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From: ImageAnalyst <imageanalyst@mailinator.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: image overlay
Date: Mon, 19 May 2008 11:02:36 -0700 (PDT)
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On May 19, 12:57=A0pm, "jay vaughan" <jvaughan5.nos...@gmail.com> wrote:
> Thought I would try a second time to see if anyone has ideas
> about an image overlay at the screen resolution... thanks.
>
> J

---------------------------------------
If you're just plotting an outline, you can use the plot() function
which will plot it as a smooth vector that I don't believe will show
the big quantized blocky pixels when you zoom way in.  Can you get the
perimeter of the blob, then scale the numbers, then using poly2mask()
convert it to a bitmap with the higher resolution.  This should
produce a smoother boundary because you're basically using the vector-
based boundary to create a higher resolution bitmap.

If you're displaying a pixel-based image, you're out of luck.  You
could resample at a higher res but then whatever you did to create the
overlay will still be blocky, unless you do something else like
resample higher and then blur it.  That would get you a smoother
overlay but it's no more accurate than the original image in which
pixels got selected for the overlay image, in fact it's less accurate
so don't fool yourself.  It's smoother but only because you're making
up intermediate pixels values and locations to get that smoother
boundary.  Since you're making up pixels that weren't in your original
image, there's no guarantee that the boundary on your processed image
would correspond better to the image as if you HAD started out with
the higher resolution on the original image than if you just used the
blocky one.
Regards,
ImageAnalyst