77 lines
3.1 KiB
Lua
77 lines
3.1 KiB
Lua
 
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-- Copyright (c) 2026 Marc Wäckerlin. SPDX-License-Identifier: MIT
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-- A picture that stands alone in its paragraph gets its caption under it.
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--
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-- `` carries a text between the brackets, and
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-- every reader who writes it means it as the caption. GFM has no such rule: the
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-- text becomes the alternative text of the picture, which reaches a screen
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-- reader and nobody else, and the PDF shows a picture with nothing under it.
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--
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-- pandoc has the rule under the name implicit_figures, and its GFM reader does
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-- not carry it, so the paragraph is turned into a figure here. What the figure
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-- then looks like — where it stands, how the caption is set — comes from the
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-- package like everything else.
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-- A picture that stands directly under a heading does not float away from it.
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--
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-- A floating picture leaves the page it was written on, and where the heading
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-- announced nothing but that picture, the heading stays behind alone at the
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-- foot of the page. Measured over one report: a page ended with its heading,
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-- 430 points of it still empty, and its picture began on the next. The
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-- reservation a heading takes cannot answer this — the room was there, and what
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-- should have filled it had left the page.
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--
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-- So this one picture is placed where it stands. It then either fits under its
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-- heading, or the page breaks BEFORE the heading and the two travel together,
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-- which is what a reader expects of a heading.
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local function nailed(figure)
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return {
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pandoc.RawBlock('latex', '\\begingroup\\floatplacement{figure}{H}'),
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figure,
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pandoc.RawBlock('latex', '\\endgroup'),
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}
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end
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function Blocks(blocks)
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if not FORMAT:match('latex') then return nil end
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local kept, previous = pandoc.Blocks{}, nil
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for _, block in ipairs(blocks) do
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if block.t == 'Figure' and previous and previous.t == 'Header' then
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for _, piece in ipairs(nailed(block)) do
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kept:insert(piece)
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end
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else
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kept:insert(block)
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end
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previous = block
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end
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return kept
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end
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-- A picture of pixels says so, because only this side knows the file name.
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--
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-- How large a picture may be drawn is the package's rule, and it is not the
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-- same rule for a drawing and for a photograph: a drawing is drawn again at
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-- every size, a raster of pixels gets coarse. What the package sees is the
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-- finished box, which carries no file name any more, so the mark is set here
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-- and read by the picture that follows it.
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local RASTER = {
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png = true, jpg = true, jpeg = true, bmp = true,
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gif = true, tif = true, tiff = true,
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}
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function Image(image)
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if not FORMAT:match('latex') then return nil end
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local extension = image.src:match('%.([%a%d]+)$')
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if extension and RASTER[extension:lower()] then
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return { pandoc.RawInline('latex', '\\businessbitmap'), image }
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end
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end
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function Para(para)
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if #para.content ~= 1 then return nil end
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local image = para.content[1]
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if image.t ~= 'Image' or #image.caption == 0 then return nil end
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return pandoc.Figure(
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pandoc.Blocks{ pandoc.Plain{ image } },
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{ long = pandoc.Blocks{ pandoc.Plain(image.caption) } })
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end
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