pyexiv2-developers team mailing list archive

[Olivier Tilloy <olivier@xxxxxxxxxx>]

On 2011-12-31, Jason Bishop <jason.bishop@xxxxxxxxx> wrote:
> Hello all, just joined (thanks Olivier) and wanted to share a little bit
> of code with you in case you thought it useful.  I got a canon 7d little
> while ago and noticed that the builtin screen indicates with red boxes
> which focus points were used.  I thought that was interesting so I went
> trudging through the exif info to see if I could generate images showing
> the focus points as well.  this is what i ended up with.  grey boxes
> showing all focus points. white for subset which were active when the
> shot was composed, and red for the ones that were used to take the shot.
>  please excuse the code duplication, i haven't cleaned up the code yet
> to deal with dcraw rotating the image for me.  You can just ignore the
> clauses for rotatepic==true.

Very interesting, thanks for sharing Jason!

Could you maybe post somewhere an original picture that embeds such
information? I’m curious to see the visual result, but I don’t own a
Canon camera.

Also, do you know whether those magic values you use to extract the data
are standard across all Canon cameras, or if they vary from one model to
the other? Did you base your work on some sort of specification, or did
you have to reverse-engineer the data?

> I was thinking that perhaps these values (focuspointwidth,
> focuspointheight, focuspointxpos, focuspointypos, activeafpoints,
> afpoints) could be exposed more directly.  interested in your thoughts.

It would make sense, especially if the format is common across all Canon
cameras. I’m thinking that it may be a good candidate for an API such as
the one requested in http://pad.lv/724185

Cheers,

Olivier