MATLAB: What is the difference between info(obj) and infoImpl(obj)

infoobject

I cannot find any information about info(obj), which I encountered in some code I am reading. It takes System object as an input and outputs a struct that contains information related to the object.

In the object definition, there is a line of code that goes

objinfo = info(obj);

but no local function definition. There is a local function

function s = infoImpl(obj)
    ...
end

but I can't see how these two relate to each other.

When I tried

help info

all I got was the function that prints information about MATLAB.

Thanks in advance for any help!

Best Answer

I have found the other 'info' function in the MATLAB documentation and I am posting it here in case anybody else has the same question in the future. Function Documentation

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MATLAB: How to update Tiff object in ImageAdapter class

I found something that fixes the issue, but I'm not 100% sure why it works. In any case, I have included the solution below. I will also be reporting this as a bug/documentation problem, as it is definitely not clear in the documentation of the TIFF class.

To fix this, I modified the changePage() function as follows:

function [] = changePage(obj, imageSize, tileSize)
    % get tags from last page, before we switch
    bitsPerSample = obj.TiffObject.getTag('BitsPerSample');
    sFormat = obj.TiffObject.getTag('SampleFormat');
    compression = obj.TiffObject.getTag('Compression');
    
    % increments to next directory, so next time we call blockproc
    % it will write to the next page
    obj.TiffObject.writeDirectory();
    
    % now write out new metadata for the new page
    obj.ImageSize  = [imageSize(1), imageSize(2), 1]; %length first
    obj.TileLength = tileSize(1);
    obj.TileWidth  = tileSize(2);
    obj.TiffObject.setTag('ImageLength',   obj.ImageSize(1));
    obj.TiffObject.setTag('ImageWidth',    obj.ImageSize(2));
    obj.TiffObject.setTag('TileLength',    obj.TileLength);
    obj.TiffObject.setTag('TileWidth',     obj.TileWidth);
    obj.TiffObject.setTag('Photometric',   Tiff.Photometric.MinIsBlack);
    obj.TiffObject.setTag('BitsPerSample', bitsPerSample);
    obj.TiffObject.setTag('SampleFormat',  sFormat);
    obj.TiffObject.setTag('SamplesPerPixel', 1);
    obj.TiffObject.setTag('PlanarConfiguration', Tiff.PlanarConfiguration.Chunky);
    obj.TiffObject.setTag('Compression',compression);
end

Essentially, I added the rest of the tags that came from the first page. As soon as call to setTag() for Photometric is called, the TiffObject magically contains the entries of previous setTag calls. At first I thought it was because Photometric makes another call to the Tiff class within it, so I rearranged the setTag calls like this:

    obj.TiffObject.setTag('Photometric',   Tiff.Photometric.MinIsBlack);
    obj.TiffObject.setTag('BitsPerSample', bitsPerSample);
    obj.TiffObject.setTag('SampleFormat',  sFormat);
    obj.TiffObject.setTag('SamplesPerPixel', 1);
    obj.TiffObject.setTag('PlanarConfiguration', Tiff.PlanarConfiguration.Chunky);
    obj.TiffObject.setTag('Compression',compression);
    obj.TiffObject.setTag('ImageLength',   obj.ImageSize(1));
    obj.TiffObject.setTag('ImageWidth',    obj.ImageSize(2));
    obj.TiffObject.setTag('TileLength',    obj.TileLength);
    obj.TiffObject.setTag('TileWidth',     obj.TileWidth);

Here, the TiffObject did not update until the setTag for ImageLength was called. What this tells me is that in order to update the TiffObject, a certain number of bytes must be written to the metadata. This is not at all clear in the documentation. I thought that rewriteDirectory() would work, but it does not update the TiffObject. It may actually write out to file like it says, but without the corresponding update to the TiffObject the code will crash the next time a tile is written, because it thinks the TileLength/TileWidth have not been set.

I am still open to answers on better ways to do my multi-resolution file writing, as this seems a bit haphazard, so feel free to add.

MATLAB: Changing variable (properties in class) by method

Your class is a value class as opposed to a handle class. See this documentation page for a description of the differences between the two. The "Modifying Value Objects in Functions" and "Modifying Handle Objects in Functions" sections on that documentation page describe what happens when you modify properties of an instance of each kind of class in a function or method. So you can either:

Define the methods in your value class to return the modified object, and call the methods with the object as both input and output.
Change your class to a handle class.

Best Answer

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MATLAB: How to update Tiff object in ImageAdapter class

MATLAB: Changing variable (properties in class) by method

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