> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/g/grayscale_image.md).

# Grayscale image

```ruby
require('Image::Imlib2')

func tograyscale(img) {
    var (width, height) = (img.width, img.height)
    var gimg = %O<Image::Imlib2>.new(width, height)
    for y,x in (^height ~X ^width) {
        var (r, g, b) = img.query_pixel(x, y)
        var gray = int(0.2126*r + 0.7152*g + 0.0722*b)
        gimg.set_color(gray, gray, gray, 255)
        gimg.draw_point(x, y)
    }
    return gimg
}

var (input='input.png', output='output.png') = ARGV...
var image = %O<Image::Imlib2>.load(input)
var gscale = tograyscale(image)
gscale.set_quality(80)
gscale.save(output)
```