Class: GDAL::GeoTransform

Inherits:
Object
  • Object
show all
Includes:
Extensions
Defined in:
lib/gdal/geo_transform.rb,
lib/gdal/extensions/geo_transform/extensions.rb

Defined Under Namespace

Modules: Extensions

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Extensions

included, #to_a, #world_to_pixel, #world_to_x_pixel, #world_to_y_pixel

Constructor Details

#initialize(geo_transform = nil) ⇒ GeoTransform

Returns a new instance of GeoTransform.

Parameters:

  • geo_transform (FFI::Pointer) (defaults to: nil) 


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# File 'lib/gdal/geo_transform.rb', line 34

def initialize(geo_transform = nil)
  @c_pointer = geo_transform ? GDAL._pointer(GDAL::GeoTransform, geo_transform) : self.class.new_pointer

  self.pixel_width ||= 1.0
  self.pixel_height ||= 1.0
  self.x_rotation ||= 0.0
  self.y_rotation ||= 0.0
end

Instance Attribute Details

#c_pointer ⇒ FFI::Pointer (readonly)

Returns C pointer to the C geo-transform.

Returns:

  • (FFI::Pointer) —

    C pointer to the C geo-transform.



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# File 'lib/gdal/geo_transform.rb', line 13

def c_pointer
  @c_pointer
end

Class Method Details

.from_world_file(filename, extension = nil) ⇒ GDAL::GeoTransform

Parameters:

  • filename (String)
  • extension (String) (defaults to: nil) —

    The file extension to use. When nil, GDAL will try to derive it from the filename.

Returns:



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# File 'lib/gdal/geo_transform.rb', line 19

def self.from_world_file(filename, extension = nil)
  gt_ptr = new_pointer

  result = if extension
             FFI::GDAL::GDAL.GDALReadWorldFile(filename, extension, gt_ptr)
           else
             FFI::GDAL::GDAL.GDALLoadWorldFile(filename, gt_ptr)
           end

  return nil unless result

  new(gt_ptr)
end

.new_pointer ⇒ FFI::MemoryPointer

Returns A pointer that can be used to hold a GeoTransform.

Returns:

  • (FFI::MemoryPointer) —

    A pointer that can be used to hold a GeoTransform.



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# File 'lib/gdal/geo_transform.rb', line 8

def self.new_pointer
  FFI::MemoryPointer.new(:double, 6)
end

Instance Method Details

#apply_geo_transform(pixel, line) ⇒ Hash{x_geo => Float, y_geo => Float} Also known as: pixel_to_world

Converts a (pixel, line) coordinate to a georeferenced (geo_x, geo_y) location. Uses the following algorithm:

geo_x = x_origin + (pixel * pixel_width) + (line * pixel_rotation)
geo_y = y_origin + (pixel * y_rotation) + (line * pixel_height)

This is also the same as doing:

geo_transform.invert.world_to_pixel(pixel, line)

# easting/longitude; :y_geo is the northing/latitude.

Parameters:

  • pixel (Float) —

    Input pixel position.

  • line (Float) —

    Input line position.

Returns:

  • (Hash{x_geo => Float, y_geo => Float}) —

    :x_geo is the



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# File 'lib/gdal/geo_transform.rb', line 151

def apply_geo_transform(pixel, line)
  geo_x_ptr = FFI::MemoryPointer.new(:double)
  geo_y_ptr = FFI::MemoryPointer.new(:double)
  FFI::GDAL::GDAL.GDALApplyGeoTransform(@c_pointer, pixel, line, geo_x_ptr, geo_y_ptr)

  { x_geo: geo_x_ptr.read_double, y_geo: geo_y_ptr.read_double }
end

#compose(other_geo_transform) ⇒ GDAL::GeoTransform

Composes this and the given geo_transform. The resulting GeoTransform is equivalent to applying both GeoTransforms to a point.

Parameters:

Returns:

Raises:



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# File 'lib/gdal/geo_transform.rb', line 165

def compose(other_geo_transform)
  other_ptr = GDAL._pointer(GDAL::GeoTransform, other_geo_transform)

  raise GDAL::NullObject, "Unable to access pointer for '#{other_geo_transform}'" unless other_ptr

  new_gt_ptr = self.class.new_pointer
  FFI::GDAL::GDAL.GDALComposeGeoTransforms(@c_pointer, other_ptr, new_gt_ptr)
  return nil if new_gt_ptr.null?

  GDAL::GeoTransform.new(new_gt_ptr)
end

#invert ⇒ GDAL::GeoTransform

Inverts the current 3x2 set of coefficients and returns a new GeoTransform. Useful for converting from the GeoTransform equation from pixel to geo to being geo to pixel.

Returns:



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# File 'lib/gdal/geo_transform.rb', line 182

def invert
  new_geo_transform_ptr = self.class.new_pointer
  success = FFI::GDAL::GDAL.GDALInvGeoTransform(@c_pointer, new_geo_transform_ptr)
  return nil unless success

  self.class.new(new_geo_transform_ptr)
end

#null? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/gdal/geo_transform.rb', line 43

def null?
  @c_pointer.null?
end

#pixel_height ⇒ Float

AKA Y-pixel size. In wikipedia’s World Map definition, this is “E”.

Returns:



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# File 'lib/gdal/geo_transform.rb', line 126

def pixel_height
  return nil if null?

  @c_pointer[5].read_double
end

#pixel_height=(new_pixel_height) ⇒ Object

Parameters:

  • new_pixel_height (Float) 


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# File 'lib/gdal/geo_transform.rb', line 133

def pixel_height=(new_pixel_height)
  @c_pointer[5].write_double(new_pixel_height)
end

#pixel_width ⇒ Float

AKA X-pixel size. In wikipedia’s World Map definition, this is “A”.

Returns:



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# File 'lib/gdal/geo_transform.rb', line 66

def pixel_width
  return nil if null?

  @c_pointer[1].read_double
end

#pixel_width=(new_pixel_width) ⇒ Object

Parameters:

  • new_pixel_width (Float) 


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# File 'lib/gdal/geo_transform.rb', line 73

def pixel_width=(new_pixel_width)
  @c_pointer[1].write_double(new_pixel_width)
end

#to_world_file(raster_filename, world_extension) ⇒ Boolean

Parameters:

  • raster_filename (String) —

    The target raster file.

  • world_extension (String)

Returns:

  • (Boolean) 


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# File 'lib/gdal/geo_transform.rb', line 193

def to_world_file(raster_filename, world_extension)
  FFI::GDAL::GDAL.GDALWriteWorldFile(raster_filename, world_extension, @c_pointer)
end

#x_origin ⇒ Float

X-coordinate of the center of the upper left pixel. In wikipedia’s World Map definition, this is “C”.

Returns:



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# File 'lib/gdal/geo_transform.rb', line 51

def x_origin
  return nil if null?

  @c_pointer[0].read_double
end

#x_origin=(new_x_origin) ⇒ Object

Parameters:



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# File 'lib/gdal/geo_transform.rb', line 58

def x_origin=(new_x_origin)
  @c_pointer[0].write_double(new_x_origin)
end

#x_rotation ⇒ Float

Rotation about the x-axis. In wikipedia’s World File definition, this is “B”.

Returns:



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# File 'lib/gdal/geo_transform.rb', line 81

def x_rotation
  return nil if null?

  @c_pointer[2].read_double
end

#x_rotation=(new_x_rotation) ⇒ Object

Parameters:



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# File 'lib/gdal/geo_transform.rb', line 88

def x_rotation=(new_x_rotation)
  @c_pointer[2].write_double(new_x_rotation)
end

#y_origin ⇒ Float

Y-coordinate of the center of the upper left pixel. In wikipedia’s World Map definition, this is “F”.

Returns:



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# File 'lib/gdal/geo_transform.rb', line 96

def y_origin
  return nil if null?

  @c_pointer[3].read_double
end

#y_origin=(new_y_origin) ⇒ Object

Parameters:



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# File 'lib/gdal/geo_transform.rb', line 103

def y_origin=(new_y_origin)
  @c_pointer[3].write_double(new_y_origin)
end

#y_rotation ⇒ Float

Rotation about the y-axis. In wikipedia’s World Map definition, this is “D”.

Returns:



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# File 'lib/gdal/geo_transform.rb', line 111

def y_rotation
  return nil if null?

  @c_pointer[4].read_double
end

#y_rotation=(new_y_rotation) ⇒ Object

Parameters:



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# File 'lib/gdal/geo_transform.rb', line 118

def y_rotation=(new_y_rotation)
  @c_pointer[4].write_double(new_y_rotation)
end