tweak imread+imwrite to work with binary data instead of actual files ("just" skip file reading and writing)

dear all, has anybody tried tweaking imread and imwrite to read/write from/to (say uint8) data arrays rather than an actual (say png) file? basically "just" skip the binary file reading and writing in pngreadc (mexfile). background of my question is that i would like to use compressed images in hdf5 files. same applies to mp4 btw. any hint very much appreciated.

i created a very inefficient workaround by using imwrite to tempfile, then read this tempfile as uint8 (to get the data array) and finally delete tempfile.

PS: I contacted MW some time agao and they claimed it cant be done now, but noted feature request

[DGM]

Are you trying to get a copy of the raster data or the entire image (header, data and everything)? You've found out that most of the core support files are mex, so I don't really know how much work is worth avoiding the inelegance of a temp file.

If it makes you feel any better, you can write the temp files to /dev/shm or whatever the equivalent is in Windows. That would at least keep them off the disk.

[Roman Koetitz]

thanks for you comment DGM. i just care about the raw image array (2D gray valuies) no header. actually there will be thousands of images in one hdf5 file and hence data volume and storage and retieval time do matter. the images need to be retrieved as fast as possible to do a live update in an interactive user interface for browsing a kinetic. my tempfile is already in matlab's tempdir (working under W10)

[Roman Koetitz]

sorry didnt read your /dev/shm hint carefully enough first, yes a ramdisk might be an inexpensive compromise, havent used it under windows yet though

[AndresVar]

In the past I used the method someone else made to read frames from an MRAW recording. Basically just uses fopen, fseek and fread. I have not tried for your purpose but seems like you might be able to get some inspiration from these links:

Reader class for Photron .mraw-Files - File Exchange - MATLAB Central (mathworks.com) See the getFrame method

Photron MRAW File Reader - File Exchange - MATLAB Central (mathworks.com)

For what is worth eventually I switch to saving recordings as TIF files, because it was a pain to carry around huge single files (difficult to backup). Depends on how you use your data.