Maximum of the image size png Matlab

Hello,

I have a matrix T (1, 2761843)

I want save it as like an image .png. I used the following line:

Imwrite (T,['image' num2str(5) '.png']);

I just get the following error.

Error using pngwritec
PNG library failed: image size exceeds user limits in IHDR.

Error in writepng (line 280)
pngwritec(data, map, filename, colortype, bitdepth, ...

Error in imwrite (line 546)
        feval(fmt_s.write, data, map, filename, paramPairs{:});

No problem with JPEG 2000.

How I can find the maximum of image size .png (width and length) that we can create it with Matlab?

Thank you!

[Rik]

You could try if the savepng mex function on the FEX suits your needs. I'm very far from fluent in C++, but it doesn't look like there is a limit imposed beyond the png format itself.

If you want to use Matlab tools, you could consider reshaping your data, prepending the true size and padding with zeros.

Answer 1

[Rik]

Short answer: trial and error.

Long answer:

This should probably be somewhere in the doc. Only after the trial and error did I actually go look for it, but I didn't find it in the imwrite or imformats documentation.

The official png spec suggests the maximum size in either dimension would be anything that fits in 4 bytes, well above what you are trying to do. So officially there is nothing wrong with what you're trying.

However, a test on my copy of R2020a shows the maximum is 10^6. I find it curious that the limitation is a rounded decimal, and not a rounded hex (e.g. 0xFFFFF, 0xFFFFE, or 0x0FFFF).

The only other limit seems to be that 'Images must contain fewer than 2^32 - 1 bytes of data.' So your other dimension can 'only' be 4294 pixels. That required about 34GB of RAM and writes a png of just over 4GB.

clc
fn='foo.png';
%increasing either by 1 will return an error
dim1=floor(2^32/10^6);
dim2=10^6;
try
    if exist(fn,'file'),delete(fn);end
    IM=uint8(randi(255,4294,dim2));
    imwrite(IM,fn);
    fprintf('size %d written correctly\n',dim1*dim2)
catch ME
    fprintf('fail:%s\n',ME.message)
    if exist(fn,'file'),delete(fn);end
end

[K. Taieb]

Thank you!

I’m sorry, I don’t understand your explication “ Images must contain fewer than 2^32 - 1 bytes of data.”

Because if I can create an image.png with the same number of elements but with multi rows and multi columns.

T (1642, 1682), we can see 2761843 = 1642*1682+1.

[Rik]

That last limit only means you can't have an image with 2^32 pixels (grayscale) or 2^32/3 pixels (RGB), which is a reasonable limit, since 2^32/3 is 1431655765.33. So you shouldn't have any issues with that limit for any reasonable situation.

Answer 2

[Image Analyst]

If you want to save your 1-D vector as a 2-D image, I suggest you resize it first using reshape().