| Re: Colour maps overlaid on grey-scale (medical) images [message #14610 is a reply to message #14597] |
Thu, 11 March 1999 00:00  |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Jason Brookes (jason.brookes@rmsb.u-bordeaux2.fr) writes:
> I would like to know how to display colour overlays on medical images.
> For example, an overlay of bloodflow rate superimposed (in hot body
> colour scale) on grey-scale images of the brain. At the moment, I am not
> able to do this without obliterating the information in the original
> image. Is it possible to overlay a colour map onto a grey-scale image
> without obliterating information in the grey-scale image ? ie: by making
> the colour overlay "transparent" to some degree ?
There are probably more sophisticated ways to do this
(and I would like to hear about them), but here is a
quick and dirty method that has always worked quite
well for me.
The idea is to "half-tone" your image so that each
adjacent pixel is from the other image. By creating
two color tables and scaling the original images
appropriately into them, you can get a resulting image
that looks pretty darn close to what you want.
Here is a little example program using the elevation.dat
and ctscan.dat data sets in the IDL distribution. You
can download the LoadData program from my web page:
http://www.dfanning.com/programs/loaddata.pro
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
--
Pro Color_On_Gray, image_1, image_2
; Get the data sets if needed.
IF N_Params() EQ 0 THEN BEGIN
image_1 = Loaddata(7)
image_2 = Loaddata(5)
ENDIF
; Size the second image to fit the first.
s = Size(image_1, /Dimensions)
image_2 = Congrid(image_2, s[0], s[1], /Interp)
; Load the color tables. Gray-scale and Red Temperature
ncolors = !D.Table_Size
halfcolors = Byte(ncolors / 2)
LoadCT, 0, NColors=halfcolors
LoadCT, 3, NColors=halfcolors, Bottom=halfcolors
; Scale the data. First image uses gray-scale.
image_1 = Bytscl(image_1, Top=halfcolors-1)
image_2 = Bytscl(image_2, Top=halfcolors-1) + halfcolors
; Create a vector for pixelation.
x = Findgen(s[0]/2) * 2
; Pixelate the image.
image = BytArr(s[0], s[1])
image[x, *] = image_1[x, *]
image[x+1, *] = image_2[x+1, *]
image[*, x] = Shift(image[*, x], 1)
; Display image.
Window, XSize=s[0], YSize=s[1], /Free
TV, image
END
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