how can i load into MATLAB specific pixels of a .tiff file?

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Orel Levy
Orel Levy 2021-1-14
评论： Walter Roberson 2021-1-24
I need to load into MATLAB a lot of .tiff files (a few thousands), and to speed the process I wanted to read only the interesting pixels (or index) from any file.
is there a way to do it without loading the full files?

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Pratheek Punchathody
Refer to the documentation on Read Specified Region of TIFF Image which alows you to read the specified region of the TIFF image. If that does not suit your needs then possibly reading in portions of it and cropping as you go can be a better option.
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Walter Roberson
Walter Roberson 2021-1-24
https://github.com/striges/mexgdal is an interface to gdal which supports sparse tiff files, and can do so automatically (tiles with content 0 are not written if the flag is set)
imwrite() would not be suitable for writing selected tiles, but the Tiff() matlab class can do so. Your reading code would need to check which tiles existed. I think gdal's developed interface would be easier to deal with.
Walter Roberson
Walter Roberson 2021-1-24
It even might happen to be the case that the new georaster function can read such a file; that would have to be tested
Note that the geotiff and gdal functions return full arrays and that Simulink has no sparse signal support. What you would gain would be in reduced file operations but full memory arrays would have to be used. But you could lose a lot of efficiency back if you were doing the tiff tile handling at the MATLAB level to reconstruct the entire matrix, which is one of the reasons I would suggest farming out to gdal for its built-in handling.

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