imformat shows what can be read with imread():
>> imformats
EXT ISA INFO READ WRITE ALPHA DESCRIPTION
-----------------------------------------------------------------------------------------
bmp isbmp imbmpinfo readbmp writebmp 0 Windows Bitmap
cur iscur imcurinfo readcur 1 Windows Cursor resources
fts fits isfits imfitsinfo readfits 0 Flexible Image Transport System
gif isgif imgifinfo readgif writegif 0 Graphics Interchange Format
hdf ishdf imhdfinfo readhdf writehdf 0 Hierarchical Data Format
ico isico imicoinfo readico 1 Windows Icon resources
j2c j2k isjp2 imjp2info readjp2 writej2c 0 JPEG 2000 (raw codestream)
jp2 isjp2 imjp2info readjp2 writejp2 0 JPEG 2000 (Part 1)
jpf jpx isjp2 imjp2info readjp2 0 JPEG 2000 (Part 2)
jpg jpeg isjpg imjpginfo readjpg writejpg 0 Joint Photographic Experts Group
pbm ispbm impnminfo readpnm writepnm 0 Portable Bitmap
pcx ispcx impcxinfo readpcx writepcx 0 Windows Paintbrush
pgm ispgm impnminfo readpnm writepnm 0 Portable Graymap
png ispng impnginfo readpng writepng 1 Portable Network Graphics
pnm ispnm impnminfo readpnm writepnm 0 Portable Any Map
ppm isppm impnminfo readpnm writepnm 0 Portable Pixmap
ras isras imrasinfo readras writeras 1 Sun Raster
tif tiff istif imtifinfo readtif writetif 0 Tagged Image File Format
xwd isxwd imxwdinfo readxwd writexwd 0 X Window Dump
since lpeg is not in there, you're going to have to find a reader for it, or else export the images in a format which is listed above.
