Overlapping lines appearing thicker

[Karl Kuehn]

I am new to this list, so my apologies if any of this has been covered 
before...
	I too am having the problem with overlapping lines, but I think I 
might know what is going on. I remember a conversation over on 
macosx-dev about this same sort of thing when drawing lines that didn't 
line up exactly with the pixel grid in an anti-aliased view. Since the 
line did not belong to either one pixel or another, both would get a 
percentage of the color-weight. This looks fine when you only have one 
line, but starts to add up when you have more than one line on top of 
another, making it eventually look like there are a couple of lines 
next to each other. This looks exactly like the problem I have been 
battling with.
	The reason that this also affects tiffs (it does not affect vector 
formats like PDF) is that CoreGraffics method to convert to tiffs just 
rasterizes the image as it is. If you could bump up the DPI some, the 
problem starts to go away. I am putting up some example images on the 
web to show:

A Screenshot showing that we are off the guide line (and off pixel):
	http://valleybyowner.dyndns.info/~larkost/OGProblem/screenshot.pdf

The problem at 72dpi in tiff:
	http://valleybyowner.dyndns.info/~larkost/OGProblem/problem72dpi.tiff

And the partial fix at 200dpi tiff:
	http://valleybyowner.dyndns.info/~larkost/OGProblem/problem200dpi.tiff

Finally the correct image in PDF:
	http://valleybyowner.dyndns.info/~larkost/OGProblem/correct.pdf

(Ps.. sorry about the size of the tiffs, but I don't have PhotoShop on 
this computer, and so don't have zip compression in tiffs)

	There is a way of partially fighting this (workaround), and that is to 
put extra points along the line and make sure that these points snap to 
grid (and thus to pixels). This is also the answer to Tim's second 
question about how to route lines. You just Option-Double-Click (or if 
you have played with the preferences just Double-Click) on the line in 
question, and you have a point to move around. This does have the 
down-side that things get a bit messy when you are moving object around 
and the point you put down stay where they are put. And there is the 
problem that you have to do this for every line that crosses over the 
same area. Plus when you want to move this group of lines you have to 
move each point at a time as there is no way of grabbing a bunch of 
points on different object at a time (instead it grabs the objects 
themselves).
	But this work-around does not solve everything, because it does not 
work with magnets on objects. They can still be off-pixel, and any 
lines connecting to them will have to be off-pixel.

Now, here are my ideas for solutions in future version of OG:

	Allow for a setting that would force all lines and magnets to snap to 
the pixel. This could either be done at the positioning level (so that 
things would really always be in 1/72 of an inch increments), or could 
be done at the rendering level (so things just looked that way on 
screen). I would vote for the rendering level.

	Add a "Cable Ties" object that would act like a magnet for lines, 
grouping them together. This way you could string a whole bunch of 
lines together and then set the "Cable Tie" to snap to grid and you 
would have  fixed the problem at hand without having to add points to 
every line individually. The other nice thing about this is that if you 
then moved the "Cable Ties" than the lines would all move at the same 
time. For bonus points the "Cable Ties" could optionally separate 
different styles of lines into different groups (so that they would be 
parallel lines... maybe separated by pixels... *hint* *hint*).
	The biggest difficulty I would foresee would be the UI to separate 
lines from the "Cable Ties". My thought on this (I seem to have a few, 
no?) would be to have a magnified view pop up when you click on the 
"Cable Tie". Then you could drag a line out of the group. This would 
require some way of grabbing lines by arbitrary points (which might be 
nice anyways....).

	Allow magnets to snap to grid in the magnet editor. Right now it is 
really difficult to get them to line up properly. If when setting 
magnet positions you could set a point on the object that could be the 
snap-to point for alignment purposes. Obviously the snap-to would also 
have to gravitate to the edges. As a side note, I would like the option 
to confine the magnets to the drawn edges of groups rather than the 
bounding box of the group (or even better, allow for object to be 
inside another... but that is another more complex request).

	Ok... I think that is enough of War-and-Peace....

		Karl Kuehn
			larkost at softhome.net

On Jan 8, 2004, at 2:39 AM, Tim Ryan wrote:

> I agree with Jens on this - in fact, the behaviour of lines in general 
> is
> the biggest area I have issues with Omnigraffle. We run a web design
> company, so appearance is critical, even if we are presenting a site
> structure diagram to clients.
>
> I don't like:
> 1) Overlapping lines, even when they are connected to the same magnet
> 2) The automatic routing of lines - I would like some way of fixing the
> route of a line within a diagram (eg to avoid clashing with other 
> elements)
> rather than simply specifying a start and end point)