[PD] pix_buf & pix_snap

[zmoelnig at iem.at]

Zitiere lists at martinmalm.com:

> Hi !
> 
> Is there some way to get a 'snapshot' from a videosource (pix_video or
> pix_film) without using pix_snap ? This does't seem to work with
> pix_buf
> since its "only effective if it is storing a static image".

the hint, that [pix_buf] is only effective with static images is a bit 
confusing.
it means, that copying a whole image each frame from one position in memory to 
another is "ineffective". (therefore pix-operations are done in-place if 
possible)
[pix_snap] does transfer the pixel-data from grafix-card to main-memory, which 
is even less effective - a) because you have to do the copying as in [pix_buf], 
+ b) (more important) because openGL is a client-server machine, that has fast 
transfers client2server (eg. setting the state of the rendering engine) but 
quite slow transfers server2client (eg. obtaining the rendering-buffer)
thus [pix_snap] is certainly not what you want.


[pix_buf] might be alright, but ít buffers all the new images that arrive, so 
you won't be able to get a still-image of a video. (as far as i remember)

the solution might be [pix_buffer]+[pix_buffer_read]+[pix_buffer_write] (ok, 
looks a bit clumsy -- shooting with canons at sparrows, as we say in austria)
basically it works like [table]+[tabread]+[tabwrite].
it is only available with the CVS-version and there should be a basic help-file 
somewhere (either in the examples/04.pix (i guess so) or in the reference-
patches)

since processing is done inline, you will probably have to use an additional 
[pix_buf], to be able to process the same image differently...

mfg.a.srd
IOhannes