Matlab - Replace successive pixel with pixel from the left

Question

So, I've quantized a grayscale image with four quantized values. I'm trying to maintain the first pixel of each row of the quantized image and replace each successive pixel with the difference from the pixel to its left.

How would you code this in matlab and can someone explain this to me conceptually?

Also, my concern is that because the image is relatively uniform because of the quantization of the dynamic range, most of the image would appear black, no? It seems to me that only the transition areas and the edges will have some difference in quantized values.

Jonas Jonas · Accepted Answer · 2011-05-13T01:42:12

To create the difference to the pixel on the left, all you have to do is subtract the pixels in columns 1,2,3... from the columns 2,3,4...

%# create a random image with four values
randomImage = randi(4,[100,90]); %# use different numbers of rows and cols so we know which is which

%# catenate the first column of the image with the difference from the pixel to the left
%# for all pairs of columns in the image
differenceImage = [randomImage(:,1),randomImage(:,1:end-1)-randomImage(:,2:end)];

Yes, you'd expect quite a few uniform patches (which will be gray, since unless you plot the absolute value of the differences, there will be some that are negative).

Matlab - Replace successive pixel with pixel from the left

1 Answers