usb-imagewriter does not support compressed images

[Matt Sealey]

Binary package hint: usb-imagewriter

USB ImageWriter should support compressed images. It is a good idea because it reduces bandwdith and storage space on the servers, and allows less disk usage on the host system to write the image out (a 650MB .img file for ARM Netbook could be made much smaller)

Since it just chains commands like "dd" through the Python script piping compressed data to dd would be easily implemented. Certain compression utilities (xz) will also report the uncompressed size such that progress can be reported properly.

Should also support dcfldd if installed (or other dd clones or improvements) such that progress could be properly reported by catching and parsing the output of stderr from the "dd" utility used. In lieu of that why can't imagewriter.py send the HUP signal to dd and catch progress every second or so, so that the progress bar can be implemented properly?