png() and image()
By changing
png("large.png", height=nrow(z), width=ncol(z), bg="red")
to
png("large.png", height=nrow(z), width=ncol(z), bg="blue")
I can get the right column (on linux) to change to blue.
So it seems to be an alignment off-by-one error with the background
colour showing through, so you might be able to work around it
by changing the alignment of the margins.
Incidentally I am working on the AffyMetrix 500k chip as well
(http://www.wtccc.org.uk/) but I have already written a non-R C/C++
tool to dump all the probe signal of a whole array as an image
(not intended for html, obviously, for 6.5 million probes); and
another one for drawing the schematics of the locations of
probes associated with a specific snp as a postscript vector diagram.
I will probably be working on combining the two - i.e. overlaying
an image with a vector diagram next week. (which means I hope to get
an image of intensities with some cicles on top, highlighting the
effect on the intensities to a specific snp due to blemishes).
Hin-Tak Leung
Henrik Bengtsson wrote:
Hi,
I try to create PNG images of a certain size where each pixel
intensity corresponds to exactly one probe signal in an Affymetrix
array. I try to use png() and image() with zero margins to do this.
Example:
z <- matrix(1:15, nrow=45, ncol=30)
png("large.png", height=nrow(z), width=ncol(z), bg="red")
par(mar=c(0,0,0,0))
image(z, col=gray.colors(16), axes=FALSE)
dev.off()
z <- matrix(1:15, nrow=5, ncol=3)
png("tiny.png", height=nrow(z), width=ncol(z), bg="red")
par(mar=c(0,0,0,0))
image(z, col=gray.colors(16), axes=FALSE)
dev.off()
The problem is that on WinXP the very bottom row and the very right
column of pixels in red. Trying on Linux, it is only the very right
column that is red. See attached images (you might have to zoom in to
see it). I try to do this in R v2.3.1. The same effect is seen if
the jpeg() device is used.
When rescaling, the same effect is seen (the red border effect is one
pixel wide), e.g.
z <- matrix(1:15, nrow=45, ncol=30)
png("large5.png", height=5*nrow(z), width=5*ncol(z), bg="red")
par(mar=c(0,0,0,0))
image(z, col=gray.colors(16), axes=FALSE)
dev.off()
I might be asking for something that is not supported, but is there a
way around this? It is a problem, because I wish to tile the images
in an HTML page.
Thanks
Henrik
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