Pointer] the data to load from
# @param width [Integer] width in pixels
# @param height [Integer] height in pixels
# @param bands [Integer] number of bands
# @param format [Symbol] band format
# @return [Image] the loaded image
def self.new_from_memory_copy data, width, height, bands, format
format_number = GObject::GValue.from_nick BAND_FORMAT_TYPE, format
if data.is_a?(FFI::Pointer)
if data.size == UNKNOWN_POINTER_SIZE
raise Vips::Error, "size of memory is unknown"
end
size = data.size
else
size = data.bytesize
end
vi = Vips.vips_image_new_from_memory_copy data, size,
width, height, bands, format_number
raise Vips::Error if vi.null?
new(vi)
end
# Create a new {Image} from a source. Load options may be passed as
# strings or appended as a hash. For example:
#
# ```
# source = Vips::Source.new_from_file("k2.jpg")
# image = Vips::Image.new_from_source source, "shrink=2"
# ```
#
# or alternatively:
#
# ```
# image = Vips::Image.new_from_source source, "", shrink: 2
# ```
#
# The options available depend on the file format. Try something like:
#
# ```
# $ vips jpegload_source
# ```
#
# at the command-line to see the available options. Not all loaders
# support load from source, but at least JPEG, PNG and
# TIFF images will work.
#
# Loading is fast: only enough data is read to be able to fill
# out the header. Pixels will only be read and decompressed when they are
# needed.
#
# @param source [Vips::Source] the source to load from
# @param option_string [String] load options as a string
# @macro vips.loadopts
# @return [Image] the loaded image
def self.new_from_source source, option_string, **opts
loader = Vips.vips_foreign_find_load_source source
raise Vips::Error if loader.nil?
result = Vips::Operation.call loader, [source], opts, option_string
# keep a secret ref to the source object ... the libvips loader will
# keep a ref to the C source object, but we need the ruby wrapper object
# to stay alive too
result.references << source
result
end
def self.matrix_from_array width, height, array
ptr = FFI::MemoryPointer.new :double, array.length
ptr.write_array_of_double array
image = Vips.vips_image_new_matrix_from_array width, height,
ptr, array.length
Vips::Image.new image
end
# Create a new Image from a 1D or 2D array. A 1D array becomes an
# image with height 1. Use `scale` and `offset` to set the scale and
# offset fields in the header. These are useful for integer
# convolutions.
#
# For example:
#
# ```
# image = Vips::Image.new_from_array [1, 2, 3]
# ```
#
# or
#
# ```
# image = Vips::Image.new_from_array [
# [-1, -1, -1],
# [-1, 16, -1],
# [-1, -1, -1]], 8
# ```
#
# for a simple sharpening mask.
#
# @param array [Array] the pixel data as an array of numbers
# @param scale [Real] the convolution scale
# @param offset [Real] the convolution offset
# @return [Image] the image
def self.new_from_array array, scale = 1, offset = 0
# we accept a 1D array and assume height == 1, or a 2D array
# and check all lines are the same length
unless array.is_a? Array
raise Vips::Error, "Argument is not an array."
end
if array[0].is_a? Array
height = array.length
width = array[0].length
unless array.all? { |x| x.is_a? Array }
raise Vips::Error, "Not a 2D array."
end
unless array.all? { |x| x.length == width }
raise Vips::Error, "Array not rectangular."
end
array = array.flatten
else
height = 1
width = array.length
end
unless array.length == width * height
raise Vips::Error, "Bad array dimensions."
end
unless array.all? { |x| x.is_a? Numeric }
raise Vips::Error, "Not all array elements are Numeric."
end
image = Vips::Image.matrix_from_array width, height, array
raise Vips::Error if image.nil?
image.mutate do |mutable|
# be careful to set them as double
mutable.set_type! GObject::GDOUBLE_TYPE, "scale", scale.to_f
mutable.set_type! GObject::GDOUBLE_TYPE, "offset", offset.to_f
end
end
# A new image is created with the same width, height, format,
# interpretation, resolution and offset as self, but with every pixel
# set to the specified value.
#
# You can pass an array to make a many-band image, or a single value to
# make a one-band image.
#
# @param value [Real, Array<Real>] value to put in each pixel
# @return [Image] constant image
def new_from_image value
pixel = (Vips::Image.black(1, 1) + value).cast(format)
image = pixel.embed 0, 0, width, height, extend: :copy
image.copy interpretation: interpretation, xres: xres, yres: yres,
xoffset: xoffset, yoffset: yoffset
end
# Write this image to a file. Save options may be encoded in the
# filename or given as a hash. For example:
#
# ```
# image.write_to_file "fred.jpg[Q=90]"
# ```
#
# or equivalently:
#
# ```
# image.write_to_file "fred.jpg", Q: 90
# ```
#
# The full set of save options depend on the selected saver. Try
# something like:
#
# ```
# $ vips jpegsave
# ```
#
# to see all the available options for JPEG save.
#
# @!macro [new] vips.saveopts
# @param opts [Hash] set of options
# @option opts [Boolean] :strip (false) Strip all metadata from image
# @option opts [Array<Float>] :background (0) Background colour to
# flatten alpha against, if necessary
#
# @param name [String] filename to write to
def write_to_file name, **opts
raise Vips::Error, "filename is nil" if name.nil?
filename = Vips.p2str(Vips.vips_filename_get_filename(name))
option_string = Vips.p2str(Vips.vips_filename_get_options(name))
saver = Vips.vips_foreign_find_save filename
raise Vips::Error if saver.nil?
Vips::Operation.call saver, [self, filename], opts, option_string
write_gc
end
# Write this image to a memory buffer. Save options may be encoded in
# the format_string or given as a hash. For example:
#
# ```
# buffer = image.write_to_buffer ".jpg[Q=90]"
# ```
#
# or equivalently:
#
# ```
# image.write_to_buffer ".jpg", Q: 90
# ```
#
# The full set of save options depend on the selected saver. Try
# something like:
#
# ```
# $ vips jpegsave
# ```
#
# to see all the available options for JPEG save.
#
# @param format_string [String] save format plus options
# @macro vips.saveopts
# @return [String] the image saved in the specified format
def write_to_buffer format_string, **opts
raise Vips::Error, "filename is nil" if format_string.nil?
filename = Vips.p2str(Vips.vips_filename_get_filename(format_string))
option_string = Vips.p2str(Vips.vips_filename_get_options(format_string))
# try to save with the new target API first, only fall back to the old
# buffer API if there's no target save for this filetype
saver = nil
if Vips.at_least_libvips?(8, 9)
Vips.vips_error_freeze
saver = Vips.vips_foreign_find_save_target filename
Vips.vips_error_thaw
end
if !saver.nil?
target = Vips::Target.new_to_memory
Vips::Operation.call saver, [self, target], opts, option_string
buffer = target.get("blob")
else
saver = Vips.vips_foreign_find_save_buffer filename
raise Vips::Error if saver.nil?
buffer = Vips::Operation.call saver, [self], opts, option_string
raise Vips::Error if buffer.nil?
end
write_gc
buffer
end
# Write this image to a target. Save options may be encoded in
# the format_string or given as a hash. For example:
#
# ```ruby
# target = Vips::Target.new_to_file "k2.jpg"
# image.write_to_target target, ".jpg[Q=90]"
# ```
#
# or equivalently:
#
# ```ruby
# image.write_to_target target, ".jpg", Q: 90
# ```
#
# The full set of save options depend on the selected saver. Try
# something like:
#
# ```
# $ vips jpegsave_target
# ```
#
# to see all the available options for JPEG save.
#
# @param target [Vips::Target] the target to write to
# @param format_string [String] save format plus string options
# @macro vips.saveopts
def write_to_target target, format_string, **opts
raise Vips::Error, "filename is nil" if format_string.nil?
filename = Vips.p2str(Vips.vips_filename_get_filename(format_string))
option_string = Vips.p2str(Vips.vips_filename_get_options(format_string))
saver = Vips.vips_foreign_find_save_target filename
raise Vips::Error if saver.nil?
Vips::Operation.call saver, [self, target], opts, option_string
write_gc
end
# Write this image to a large memory buffer.
#
# @return [String] the pixels as a huge binary string
def write_to_memory
len = Vips::SizeStruct.new
ptr = Vips.vips_image_write_to_memory self, len
raise Vips::Error if ptr.nil?
# wrap up as an autopointer
ptr = FFI::AutoPointer.new(ptr, GLib::G_FREE)
ptr.get_bytes 0, len[:value]
end
# Turn progress signalling on and off.
#
# If this is on, the most-downstream image from this image will issue
# progress signals.
#
# @see Object#signal_connect
# @param state [Boolean] progress signalling state
def set_progress state
Vips.vips_image_set_progress self, state
end
# Kill computation of this time.
#
# Set true to stop computation of this image. You can call this from a
# progress handler, for example.
#
# @see Object#signal_connect
# @param kill [Boolean] stop computation
def set_kill kill
Vips.vips_image_set_kill self, kill
end
# Get the `GType` of a metadata field. The result is 0 if no such field
# exists.
#
# @see get
# @param name [String] Metadata field to fetch
# @return [Integer] GType
def get_typeof name
# on libvips before 8.5, property types must be searched first,
# since vips_image_get_typeof returned built-in enums as int
unless Vips.at_least_libvips?(8, 5)
gtype = parent_get_typeof name
return gtype if gtype != 0
end
Vips.vips_image_get_typeof self, name
end
# Get a metadata item from an image. Ruby types are constructed
# automatically from the `GValue`, if possible.
#
# For example, you can read the ICC profile from an image like this:
#
# ```
# profile = image.get "icc-profile-data"
# ```
#
# and profile will be an array containing the profile.
#
# @param name [String] Metadata field to get
# @return [Object] Value of field
def get name
# with old libvips, we must fetch properties (as opposed to
# metadata) via VipsObject
unless Vips.at_least_libvips?(8, 5)
return super if parent_get_typeof(name) != 0
end
gvalue = GObject::GValue.alloc
raise Vips::Error if Vips.vips_image_get(self, name, gvalue) != 0
result = gvalue.get
gvalue.unset
result
end
# Get the names of all fields on an image. Use this to loop over all
# image metadata.
#
# @return [[String]] array of field names
def get_fields
# vips_image_get_fields() was added in libvips 8.5
return [] unless Vips.respond_to? :vips_image_get_fields
array = Vips.vips_image_get_fields self
names = []
p = array
until (q = p.read_pointer).null?
names << q.read_string
GLib.g_free q
p += FFI::Type::POINTER.size
end
GLib.g_free array
names
end
# Mutate an image with a block. Inside the block, you can call methods
# which modify the image, such as setting or removing metadata, or
# modifying pixels.
#
# For example:
#
# ```ruby
# image = image.mutate do |x|
# (0 ... 1).step(0.01) do |i|
# x.draw_line! 255, x.width * i, 0, 0, x.height * (1 - i)
# end
# end
# ```
#
# See {MutableImage}.
def mutate
mutable = Vips::MutableImage.new self
yield mutable
mutable.image
end
# This method is deprecated.
#
# Please use {MutableImage#set_type!} instead.
def set_type gtype, name, value
gvalue = GObject::GValue.alloc
gvalue.init gtype
gvalue.set value
Vips.vips_image_set self, name, gvalue
gvalue.unset
end
# This method is deprecated.
#
# Please use {MutableImage#set!} instead.
def set name, value
set_type get_typeof(name), name, value
end
# This method is deprecated.
#
# Please use {MutableImage#remove!} instead.
def remove name
Vips.vips_image_remove self, name
end
# compatibility: old name for get
def get_value name
get name
end
# This method is deprecated.
#
# Please use {MutableImage#set!} instead.
def set_value name, value
set name, value
end
# Get image width, in pixels.
#
# @return [Integer] image width, in pixels
def width
Vips.vips_image_get_width self
end
# Get image height, in pixels.
#
# @return [Integer] image height, in pixels
def height
Vips.vips_image_get_height self
end
# Get number of image bands.
#
# @return [Integer] number of image bands
def bands
Vips.vips_image_get_bands self
end
# Get image format.
#
# @return [Symbol] image format
def format
get "format"
end
# Get image interpretation.
#
# @return [Symbol] image interpretation
def interpretation
get "interpretation"
end
# Get image coding.
#
# @return [Symbol] image coding
def coding
get "coding"
end
# Get image filename, if any.
#
# @return [String] image filename
def filename
get "filename"
end
# Get image xoffset.
#
# @return [Integer] image xoffset
def xoffset
get "xoffset"
end
# Get image yoffset.
#
# @return [Integer] image yoffset
def yoffset
get "yoffset"
end
# Get image x resolution.
#
# @return [Float] image x resolution
def xres
get "xres"
end
# Get image y resolution.
#
# @return [Float] image y resolution
def yres
get "yres"
end
# Get scale metadata.
#
# @return [Float] image scale
def scale
return 1 if get_typeof("scale") == 0
get "scale"
end
# Get offset metadata.
#
# @return [Float] image offset
def offset
return 0 if get_typeof("offset") == 0
get "offset"
end
# Get the image size.
#
# @return [Integer, Integer] image width and height
def size
[width, height]
end
if Vips.at_least_libvips?(8, 5)
# Detect if image has an alpha channel
#
# @return [Boolean] true if image has an alpha channel.
def has_alpha?
Vips.vips_image_hasalpha(self) != 0
end
end
# vips_addalpha was added in libvips 8.6
if Vips.at_least_libvips?(8, 6)
# Append an alpha channel to an image.
#
# @return [Image] new image
def add_alpha
ptr = GenericPtr.new
result = Vips.vips_addalpha self, ptr
raise Vips::Error if result != 0
Vips::Image.new ptr[:value]
end
end
# Copy an image to a memory area.
#
# This can be useful for reusing results, but can obviously use a lot of
# memory for large images. See {Image#tilecache} for a way of caching
# parts of an image.
#
# @return [Image] new memory image
def copy_memory
new_image = Vips.vips_image_copy_memory self
Vips::Image.new new_image
end
# Draw a point on an image.
#
# See {Image#draw_rect}.
#
# @return [Image] modified image
def draw_point ink, left, top, **opts