|=  dim=@ud
^-  @ux
:: Pixel bytes for 24bpp dim*dim image
:: Note: this calculation does not support padding, so dim%4 must be 0
::
=/  datasize=@  (mul 3 (mul dim dim))
:: The header is a list of [bytes, value] to be composed into a single blob
::
=/  header=@
   %+  can  3
    ^-  (list [@ @])
    :~
        :: BMP header part, 14 bytes
        ::
        [2 'BM']               :: format ID
        [4 (add 54 datasize)]  :: file size - 54 byte header + pixel data
        [4 0]                  :: unused
        [4 54]                 :: header size
        :: DIB header part, 4 bytes
        ::
        [4 40]                 :: DIB header size
        [4 dim]                :: width
        [4 dim]                :: height
        [2 3]                  :: number of channels
        [2 24]                 :: bits per pixel
        [4 0]                  :: compression (none; BI_RGB)
        [4 datasize]           :: pixel data size
        [4 2.835]              :: print resolution x (72 DPI)
        [4 2.835]              :: print resolution y (72 DPI)
        [8 0]                  :: palette stuff (unused)
    ==
=/  image=@
    %+  rap  3
    =/  py=@  0
    |-
    ^-  (list @)
    =/  px=@  0
    |-
    ^-  (list @)
    :: Define the image as a BGR888 pixel in terms of x and y
    ::
    :-  (add 128 (div (mul px 256) (mul 2 dim)))
    :-  255
    :-  255
    :: Recurse for all pixels
    ::
    ?:  (lth +(px) dim)
        $(px +(px))
    ?:  (lth +(py) dim)
        ^$(py +(py))
    ~
%+  can  3
^-  (list [@ @])
:~
    [54 header]
    [datasize image]
==