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# This module provides an interface to the top level bits of libvips
# via ruby-ffi.
#
# Author:: John Cupitt (mailto:jcupitt@gmail.com)
# License:: MIT
require "ffi"
module Vips
attach_function :vips_region_new, [:pointer], :pointer
if Vips.at_least_libvips?(8, 8)
attach_function :vips_region_fetch, [:pointer, :int, :int, :int, :int, SizeStruct.ptr], :pointer
attach_function :vips_region_width, [:pointer], :int
attach_function :vips_region_height, [:pointer], :int
end
# A region on an image. Create one, then use `fetch` to quickly get a region
# of pixels.
#
# For example:
#
# ```ruby
# region = Vips::Region.new(image)
# pixels = region.fetch(10, 10, 100, 100)
# ```
class Region < Vips::Object
# The layout of the VipsRegion struct.
module RegionLayout
def self.included(base)
base.class_eval do
layout :parent, Vips::Object::Struct
# rest opaque
end
end
end
class Struct < Vips::Object::Struct
include RegionLayout
end
class ManagedStruct < Vips::Object::ManagedStruct
include RegionLayout
end
def initialize(name)
ptr = Vips.vips_region_new name
raise Vips::Error if ptr.null?
super ptr
end
def width
Vips.vips_region_width self
end
def height
Vips.vips_region_height self
end
# Fetch a region filled with pixel data.
def fetch(left, top, width, height)
len = Vips::SizeStruct.new
ptr = Vips.vips_region_fetch self, left, top, width, height, len
raise Vips::Error if ptr.null?
# wrap up as an autopointer
ptr = FFI::AutoPointer.new(ptr, GLib::G_FREE)
ptr.get_bytes 0, len[:value]
end
end
end
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