class

StumpyCore::Canvas

Inherits Reference < Object

A canvas is 2D array of RGBA pixels

To create a canvas of size 400 x 200

canvas = StumpyCore::Canvas.new(400, 200)

The default background color is transparent, but it can be passed in as a parameter or as a block that returns the color value for each {x, y} pair.

canvas2 = StumpyCore::Canvas.new(400, 200, RGBA::WHITE)

canvas3 = StumpyCore::Canvas.new(256, 256) do |x, y|
  RGBA.from_rgb_n(x, y, 255, 8)
end

Because of the way pixels are stored in a Slice, Canvases are limited to Int32::MAX = 2147483647 pixels in total, e.g. a maximal size of 46340x46340 for a square image.

Constructors

new(width : Int32, height : Int32, background = RGBA.new(0_u16, 0_u16, 0_u16, 0_u16))

new(width : Int32, height : Int32, &)

Instance methods

==(other)

Two canvases are considered equal if they are of equal size and all their pixels are equal

[](x, y)

Short form for get

[]=(x, y, color)

Short form for set

each_row

Iterate over each row of the canvas (a Slice(RGBA) of size @width). The main usecase for this is writing code that encodes images in some file format.

get(x, y)

Get the value of pixel (x, y) without checking if (x, y) is a valid position.

height

includes_pixel?(x, y)

Check if pixel (x, y) is part of this canvas.

map

Same as map!, but instead of mutating the current canvas, a new one is created and returned

map!

Modify pixels by applying a function (color, x, y) -> new_color to each pixel of the current canvas, e.g. to invert colors

map_with_index

Same as map but passes along a fourth parameter with the index in the pixels slice

map_with_index!

Same as map! but passes along a fourth parameter with the index in the pixels slice

paste(canvas : Canvas, x, y)

Past the contents of a second Canvas into this one, starting at position (x, y). The pixels are combined using the RGBA#over function.

pixels

safe_get(x : Int32, y : Int32) : RGBA | Nil

Same as get, but returns nil if (x, y) are outside of the canvas

safe_set(x : Int32, y : Int32, color : RGBA) : Bool

Same as set, but only sets the pixel, if it is part of the canvas. Returns true if the pixel was set successfully, false if it was outside of the canvas.

set(x, y, color)

Set the value of pixel (x, y) to color without checking if (x, y) is a valid position.

width

wrapping_get(x : Int32, y : Int32) : RGBA

Same as get, but if x ore y are outside of the canvas, wrap them over at the edges. E.g. wrapping_get(300, 250) on a 200x200 canvas returns the pixel at (100, 50).

wrapping_set(x : Int32, y : Int32, color : RGBA)

Same as set, but wrapping along the canvas edges. See wrapping_get for an example.