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
362 def border(size, color = ChunkyPNG::Color::BLACK)
363   dup.border!(size, color)
364 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
372 def border!(size, color = ChunkyPNG::Color::BLACK)
373   new_width  = width  + size * 2
374   new_height = height + size * 2
375 
376   bg = Canvas.new(new_width, new_height, color).replace(self, size, size)
377   replace_canvas!(new_width, new_height, bg.pixels)
378 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
85 def compose(other, offset_x = 0, offset_y = 0)
86   dup.compose!(other, offset_x, offset_y)
87 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
54 def compose!(other, offset_x = 0, offset_y = 0)
55   check_size_constraints!(other, offset_x, offset_y)
56 
57   for y in 0...other.height do
58     for x in 0...other.width do
59       set_pixel(x + offset_x,
60                 y + offset_y,
61                 ChunkyPNG::Color.compose(other.get_pixel(x, y),
62                                          get_pixel(x + offset_x,
63                                                    y + offset_y)))
64     end
65   end
66   self
67 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
150 def crop(x, y, crop_width, crop_height)
151   dup.crop!(x, y, crop_width, crop_height)
152 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
170 def crop!(x, y, crop_width, crop_height)
171   if crop_width + x > width
172     raise ChunkyPNG::OutOfBounds, 'Original image width is too small!'
173   end
174   if crop_height + y > height
175     raise ChunkyPNG::OutOfBounds, 'Original image height is too small!'
176   end
177 
178   if crop_width == width && x == 0
179     # We only need to crop off the top and/or bottom, so we can take a
180     # shortcut.
181     replace_canvas!(crop_width, crop_height,
182                     pixels.slice(y * width, width * crop_height))
183   else
184     new_pixels = []
185     for cy in 0...crop_height do
186       new_pixels.concat pixels.slice((cy + y) * width + x, crop_width)
187     end
188     replace_canvas!(crop_width, crop_height, new_pixels)
189   end
190 end
flip()
Alias for: flip_horizontally
flip!()
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
201 def flip_horizontally
202   dup.flip_horizontally!
203 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
214 def flip_horizontally!
215   for y in 0..((height - 1) >> 1) do
216     other_y   = height - (y + 1)
217     other_row = row(other_y)
218     replace_row!(other_y, row(y))
219     replace_row!(y, other_row)
220   end
221   self
222 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
236 def flip_vertically
237   dup.flip_vertically!
238 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
249 def flip_vertically!
250   for y in 0...height do
251     replace_row!(y, row(y).reverse)
252   end
253   self
254 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
34 def grayscale
35   dup.grayscale!
36 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
20 def grayscale!
21   pixels.map! { |pixel| ChunkyPNG::Color.to_grayscale(pixel) }
22   self
23 end
mirror()
Alias for: flip_vertically
mirror!()
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
133 def replace(other, offset_x = 0, offset_y = 0)
134   dup.replace!(other, offset_x, offset_y)
135 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
106 def replace!(other, offset_x = 0, offset_y = 0)
107   check_size_constraints!(other, offset_x, offset_y)
108 
109   for y in 0...other.height do
110     for d in 0...other.width
111       pixels[(y + offset_y) * width + offset_x + d] = other.pixels[y * other.width + d]
112     end
113   end
114   self
115 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
318 def rotate_180
319   dup.rotate_180!
320 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
326 def rotate_180!
327   pixels.reverse!
328   self
329 end
rotate_clockwise()
Alias for: rotate_right
rotate_clockwise!()
Alias for: rotate_right!
rotate_counter_clockwise()
Alias for: rotate_left
rotate_counter_clockwise!()
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
291 def rotate_left
292   dup.rotate_left!
293 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
302 def rotate_left!
303   new_pixels = []
304   (width - 1).downto(0) { |i| new_pixels += column(i) }
305   replace_canvas!(height, width, new_pixels)
306 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
265 def rotate_right
266   dup.rotate_right!
267 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
275 def rotate_right!
276   new_pixels = []
277   0.upto(width - 1) { |i| new_pixels += column(i).reverse }
278   replace_canvas!(height, width, new_pixels)
279 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
337 def trim(border = pixels.first)
338   dup.trim!
339 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
347 def trim!(border = pixels.first)
348   x1 = [*0...width].index   { |c| column(c).uniq != [border] }
349   x2 = [*0...width].rindex  { |c| column(c).uniq != [border] }
350   y1 = [*0...height].index  { |r|    row(r).uniq != [border] }
351   y2 = [*0...height].rindex { |r|    row(r).uniq != [border] }
352 
353   crop! x1, y1, x2 - x1 + 1, y2 - y1 + 1
354 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
391 def check_size_constraints!(other, offset_x, offset_y)
392   if width  < other.width  + offset_x
393     raise ChunkyPNG::OutOfBounds, 'Background image width is too small!'
394   end
395   if height < other.height + offset_y
396     raise ChunkyPNG::OutOfBounds, 'Background image height is too small!'
397   end
398 end