How to use IF with @(block_struct) function

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fun2 = @(block_struct) ...
if < 100
std2( * (;
Doesnt work.
I actually want to manipulate individual elements of my block
blocks made of 8x8 values ranging from 0-255
Geoff Hayes
Geoff Hayes on 22 Nov 2020
Saud - can you show us what the block_struct looks like with respect to attributes/properties? Presumably it has a data field. It isn't clear to me why you are doing
fun2 = @(block_struct) ...
where block_struct is the input to some function. Or are you hoping that all of the code
fun2 = @(block_struct) ...
if < 100
std2( * ones(size(;
is an anonymous function? If so, then I don't think that the above is valid...
Saud Alfalasi
Saud Alfalasi on 22 Nov 2020
Hi Geoff
blockyImageR = blockproc(redChannel, blockSize, fun);
blockyImageG = blockproc(greenChannel, blockSize, fun);
blockyImageB = blockproc(blueChannel, blockSize, fun);
rgbImage2 = cat(3, blockyImageR, blockyImageG, blockyImageB);
I'm trying to create a method of LSB insertation based on a sequece to do with individual blocks.
Just as a test I'm trying to only change values of numbers in my block according to the values.
the data field is is part of the array with is a 9x9x1 block
I would also like to try and pinpoint the minddle value of my block (coordinates 2,2) and do a quoteince differnce betwen it and the surrounding values.
Ideally what I want to do is not only change values in blocks but also manage the sequence of movement from block to block - example follwing some kind of sequence which results in going from block1 > block 7 > block 27

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Accepted Answer

Athul Prakash
Athul Prakash on 24 Nov 2020
Hi Saud,
Since blockproc uses anonymous functions, you may save your multi-line function into a script, say myFunc.m and then pass @myFunc to your blockproc call.
You can find block_struct structure described in the following doc (under More About section): 'blockproc' Documentation.
You may work out a way to manage the sequence artificially using some of those fields. For example, using block_struct.location to skip processing the 2nd block:
function out = myFunc(block_struct) % size would be 100x100
% skipping the 2nd block.
out =;
% code for processing every other element
Hope it helps!
Athul Prakash
Athul Prakash on 24 Nov 2020
Glad to help. Have you considered accepting this answer? On this platform, 'Accepting' is considered the highest form of validation for any answer. In addition to expressing the Questioner's satisfaction/gratitude, Accepting also makes an answer more discoverable to the rest of the community browsing this platform.
Not to blow my own trumpet though ;).
Saud Alfalasi
Saud Alfalasi on 24 Nov 2020
Edited: Saud Alfalasi on 24 Nov 2020
Blow away, you gave great help. Answer has been accepted. May I ask if you're contactable in any way? I could do with some guidance

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