| Re: how to make a mask from a picture and how to put... [message #38404] |
Thu, 04 March 2004 10:56  |
Thomas Nehls
Messages: 24
Registered: March 2004
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Junior Member |
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David Fanning wrote:
> Thomas Nehls writes:
>
>
>> thank you that is interesting, but:
>>
>> I especially want to avoid drawing by hand! I already have my black and
>> white image bw (1,400,400) which results by some calclations from the
>> original image "org"(3,400,400).
>> Now I want to multiply these two images in that way, that everywhere
>> where my "bw" is black (or white, whatever) should be black in the
>> resulting image "res". the following loop did not work...
>> for x=400, Y=400
>> for X = 1:400
>> for Y =1:400
>> res(Z=0:3,X,Y) = bw(X,Y) * org(Z=0:3,X,Y)
>> end
>> end
>> end
>> Do you understand what I want to do?
>
>
> Yes, but I was hoping you would be able to read between
> the lines a bit. (I don't know why I thought this. I
> haven't had a bit of luck this week! But there you go,
> an eternal optimist!)
>
> OK, I would REFORM your B&W image into a 2D array, not
> a 3D. You will just get confused with that extra
> 1 dimension hanging around. (Or, at least, I do.)
>
> image = Reform(bw)
>
> I'm going to assume black image pixels are 0, everything
> else is something other than 0.
>
> mask = image GT 0
>
> Mask now contains a 1 where you want the "light" to shine
> through and 0 where you want to block it. If your situation
> is the other way around, subtract 1 from mask.
>
> Now you have to apply the mask to the three image
> planes. Let's rearrange your pixel interleaved image into
> a band interleaved so we don't have that pesky 1 dimension
> to deal with:
>
> maskedImage = Transpose(res, [1,0,2])
>
> Now apply the mask to each color plane:
>
> FOR j=0,2 DO maskedImage[0,0,j] = maskedImage[0,0,j]*mask
>
> If you *have* to have a pixel-interleaved image:
>
> maskedImage = Transpose(maskedImage, [2,0,1])
> TV, maskedImage, True=1
>
> Cheers,
>
> David
>
Hey David,
I read between the lines but I did not know how to merge the three
masked color layers... now, I know...
I wish you a big bit of luck until this week closes! Less stupid
students like me for instance...;-) Something comparable to the luck I -
absolute IDL beginner - had, when found this newsgroup...
Thank you very much for your hints,
Tom
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