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How can I use wcodemat to re-scale an intensity/gray-scale image?

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Akshra
Akshra on 7 Dec 2016
Edited: Chaya N on 8 Dec 2016
I want to change my original intensity/gray-scale image into wcodemat for wavelet transform but problem is if i use
Y = wcodemat(X)
the image just turn into different shades of blue and this doesn't represent the original image(which is black and grey), I also cannot use
Y = wcodemat(X,NBCODES), because my image doesn't have map which is required for the NBCODES parameter.
How can I resolve this problem?

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Accepted Answer

Chaya N
Chaya N on 8 Dec 2016
Edited: Chaya N on 8 Dec 2016
You could get a map of your original grayscale image X using the contrast function
cmap = contrast(X)
This would give you a map of size CurrentGrayMap-by-3 which you could use when plotting your scaled image

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Akshra
Akshra on 8 Dec 2016
figure on the left is the original image and figure on the right is the re-scaled image using cmap.
Chaya N
Chaya N on 8 Dec 2016
Can you post the relevant code here? When calling wcodemat, you may need to call with the same NBCODES value as the length of the current colormap. If this length is small compared to the number of distinct gray levels you require for a smoother looking scaled image, then it appears 'thresholded' or having excess contrast as in your figure on the right. I would suggest you manually try to obtain as large a map length as possible. For an 8-bit image, this is usually 255-by-3. For example, you could obtain a 255 length colormap from your original image and call wcodemat with the same NBCODES=255.

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