postscript image problem (PR#6763)

Hi


 

Full_Name: Jonathan Lees
I am having trouble with the postscript output of images.
They have lines on them that are not supposed to be there.
I have noticed this on numerous trials of printing various images.
I looked at the postscript and I see that it
appears to plot each individual block - so perhaps occasionally the 
space between the blocks "leaks" through do to round off,
thus contaminating the image.
this could be solved if the image software used postscript
image plotting functions.

Here is an example of some code:

postscript(file ="test.ps" , onefile=FALSE, print.it=FALSE)


w<-5 #width of central square
m=w
xn<- 128; yn<- 128
im<- matrix(0,nrow=yn,ncol=xn)
xc<-floor(xn/2)+1;
yc<- floor(yn/2)+1 # centers of the image
im[(-m:m)+xc,(-m:m)+yc]<- 1

image(im , col = cmap ); title('im=Original image')


dev.off()

view this output with any postscript viewer (or printer)
and you will see extra lines on the plot.
   

Is this just caused by antialiasing on the postscript viewer.  I see this with
anti-aliasing on, but it goes away if I turn antialiasing off.  Of course, that
wouldn't explain the effect when a document is printed, but I don't get that.

Paul