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
364 def border(size, color = ChunkyPNG::Color::BLACK)
365   dup.border!(size, color)
366 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
374 def border!(size, color = ChunkyPNG::Color::BLACK)
375   new_width  = width  + size * 2
376   new_height = height + size * 2
377 
378   bg = Canvas.new(new_width, new_height, color).replace(self, size, size)
379   replace_canvas!(new_width, new_height, bg.pixels)
380 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
88 def compose(other, offset_x = 0, offset_y = 0)
89   dup.compose!(other, offset_x, offset_y)
90 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(
60         x + offset_x,
61         y + offset_y,
62         ChunkyPNG::Color.compose(
63           other.get_pixel(x, y),
64           get_pixel(x + offset_x, y + offset_y)
65         )
66       )
67     end
68   end
69   self
70 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
153 def crop(x, y, crop_width, crop_height)
154   dup.crop!(x, y, crop_width, crop_height)
155 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
173 def crop!(x, y, crop_width, crop_height)
174   if crop_width + x > width
175     raise ChunkyPNG::OutOfBounds, "Original image width is too small!"
176   end
177   if crop_height + y > height
178     raise ChunkyPNG::OutOfBounds, "Original image height is too small!"
179   end
180 
181   if crop_width == width && x == 0
182     # We only need to crop off the top and/or bottom, so we can take a
183     # shortcut.
184     replace_canvas!(crop_width, crop_height, pixels.slice(y * width, width * crop_height))
185   else
186     new_pixels = []
187     for cy in 0...crop_height do
188       new_pixels.concat pixels.slice((cy + y) * width + x, crop_width)
189     end
190     replace_canvas!(crop_width, crop_height, new_pixels)
191   end
192 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
203 def flip_horizontally
204   dup.flip_horizontally!
205 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
216 def flip_horizontally!
217   for y in 0..((height - 1) >> 1) do
218     other_y   = height - (y + 1)
219     other_row = row(other_y)
220     replace_row!(other_y, row(y))
221     replace_row!(y, other_row)
222   end
223   self
224 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
238 def flip_vertically
239   dup.flip_vertically!
240 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
251 def flip_vertically!
252   for y in 0...height do
253     replace_row!(y, row(y).reverse)
254   end
255   self
256 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
136 def replace(other, offset_x = 0, offset_y = 0)
137   dup.replace!(other, offset_x, offset_y)
138 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
109 def replace!(other, offset_x = 0, offset_y = 0)
110   check_size_constraints!(other, offset_x, offset_y)
111 
112   for y in 0...other.height do
113     for d in 0...other.width
114       pixels[(y + offset_y) * width + offset_x + d] = other.pixels[y * other.width + d]
115     end
116   end
117   self
118 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
320 def rotate_180
321   dup.rotate_180!
322 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
328 def rotate_180!
329   pixels.reverse!
330   self
331 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
293 def rotate_left
294   dup.rotate_left!
295 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
304 def rotate_left!
305   new_pixels = []
306   (width - 1).downto(0) { |i| new_pixels += column(i) }
307   replace_canvas!(height, width, new_pixels)
308 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
267 def rotate_right
268   dup.rotate_right!
269 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
277 def rotate_right!
278   new_pixels = []
279   0.upto(width - 1) { |i| new_pixels += column(i).reverse }
280   replace_canvas!(height, width, new_pixels)
281 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
339 def trim(border = pixels.first)
340   dup.trim!
341 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
349 def trim!(border = pixels.first)
350   x1 = [*0...width].index   { |c| column(c).uniq != [border] }
351   x2 = [*0...width].rindex  { |c| column(c).uniq != [border] }
352   y1 = [*0...height].index  { |r|    row(r).uniq != [border] }
353   y2 = [*0...height].rindex { |r|    row(r).uniq != [border] }
354 
355   crop! x1, y1, x2 - x1 + 1, y2 - y1 + 1
356 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
393 def check_size_constraints!(other, offset_x, offset_y)
394   if width < other.width + offset_x
395     raise ChunkyPNG::OutOfBounds, "Background image width is too small!"
396   end
397   if height < other.height + offset_y
398     raise ChunkyPNG::OutOfBounds, "Background image height is too small!"
399   end
400 end