How to use IF with @(block_struct) function

fun2 = @(block_struct) ...
   if block_struct.data < 100
    std2(block_struct.data) * (block_struct.data));
   end

Doesnt work.

I actually want to manipulate individual elements of my block

blocks made of 8x8 values ranging from 0-255

[Geoff Hayes]

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 block_struct.data < 100
    std2(block_struct.data) * ones(size(block_struct.data));
   end

is an anonymous function? If so, then I don't think that the above is valid...

[Saud Alfalasi]

Hi Geoff

blockyImageR = blockproc(redChannel, blockSize, fun);
blockyImageG = blockproc(greenChannel, blockSize, fun);
blockyImageB = blockproc(blueChannel, blockSize, fun);
blockyImageR(1)
blockyImageG(1)
blockyImageB(1)
rgbImage2 = cat(3, blockyImageR, blockyImageG, blockyImageB);
imshow(rgbImage2)

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

Answer 1

[Athul Prakash]

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
    if(block_struct.location(2)==101)
        % skipping the 2nd block.
        out = block_struct.data;
    else
        % code for processing every other element
    end
end

Hope it helps!

[Saud Alfalasi]

Wow this is brilliant Thank you ever so much Saud

[Athul Prakash]

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 ;).

Cheers!

[Saud Alfalasi]

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

Saud