DOCBOOK: A proposal to clarify the semantics of DocBook graphics

[Norman Walsh <ndw@nwalsh.com>]

Proposal: http://sourceforge.net/docman/display_doc.php?docid=9357&group_id=21935

DocBook graphic elements have four attributes that relate to the size of
the image: width, depth, scale, and scalefit. Recent list traffic, some
offline conversations, and a bit of thought have convinced me that this
simply isn't sufficient.

I propose that we add four additional attributes to DocBook graphic
elements: content-width, content-depth, align, and valign. The resulting
DocBook semantics would be:

width
        Specifies the width of the area in which the image will be
        displayed (the reproduction area or viewport width). If
        unspecified, the default value is implementation defined.

content-width
        Specifies the width of the actual image before scaling factors are
        applied. If unspecified, the default value is the natural width of
        the image. If the processor cannot determine the natural width of
        the image, the results are implementation defined.

depth
        Specifies the depth (height) of the area in which the image will
        be displayed (the reproduction area or viewport depth). If
        unspecified, the default value is implementation defined.

content-depth
        Specifies the depth (height) of the actual image before scaling
        factors are applied. If unspecified, the default value is the
        natural depth of the image. If the processor cannot determine the
        natural depth of the image, the results are implementation
        defined.

scale
        Specifies a scaling factor for the image, expressed as a
        percentage. A value of 50 expresses a scaling factor of 50%.
        Scaling is applied to the content-width and content-height
        uniformly. If the post-scaled dimension of the image exceeds the
        specified reproduction area size in that dimension, the results
        are implementation defined. If both scale and scalefit are
        specified, scale is ignored.

scalefit
        Specifies that the image should be scaled to fit within the
        specified height and width. Scaling is applied so that one
        dimension fits exactly and the other is entirely within the
        reproduction area. Unless the image dimensions are in the same
        proportion as the reproduction area dimensions, the image will be
        smaller than the reproduction area in one dimension. If both scale
        and scalefit are specified, scale is ignored.

align
        If the scaled content size is narrower than the specified width,
        the image will be aligned within the width according to this value
        (one of "left", "center", or "right").

valign
        If the scaled content size is shorter than the specified depth,
        the image will be aligned within the depth according to this value
        (one of "top", "middle", or "bottom").

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com>      | Is your cucumber bitter? Throw it
http://www.oasis-open.org/docbook/ | away. Are there briars in your
Chair, DocBook Technical Committee | path? Turn aside. That is enough.
                                   | Do not go on to say, 'Why were
                                   | things of this sort ever brought
                                   | into the world?'--Marcus Aurelius