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Re: Label_region and Erosion [message #13356 is a reply to message #13283]

Fri, 06 November 1998 00:00

Struan Gray
Messages: 178
Registered: December 1995

Senior Member

Alex Schuster, alex@rosa.mpin-koeln.mpg.de writes:
>
> Struan Gray wrote:
>>
>> mask = image > threshold_val
>
> Slight correction: mask = image gt threshold_val

Sigh. I made this mistake in my very first programming class and
have been making it consistently ever since. Thanks for pointing it
out.

While I'm here, another thing I like to do when using masks is to
display the mask as a colour cast on the original image by creating an
RGB image and zeroing one of the channels wherever the mask is active:

image = byte(dist(250))
mask = image gt 100
rgb_image = bytarr(3,250,250)
rgb_image[0,*,*] = image*(mask eq 0)
rgb_image[1,*,*] = image
rgb_iamge[2,*,*] = image
tv, image, /true

This has the effect of changing every pixel where the mask is
active from a greyscale to cyanscale value. If you are running in 8
bit colour you'll have to use COLOR_QUAN to construct a custom colour
table before using tv. Zapping the a different channel shades the
mask with the appropriate complementary colour.

A final tip: if, like me, you often end up creating masks which
cannot easily be created with a simple global selection criteria, it
is often easiest to export the image as a TIFF file, use Photoshop's
excellent selection tools to create a mask, and then load it back into
IDL.

Struan

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[Message index]

		Label_region and Erosion By: lbryanNOSPAM on Tue, 03 November 1998 00:00
		Re: Label_region and Erosion By: Struan Gray on Fri, 06 November 1998 00:00
		Re: Label_region and Erosion By: David Foster on Thu, 05 November 1998 00:00
		Re: Label_region and Erosion By: Alex Schuster on Thu, 05 November 1998 00:00
		Re: Label_region and Erosion By: Struan Gray on Wed, 04 November 1998 00:00
		Re: Label_region and Erosion By: lbryanNOSPAM on Wed, 04 November 1998 00:00
		Re: Label_region and Erosion By: Struan Gray on Wed, 04 November 1998 00:00

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