The effect Duncan's picture shows is typical of using anti-aliasing for
rectangles and polygons. The cairo-based devices have it turned off for
filled regions, as it seems to have no advantage for R uses of such
regions. (You also see it with some on-screen renderers of postscript or
pdf versions of this plot, e.g. those based on ghostscript.)
However, this does not match the original report, so I think we need a
reproducible example (with screenshot) from Joseph Scandura to make any
further progress.
On Wed, 21 May 2008, Duncan Murdoch wrote:
(Edited to add link to sample picture)
Simon Urbanek wrote:
On May 20, 2008, at 8:05 PM, [EMAIL PROTECTED] wrote:
Full_Name: Joseph Scandura
Version: 2.7.0
OS: Mac 10.5
Submission from: (NULL) (140.251.50.94)
Since updating to 2.7.0 all plots that use image() (heatmap, etc...)
now draw visible boxes around each rectangle in the plot. When there
are many rectangles the surrounding color becomes dominant over the
rectangle color and the overall image is borderline useless.
Can you, please, specify exactly which graphics device you are using and
possibly a snapshot of the problem? I don't see any additional boxes being
drawn on any device.
I see lines at the borders of the grid used by image on my Mac (Tiger, R
2.7.0 Patched (2008-05-20 r45743)).
They are most visible in the last of the examples plotted by
example(image), the one that starts
image(x, y, volcano, col = terrain.colors(100), axes = FALSE). It opens
a Quartz device.
How do you do a snapshot on a Mac? I see online that it's Cmd-Shift-4,
and I get the snapshot click, but I don't know where the picture ended up.
AHA! It goes to the desktop.
Okay, a sample picture is available at
http://www.stats.uwo.ca/faculty/murdoch/temp/grid.png
Not as bad as Joseph was describing, but not nearly as good as Windows
produces ;-).
The only issue I'm aware of are anti-aliasing effects around the edges of
adjacent rectangles which don't fall on the pixel boundary (if anti-
aliasing device is used). Depending on the subpixel location of the edge,
the background color may shine through very slightly. It's not what you
describe, but it's closest to what I can imagine you could mean. However,
AFAICS this has not been changed recently and is a rendering artifact
which is hard to get rid of in the current setup as devices are
resolution-independent (the only cure I'm aware of [short of disabling
anti-aliasing] is to distort the original plot such that rectangles are
aligned with the pixels of the output medium).
I don't know if what I'm seeing is new or not; I've only got one R
version installed.
Duncan Murdoch
Cheers,
Simon
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--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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