[R] Artifacts in pdf() of image() (w/o comments)

[Duncan Murdoch]

Michael Kubovy wrote:
> On Aug 12, 2007, at 6:24 AM, Duncan Murdoch wrote:
>
>   
>> Michael Kubovy wrote:
>>     
>>> Dear r-helpers,
>>>
>>> In my previous message there were comments in the code that may  
>>> have  made cutting and pasting awkward. Here it is w/o them.
>>>
>>> I have two questions:
>>>
>>> (1) The following produces a pdf with artifacts. How do I prevent  
>>> them?
>>>
>>>       
>> What artifacts do you see?  It looks like a smoothly varying field  
>> when produced by R 2.5.1 and viewed in Acrobat Reader 6.0 on Windows.
>>
>> Duncan Murdoch
>>     
>>> require(grDevices)
>>> imSize <- 200
>>> lambda <- 10
>>> theta <- 15
>>> sigma <- 40
>>> x <- 1:imSize
>>> x0 <- x / imSize -.5
>>> freq = imSize/lambda
>>> xf = x0 * freq * 2 * pi
>>> f <- function(x, y){r <- -((x^2 + y^2)/(sigma ^2)); exp(r)}
>>> z <- outer(xf, xf, f)
>>> f1 <- function(x, y){cos(.1 * x)}
>>> z1 <- outer(xf, xf, f1)
>>> pdf('gabor.pdf')
>>> image(xf, xf, z * z1, col = gray(250:1000/1000),
>>> xlab = '', ylab =  '', bty = 'n', axes = FALSE, asp = 1)
>>> dev.off()
>>>       
>
> I'm working on a Mac. You're right, Acrobat 6.05 renders the figure  
> nicely, but when it's included in a LaTeX-produced pdf or viewed with  
> the Mac Preview program, a grid of fine white lines is superimposed  
> on the figure. So I believe that it's a matter of aliasing, which I  
> might be able to prevent by adjusting the parameters of the figures.  
> I just don't know enough to figure this out, and would appreciate  
> guidance.
I see the artifacts in Preview on a Mac too.  So it looks to me like a 
Mac bug.

Preview is actually pretty poor at graphics display; see 
<http://www.geuz.org/pipermail/gl2ps/2007/000223.html>.

My only suggestion is not to use Preview.

Duncan Murdoch