Re: Overlaying inline images

Bob Kanefsky (
Tue, 22 Nov 94 15:44:54 PST

>> The syntax might look something like this, as a strawman (or is that
>> "cohesively-challenged-person"?) proposal:
>> <Overlay IsMap>
>> <Image width=1000 height=1000 src="Big-Map.gif">
>> <Image width=120 height=120 src="Magnifying-glass-Stencil.gif"
>> x-offset=290 y-offset=590
>> <Image width=100 height=100 src="Closeup-of-20S-45W.gif"
>> x-offset=300 y-offset=600
>> </Overlay>

> David commented:

> [ what are TRANSPARENT and OPAQUE how are they defined, used, etc... ]

My intent was that some images have transparent areas that let the
previously-listed images show through. GIF89a has a mechanism for specifying
this, but all browsers I know of implement only the simple case where the
background shows through, not a second underlying image. In this example, the
magnifying glass would be annular -- just the frame would be opaque. The lens
would be transparent, letting the closeup show through. (Also, since images
are rectangular and magnifying glasses are round, the corners of the image,
outside the round frame, need to be transparent, letting the big map show

I probably didn't need to include explicit HTML keywords for TRANSPARENT and
OPAQUE, since the image itself can specify it. I was just trying to make the
intent more explicit by including as much as possible. Similarly, the width
and height are specified in the image, but I noticed that uses explicit dimensions (in their case, to allow
Mozilla to leave a blank space for the image so it can begin rendering the
text below it before even starting to download the image).

> I like this idea, there are some great potentials... But, I would think
> it would be better to make a "few" changes.

> <Viewport WIDTH=500 HEIGHT=200 BG=colorname ISMAP>
> <IMG XPOS=... YPOS=... SRC=... ALT=...>
> <IMG XPOS=... YPOS=... SRC=... ALT=...>
> <IMG XPOS=... YPOS=... SRC=... ALT=...>
> <ANNOTATE XPOS=... YPOS=...> text to render </ANNOTATE>
> </Viewport>
> [ this is very close to a GIF image file ]
> Instead of making an overlay are this is more of a drawport/viewport
> on an collection of images and graphics.

Fine with me. (BTW, "ALT" probably makes sense on Viewport than on IMG.)
If the term "viewport" also implies being able to display a subset of a
downloaded image, that would be even better; it would allow almost-smooth
scrolling because the whole image is cached on the local machine.

> This is similar to the other thread about graphing.

Sorry, I don't follow most of WWW-Talk, I just skim the archives occasionally
for relevant threads. I should take a look at that one sometime.

> ps. I don't remember what the FIG element is/was in HTML+, but
> I think there is some similarities here.

Here's a reference. If there's a later document somewhere, I don't know about it.
It doesn't seem to support overlaying anything over the figure, just wrapping
text around it and typesetting a caption near it.

                      --Bob Kanefsky (Recom Technologies)
                        Computational Sciences Division
                        NASA Ames Research Center
                        Mars Atlas: