Homebrew PCBs

Andrew wrote:
>>Roger wrote:
>>
>>I am very interested in your approach, code
>>etc etc, although I will probably use a PIC
>>for the raster handling since I already have
>>a PIC controlling the 3 axes and the spark
>>control. I never thought of the TIFF format.
>>Please post anything you develop, all will
>>be gratefully received. 
> 
> 
> Roger - I missed this part in the TIFF FAQ
> 
> <Quote from a TIFF faq>
> 
> Question 7. Can I not stream TIFF? Why does my
> library need seeking forward and backward in
> my TIFF file?
> 
> TIFF is not a streamable format. It is its
> very nature that all data blocks can be
> written in any order that is convenient for
> the particular application and/or TIFF
> encoding library.
> 
> </Quote>
> 
> The first TIFFs I looked at where suitable
> for streaming.  They had the information
> header in front of the actual picture data.
> 
> However the main app I use, and I guess a lot
> of people do, is irfanview.  It saves TIFF
> with the header at the end of the file.
> Many other apps probably do the same.
> 
> This just can't work for the plotter (or I
> guess for your EDM).  This is because the
> ATMEL (or PIC) does not have enough memory
> to hold the whole file.  It has to burn each
> line as it receives it and then discard that
> data to buffer the next line.
> 
> Problem here is that you don't get to find
> out things like how wide and how long the
> file is in pixels until you get to the end
> of it.

Just get the PC to re-order the file before sending it.

Decent software decomposes the data (in whatever image
format) to specialized control instructions for the machine
anyway.