livfoss at mac.com
Sun Sep 20 14:02:30 EDT 2009
Thanks to all who replied. I think my immediate problem was trying to
get stuff from a rectangle that extended beyond the actual rendered
area, as Richard mentions: this causes an 'Execution Error' with no
further detail, so it's hard to know what has gone wrong - but finger
However Richard your other point:
> The rect option can be useful at times, but since v2.7 we've had a
> easier and more robust method of exporting images of objects by
> specifying the object itself rather than a rect:
> import snapshot from img "MyImage"
> The object needn't be an image; it can be anything other than a stack
> (referencing the card will work for those), even groups.
> The big difference is how the image is generated:
> Using the rect option cips a portion of the display buffer, so if
> image is out of bounds there won't be anything to get.
> But using an object reference causes the engine to render the object
> into a private buffer for you, much like it would do when rendering
> image on a card, and then hands that buffer back to you in the
> In my experience using object references is reliable under a much
> range of circumstances than using rects, even with objects on cards
> aren't open.
> This extension to the snapshot syntax was a by-product of the massive
> rendering overhaul Mark Waddingham did for v2.7, and one that's done
> wonders here for making screenshots very easily.
Is not so easy to follow if you're trying to build up a composite
image: say for the sake of argument one has a picture (an image)
occupying some part of a card, and one imposes on top of it another
image, with the intention of snapshotting the combined image so as to
create a new picture that can be exported: it might be a jpg of a
membership card with the member's picture imposed on it, or something
like that. Then if I import a snapshot of my background image (the
card design), won't my foreground image (the member's picture) be
ignored? That's how I read the docs - so what I did in the end was to
use a rect based on the background image, something like:
import snapshot from rect (the rect of of img "MembershipCard")
This worked, but it appeared to me that I had to have a window (card,
stack) as big as the whole background image if nothing is to be
clipped, which was inconvenient.
Anyway I have cracked it, but I don't think the docs tell you all the
ins and outs - and IMHO there aren't enough examples.
More information about the Use-livecode