grayscale

Builtin index · Images

result = grayscale(img)

Input: img · Output: result

What it is

img is an Image of any size. Converts RGB → luma via ITU-R BT.601 weights (matches plotting.rs's contrast_text_color).

Overloads

One call shape — this function is not overloaded.

Code	Input	Output	Description
`result = grayscale(img)`	`img` Imagenot documented yet	`result` Image	Returns a new `Image`, same width/height as `img`, with R=G=B at every pixel — still a full 3-channel RGB image, not a separate 1-channel type.

Examples

From the documentation, and run by the build -- the output and the figure below are what the engine actually produced. Simplest first.

img = load_image("sample.bmp")
edges = edge_detect(grayscale(img))
imshow(edges)

from images

# A gradient with a bright bar in it, so the rotation below is visible:

# a symmetric test image would look identical afterwards.

n = 48
g = zeros(n, n)
for i in 0 to n - 1
    for j in 0 to n - 1
        g[i, j] = 40 + 3 * j
        if i > 10 and i < 22 and j > 6 and j < 30
            g[i, j] = 240
        end if
    end for
end for
save_image("sample.bmp", image_from_matrix(g))

img = load_image("sample.bmp")
gray = grayscale(img)
imshow(gray)

from images

How it works

grayscale(img) — RGB -> luma via ITU-R BT.601 weights (see image::Image::to_grayscale's doc comment for why BT.601 over contrast_text_color, which already uses these exact weights). Returns a full RGB image with R=G=B, not a separate 1-channel type.

From the note above this builtin in the interpreter, where the reasoning was written down as it was built.