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Reason for size limit on imread [closed]

asked 2018-11-21 14:22:57 -0500

scottt gravatar image

updated 2018-12-03 17:23:12 -0500

I have successfully written images with sizes of about 60000x30000 (1,800,000,000 pixels), but when reading the image with imread, I get an assertion from these defined limits in opencv/modules/imgcodecs/src/loadsave.cpp:

#define CV_IO_MAX_IMAGE_WIDTH (1<<20)
#define CV_IO_MAX_IMAGE_HEIGHT (1<<20)
#define CV_IO_MAX_IMAGE_PIXELS (1<<30) // 1 Gigapixel

Are there specific requirements being met by these or are these limits just arbitrarily defined? In width and height for example, 1<<20 matches dimensions of 1,000,000, where 1<<16 = 65536 seems to make more sense. This is what leads me to believe they are arbitrarily defined. To be able to handle images up to a size of 65536x65536, CV_IO_MAX_IMAGE_PIXELS should be 2^32.

It doesn't make sense to be able to write an image out of a certain size but be unable to read it.

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Closed for the following reason the question is answered, right answer was accepted by LBerger
close date 2018-12-09 11:01:56.062478

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answered 2018-12-04 02:27:59 -0500

LBerger gravatar image

updated 2018-12-09 11:01:37 -0500

May be it's a bug and you can post an issue I tried this :

    RNG r;
    Mat m(60000, 40000, CV_8UC3);
    r.fill(m, RNG::UNIFORM, 0, 255);
    imwrite("test.png", m);
    Mat p = imread("test.png", IMREAD_UNCHANGED),d;
    cout << p.rows << " " << p.cols;
    absdiff(m, p, d);
    Scalar v = mean(d);
    cout << " mean=" << v << "\n";

and an exception is thrown (opencv 4.0.0 windows 10 visual 2017 win64) Now I changed in source code

#define CV_IO_MAX_IMAGE_PIXELS (1<<30) // 1 Gigapixel


#define CV_IO_MAX_IMAGE_PIXELS (1ull<<32ull) // 1 Gigapixel

and no exception is thrown (after opencv rebuild)

PR and now in imread doc :

By default number of pixels must be less than 2^30. Limit can be set using system variable OPENCV_IO_MAX_IMAGE_PIXELS

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Downvote is free but sometime world is not as you think.

LBerger gravatar imageLBerger ( 2018-12-04 04:23:33 -0500 )edit

There is a comment: // TODO Add runtime configuration

It is better to add support for reading these values from the environment (using utils::getConfigurationParameterSizeT). PR is welcome!

mshabunin gravatar imagemshabunin ( 2018-12-04 05:01:39 -0500 )edit

@Akhil Patel do you have an explanation to this?

sturkmen gravatar imagesturkmen ( 2018-12-07 16:14:12 -0500 )edit

+1 but i am afraid it is hard to reach more hits than the answer above :)

sturkmen gravatar imagesturkmen ( 2018-12-09 12:40:43 -0500 )edit

It does not matter. +6 it is artificial :

LBerger gravatar imageLBerger ( 2018-12-09 13:30:02 -0500 )edit

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Asked: 2018-11-21 14:22:57 -0500

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Last updated: Dec 09 '18