Ok - maybe it's just me being a bit dense (could well be, had no coffee yet!), interesting to compare the image sizes of similar Rockchip Bench Tool images, one previously supplied by Paul in the pinned thread and this one supplied by hal2710 : -
size:1,179,853,112 bytes - hudl.20130923.020558.stock.img
size: 635,541,816 bytes - TabbieDroid_Hudl.img
After replacing/modding the stock recovery with CWM and removing bloat/Tesco apps etc, have we really gained a reduction in image size of nearly 520MB
It's a given that the bloat/Tesco apps probably account for 75MB (according to the sizes given for disabled apps on a running hudl) so the simple question is what sort of stuff accounted for the other approx 445MB?
Or is that where I've misunderstood... ... very happy for someone to shout out the errors of my thoughts
I've recently taken a quick look at this image. Here's what is going on.
The individual image files (kernel.img, boot.img, recovery.img, system.img etc) have been pulled from a hudl based on the information in parameters, I would think with rkflashtool. rkflashtool just follows orders so it pulls data from a given offset and of a given length and writes it to a file.
If you inspect the individual images mentioned above with a hex editor you will find some interesting things.
kernel.img this is a file where every byte is 0x0, totally blank 8.4MB of nothing. Presumably no stand alone kernel has ever been flashed on the hudl as received from tescos. More on this in a bit.
boot.img, recovery.img the latter half of these img files seems to made of 0xff so about half of each of these files ins just padding.
system.img this is 1 GB in size as specified in parameters. Again about half of this is empty space.
If you make up a custom ROM fro these images and discard all the padding then it will be much smaller as you observe.
I mentioned the stand alone kernel is blank, on a custom ROM you really want a working standalone kernel and a boot without embedded kernel. If you have this arrangement it's easy to swap out the stock kernel for alternate kernels (change of branding, overclocking etc). Unpacking boot and extracting kernel gives a kernel of 8.7MB. Once signed using rkcrc -k this will do the job fine. However the hudle kernel is bigger than the space allocated to it in parameter 0x4000, so you will need to update the size allocated to kernel to 0x6000 and then adjust the offsets of the following images.
Hope this of some use to you.