Increasing bit depth of an image from 4 bit to 8 bit

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Muhammad Hamid 2011-9-22

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https://ww2.mathworks.cn/matlabcentral/answers/16453-increasing-bit-depth-of-an-image-from-4-bit-to-8-bit

Hi I have an image of skull in gray format and i first decreased its bit depth from 8 bit to 4 bit,which was easy but now the problem is with recovering the original image from this transformed 4 bit image to 8 bit.....hope u got my point... waiting for the reply..

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Jan 2011-9-22

Please post how you converted it to 2 bits. As far as I can see, some color information is lost by this procedure. Then you cannot recover the original image.

Muhammad Hamid 2011-9-24

i have used "bitand" fuction for this reason

Image=bitand('originalimage',240)

now it is reduced to 4 bit

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回答（1 个）

Walter Roberson 2011-9-22

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https://ww2.mathworks.cn/matlabcentral/answers/16453-increasing-bit-depth-of-an-image-from-4-bit-to-8-bit#answer_22249

You cannot recover the full depth of an image if you reduced the image to below ceil(log2(N)) bits per pixel where N is the number of unique colors (or shades) in the image ( N = length(unique(IMG(:))) )

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Muhammad Hamid 2011-9-25

@Image Analyst: hahaha yes there were 2 images, sorry for my english..

Image Analyst 2011-9-25

Why would it work on one and not the other? Just divide by something (16) to get your image into the range 0-15 (a 4 bit range), and then multiply that by 16 to get it into the range 0-255 (an 8 bit range). Explain why you're unable to divide and multiply by 16 on *one* of the images. What error message do you get?

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