Brace indexing into the result of a function call is not supported

Hello I was attempting to run a code I had. The code is below:

%focus stacking function using Laplacian pyramid 

function resultImage = focusStack(imageStack)
    numImages = numel(imageStack);

    %Convert images ti double for processing 
    for i = 1:numImages
        imageStack{i} = im2double(imageStack{i});
    end

    %Initialize Laplacian pyrimid for each image
    laplacianPyramid = cell(1 , numImages);
    for i = 1:numImages
        laplacianPyramid{i} = laplacianPyramid(imageStack{i});
    end

    %combine Laplacian pyramid to create the final result 
    blendedPyramid = blendLaplacianPyramids(laplacianPyramid);

    %Reconstruct the final focus-stacked Image
    resultImage = reconstructFromPyramid(blendPyramid);
end

% Laplacian pyramid generation for an image

function pyramid = laplacianPyramid(image)
    levels = 6; %Number of pyramid levels (adjust as needed)
      pyramid = cell(1, levels);
      pyramid{1} = image;
    
      for i = 2:levels 
        smoothed = imgaussfilt(pyramid{i-1}, 2); %Apply Gausian smoothing 
        difference = pyramid{i-1} -smoothed; %Compute difference 
        pyramid{i} = difference;
      end
    end

    %blend the laplacian pyramid to create the final result 
function blendedPyramid = blendLaplacianPyramids(pyramids)
    numLevels = numel(pyramid{1});
    blendedPyramid = cell(1, numLevels);
    
    for level = 1:numLevels
        blendedLevel = zeros(size(pyramids{1}{level}));
    
        for level = 1:numel(pyramids)
            blendedLevel = blendedLevel + pyramid{1}{level};
        end
    
        blendedPyramid{level} = blendedLevel;
    end
    end
%Reconstruct image from blended Laplacian 
function resultImage = recontructFromPyramid(pyramid)
    numLevels = numel(pyramid);
    resultImage = pyramid{numLevels};

    for level = numLevel-1:-1:1
        expanded = imresize(resultImage, size(pyramid{level}), 'bilinear');
        resultImage = expanded + pyramid{level};
    end 
end 

I ran the code above and got the following error:

Error: File: focusStack.m Line:
40 Column: 23
Brace indexing into the result
of a function call is not
supported. Assign the result of
'pyramid' to a variable first,
then brace index into it.

Do you know of a way to resolve this issue.

Answer 1

[DGM]

Hm. I'm going to guess on this one.

function blendedPyramid = blendLaplacianPyramids(pyramids) % the variable is 'pyramids'
numLevels = numel(pyramid{1}); % but it's singular here
blendedPyramid = cell(1, numLevels);

for level = 1:numLevels
    blendedLevel = zeros(size(pyramids{1}{level})); % plural here
    
    for level = 1:numel(pyramids) % plural here
        blendedLevel = blendedLevel + pyramid{1}{level}; % singular here

My guess is that 'pyramid' is supposed to be 'pyramids'. Since 'pyramid' isn't a defined variable, it's instead resolving as a function somewhere on your path and causing the admittedly confusing error.

[Bryce]

Thank you that helped resolve the issue. I did however run into another issue if you are able to help

Array indices must be positive integers or logical values.

Error in focusStack (line 14)

laplacianPyramid{i} = laplacianPyramid(imageStack{i});

[DGM]

Ah. You're creating a variable called laplacianPyramid, but you're also trying to use a function by the same name. Once you create the variable, the RHS of that line is an indexing expression where the values in imageStack{i} are not integer-valued, hence the error. Rename one of the two so that they don't cause conflict.

[Bryce]

Thanks again!

[DGM]

no problem