Image formats JPG, PNG and GIF without animation are supported. Transparence isn't supported. IPTC and EXIF datas are retrieved from JPG pictures.
If you are getting these error messages when you upload some pictures, that's because you have reached the memory limit allowed by your server.
More your pictures are large (pixel dimensions) and more your memory are used.
To avoid the problem, resize your pictures before upload.
If you can edit de configuration files of your server, you can change de value of memory_limit in php.ini.