module ChunkyPNG::Canvas::Operations

The ChunkyPNG::Canvas::Operations module defines methods to perform operations on a {ChunkyPNG::Canvas}. The module is included into the Canvas class so all these methods are available on every canvas.

Note that some of these operations modify the canvas, while some operations return a new canvas and leave the original intact.

@see ChunkyPNG::Canvas

Public Instance Methods

border(size, color = ChunkyPNG::Color::BLACK) click to toggle source

Draws a border around the image.

@param [Integer] size The size of the border. @param [Integer] color The color of the border. @return [ChunkyPNG::Canvas] Returns a bordered version of the image. @see border!

# File lib/chunky_png/canvas/operations.rb, line 362
def border(size, color = ChunkyPNG::Color::BLACK)
  dup.border!(size, color)
end
border!(size, color = ChunkyPNG::Color::BLACK) click to toggle source

Draws a border around the image in place.

@param [Integer] size The size of the border. @param [Integer] color The color of the border. @return [ChunkyPNG::Canvas] Returns itself with the border added. @see border

# File lib/chunky_png/canvas/operations.rb, line 372
def border!(size, color = ChunkyPNG::Color::BLACK)
  new_width  = width  + size * 2
  new_height = height + size * 2

  bg = Canvas.new(new_width, new_height, color).replace(self, size, size)
  replace_canvas!(new_width, new_height, bg.pixels)
end
compose(other, offset_x = 0, offset_y = 0) click to toggle source

Composes another image onto this image using alpha blending. This will return a new canvas and leave the original intact.

If you simply want to replace pixels or when the other image does not have transparency, it is faster to use {replace}.

@param (see compose!) @return [ChunkyPNG::Canvas] Returns the new canvas, composed of the

other 2.

@raise [ChunkyPNG::OutOfBounds] when the other canvas doesn’t fit on

this one, given the offset and size of the other canvas.

@note API changed since 1.0 - This method now no longer is in place,

but returns a new canvas and leaves the original intact. Use
{#compose!} if you want to compose on the canvas in place.

@see replace

# File lib/chunky_png/canvas/operations.rb, line 85
def compose(other, offset_x = 0, offset_y = 0)
  dup.compose!(other, offset_x, offset_y)
end
compose!(other, offset_x = 0, offset_y = 0) click to toggle source

Composes another image onto this image using alpha blending. This will modify the current canvas.

If you simply want to replace pixels or when the other image does not have transparency, it is faster to use {replace!}.

@param [ChunkyPNG::Canvas] other The foreground canvas to compose on

the current canvas, using alpha compositing.

@param [Integer] offset_x The x-offset to apply the new foreground on. @param [Integer] offset_y The y-offset to apply the new foreground on. @return [ChunkyPNG::Canvas] Returns itself, but with the other canvas

composed onto it.

@raise [ChunkyPNG::OutOfBounds] when the other canvas doesn’t fit on

this one, given the offset and size of the other canvas.

@see replace! @see compose

# File lib/chunky_png/canvas/operations.rb, line 54
def compose!(other, offset_x = 0, offset_y = 0)
  check_size_constraints!(other, offset_x, offset_y)

  for y in 0...other.height do
    for x in 0...other.width do
      set_pixel(x + offset_x,
                y + offset_y,
                ChunkyPNG::Color.compose(other.get_pixel(x, y),
                                         get_pixel(x + offset_x,
                                                   y + offset_y)))
    end
  end
  self
end
crop(x, y, crop_width, crop_height) click to toggle source

Crops an image, given the coordinates and size of the image that needs to be cut out. This will leave the original image intact and return a new, cropped image with pixels copied from the original image.

@param [Integer] x The x-coordinate of the top left corner of the image

to be cropped.

@param [Integer] y The y-coordinate of the top left corner of the image

to be cropped.

@param [Integer] crop_width The width of the image to be cropped. @param [Integer] crop_height The height of the image to be cropped. @return [ChunkyPNG::Canvas] Returns the newly created cropped image. @raise [ChunkyPNG::OutOfBounds] when the crop dimensions plus the given

coordinates are bigger then the original image.
# File lib/chunky_png/canvas/operations.rb, line 150
def crop(x, y, crop_width, crop_height)
  dup.crop!(x, y, crop_width, crop_height)
end
crop!(x, y, crop_width, crop_height) click to toggle source

Crops an image, given the coordinates and size of the image that needs to be cut out.

This will change the size and content of the current canvas. Use {crop} if you want to have a new canvas returned instead, leaving the current canvas intact.

@param [Integer] x The x-coordinate of the top left corner of the image

to be cropped.

@param [Integer] y The y-coordinate of the top left corner of the image

to be cropped.

@param [Integer] crop_width The width of the image to be cropped. @param [Integer] crop_height The height of the image to be cropped. @return [ChunkyPNG::Canvas] Returns itself, but cropped. @raise [ChunkyPNG::OutOfBounds] when the crop dimensions plus the given

coordinates are bigger then the original image.
# File lib/chunky_png/canvas/operations.rb, line 170
def crop!(x, y, crop_width, crop_height)
  if crop_width + x > width
    raise ChunkyPNG::OutOfBounds, 'Original image width is too small!'
  end
  if crop_height + y > height
    raise ChunkyPNG::OutOfBounds, 'Original image height is too small!'
  end

  if crop_width == width && x == 0
    # We only need to crop off the top and/or bottom, so we can take a
    # shortcut.
    replace_canvas!(crop_width, crop_height,
                    pixels.slice(y * width, width * crop_height))
  else
    new_pixels = []
    for cy in 0...crop_height do
      new_pixels.concat pixels.slice((cy + y) * width + x, crop_width)
    end
    replace_canvas!(crop_width, crop_height, new_pixels)
  end
end
flip() click to toggle source
Alias for: flip_horizontally
flip!() click to toggle source
Alias for: flip_horizontally!
flip_horizontally() click to toggle source

Flips the image horizontally, leaving the original intact.

This will flip the image on its horizontal axis, e.g. pixels on the top will now be pixels on the bottom. Chaining this method twice will return the original canvas. This method will leave the original object intact and return a new canvas.

@return [ChunkyPNG::Canvas] The flipped image @see flip_horizontally!

# File lib/chunky_png/canvas/operations.rb, line 201
def flip_horizontally
  dup.flip_horizontally!
end
Also aliased as: flip
flip_horizontally!() click to toggle source

Flips the image horizontally in place.

This will flip the image on its horizontal axis, e.g. pixels on the top will now be pixels on the bottom. Chaining this method twice will return the original canvas. This method will leave the original object intact and return a new canvas.

@return [ChunkyPNG::Canvas] Itself, but flipped @see flip_horizontally

# File lib/chunky_png/canvas/operations.rb, line 214
def flip_horizontally!
  for y in 0..((height - 1) >> 1) do
    other_y   = height - (y + 1)
    other_row = row(other_y)
    replace_row!(other_y, row(y))
    replace_row!(y, other_row)
  end
  self
end
Also aliased as: flip!
flip_vertically() click to toggle source

Flips the image vertically, leaving the original intact.

This will flip the image on its vertical axis, e.g. pixels on the left will now be pixels on the right. Chaining this method twice will return the original canvas. This method will leave the original object intact and return a new canvas.

@return [ChunkyPNG::Canvas] The flipped image @see flip_vertically!

# File lib/chunky_png/canvas/operations.rb, line 236
def flip_vertically
  dup.flip_vertically!
end
Also aliased as: mirror
flip_vertically!() click to toggle source

Flips the image vertically in place.

This will flip the image on its vertical axis, e.g. pixels on the left will now be pixels on the right. Chaining this method twice will return the original canvas. This method will leave the original object intact and return a new canvas.

@return [ChunkyPNG::Canvas] Itself, but flipped @see flip_vertically

# File lib/chunky_png/canvas/operations.rb, line 249
def flip_vertically!
  for y in 0...height do
    replace_row!(y, row(y).reverse)
  end
  self
end
Also aliased as: mirror!
grayscale() click to toggle source

Converts the canvas to grayscale, returning a new canvas.

This method will not modify the canvas. To modift the current canvas, use {grayscale!} instead.

@return [ChunkyPNG::Canvas] A copy of the canvas, converted to

grayscale.

@see {grayscale!} @see {ChunkyPNG::Color#to_grayscale}

# File lib/chunky_png/canvas/operations.rb, line 34
def grayscale
  dup.grayscale!
end
grayscale!() click to toggle source

Converts the canvas to grayscale.

This method will modify the canvas. The obtain a new canvas and leave the current instance intact, use {grayscale} instead.

@return [ChunkyPNG::Canvas] Returns itself, converted to grayscale. @see {grayscale} @see {ChunkyPNG::Color#to_grayscale}

# File lib/chunky_png/canvas/operations.rb, line 20
def grayscale!
  pixels.map! { |pixel| ChunkyPNG::Color.to_grayscale(pixel) }
  self
end
mirror() click to toggle source
Alias for: flip_vertically
mirror!() click to toggle source
Alias for: flip_vertically!
replace(other, offset_x = 0, offset_y = 0) click to toggle source

Replaces pixels on this image by pixels from another pixels, on a given offset. This method will modify the current canvas.

This will completely replace the pixels of the background image. If you want to blend them with semi-transparent pixels from the foreground image, see {compose!}.

@param (see replace!) @return [ChunkyPNG::Canvas] Returns a new, combined canvas. @raise [ChunkyPNG::OutOfBounds] when the other canvas doesn’t fit on

this one, given the offset and size of the other canvas.

@note API changed since 1.0 - This method now no longer is in place,

but returns a new canvas and leaves the original intact. Use
{#replace!} if you want to replace pixels on the canvas in place.

@see compose

# File lib/chunky_png/canvas/operations.rb, line 133
def replace(other, offset_x = 0, offset_y = 0)
  dup.replace!(other, offset_x, offset_y)
end
replace!(other, offset_x = 0, offset_y = 0) click to toggle source

Replaces pixels on this image by pixels from another pixels, on a given offset. This method will modify the current canvas.

This will completely replace the pixels of the background image. If you want to blend them with semi-transparent pixels from the foreground image, see {compose!}.

@param [ChunkyPNG::Canvas] other The foreground canvas to get the

pixels from.

@param [Integer] offset_x The x-offset to apply the new foreground on. @param [Integer] offset_y The y-offset to apply the new foreground on. @return [ChunkyPNG::Canvas] Returns itself, but with the other canvas

placed onto it.

@raise [ChunkyPNG::OutOfBounds] when the other canvas doesn’t fit on

this one, given the offset and size of the other canvas.

@see compose! @see replace

# File lib/chunky_png/canvas/operations.rb, line 106
def replace!(other, offset_x = 0, offset_y = 0)
  check_size_constraints!(other, offset_x, offset_y)

  for y in 0...other.height do
    for d in 0...other.width
      pixels[(y + offset_y) * width + offset_x + d] = other.pixels[y * other.width + d]
    end
  end
  self
end
rotate_180() click to toggle source

Rotates the image 180 degrees.

This method will leave the original object intact and return a new canvas.

@return [ChunkyPNG::Canvas] The rotated image. @see rotate_180!

# File lib/chunky_png/canvas/operations.rb, line 318
def rotate_180
  dup.rotate_180!
end
rotate_180!() click to toggle source

Rotates the image 180 degrees in place.

@return [ChunkyPNG::Canvas] Itself, but rotated 180 degrees. @see rotate_180

# File lib/chunky_png/canvas/operations.rb, line 326
def rotate_180!
  pixels.reverse!
  self
end
rotate_clockwise() click to toggle source
Alias for: rotate_right
rotate_clockwise!() click to toggle source
Alias for: rotate_right!
rotate_counter_clockwise() click to toggle source
Alias for: rotate_left
rotate_counter_clockwise!() click to toggle source
Alias for: rotate_left!
rotate_left() click to toggle source

Returns an image that is rotated 90 degrees counter-clockwise.

This method will leave the original object intact and return a new canvas.

@return [ChunkyPNG::Canvas] A rotated copy of itself. @see rotate_left! for the in-place version.

# File lib/chunky_png/canvas/operations.rb, line 291
def rotate_left
  dup.rotate_left!
end
Also aliased as: rotate_counter_clockwise
rotate_left!() click to toggle source

Rotates the image 90 degrees counter-clockwise in place.

This method will change the original canvas. See {rotate_left} for a version that leaves the canvas intact and returns a new rotated canvas instead.

@return [ChunkyPNG::Canvas] Itself, but rotated.

# File lib/chunky_png/canvas/operations.rb, line 302
def rotate_left!
  new_pixels = []
  (width - 1).downto(0) { |i| new_pixels += column(i) }
  replace_canvas!(height, width, new_pixels)
end
Also aliased as: rotate_counter_clockwise!
rotate_right() click to toggle source

Returns a new canvas instance that is rotated 90 degrees clockwise.

This method will return a new canvas and leaves the original intact.

@return [ChunkyPNG::Canvas] A clockwise-rotated copy. @see rotate_right! for the in place version.

# File lib/chunky_png/canvas/operations.rb, line 265
def rotate_right
  dup.rotate_right!
end
Also aliased as: rotate_clockwise
rotate_right!() click to toggle source

Rotates the image 90 degrees clockwise in place.

This method will change the current canvas.

@return [ChunkyPNG::Canvas] Itself, but rotated clockwise. @see rotate_right for a version that leaves the current canvas intact

# File lib/chunky_png/canvas/operations.rb, line 275
def rotate_right!
  new_pixels = []
  0.upto(width - 1) { |i| new_pixels += column(i).reverse }
  replace_canvas!(height, width, new_pixels)
end
Also aliased as: rotate_clockwise!
trim(border = pixels.first) click to toggle source

Trims the border around the image, presumed to be the color of the first pixel.

@param [Integer] border The color to attempt to trim. @return [ChunkyPNG::Canvas] The trimmed image. @see trim!

# File lib/chunky_png/canvas/operations.rb, line 337
def trim(border = pixels.first)
  dup.trim!
end
trim!(border = pixels.first) click to toggle source

Trims the border around the image in place.

@param [Integer] border The color to attempt to trim. @return [ChunkyPNG::Canvas] Returns itself, but with the border

trimmed.

@see trim

# File lib/chunky_png/canvas/operations.rb, line 347
def trim!(border = pixels.first)
  x1 = [*0...width].index   { |c| column(c).uniq != [border] }
  x2 = [*0...width].rindex  { |c| column(c).uniq != [border] }
  y1 = [*0...height].index  { |r|    row(r).uniq != [border] }
  y2 = [*0...height].rindex { |r|    row(r).uniq != [border] }

  crop! x1, y1, x2 - x1 + 1, y2 - y1 + 1
end

Protected Instance Methods

check_size_constraints!(other, offset_x, offset_y) click to toggle source

Checks whether another image has the correct dimension to be used for an operation on the current image, given an offset coordinate to work with. @param [ChunkyPNG::Canvas] other The other canvas @param [Integer] offset_x The x offset on which the other image will be

applied.

@param [Integer] offset_y The y offset on which the other image will be

applied.

@raise [ChunkyPNG::OutOfBounds] when the other image doesn’t fit.

# File lib/chunky_png/canvas/operations.rb, line 391
def check_size_constraints!(other, offset_x, offset_y)
  if width  < other.width  + offset_x
    raise ChunkyPNG::OutOfBounds, 'Background image width is too small!'
  end
  if height < other.height + offset_y
    raise ChunkyPNG::OutOfBounds, 'Background image height is too small!'
  end
end