Add example to dictionary (was Re: Help on export snapshot)

[Richard Gaskin]

Mark Schonewille wrote:

> on mouseUp
>     put "~/desktop/test.png" into myFile
>     if there is a file myFile then delete file myFile
>     set the filetype to "????PNGf"
>     export snapshot from rect (the rect of this stack) to file myFile
> as PNG
> end mouseUp

The "from rect" option will grab a portion of the rendered image from 
the display device buffer, which will include portions of any other 
window which may overlap.

For a true WYSIWYG grab that may be exactly what's needed, but if you 
want to grab only a specific window, or even an object within that 
window, without anything else in the image, you can use the "export from 
<object>" form introduced in v2.7.

Oddly enough, stacks cannot be used as the referenced object, so this 
won't work:

   export snapshot from this stack to file myFile

But cards can, so this will work:

   export snapshot from this cd of this stack to file myFile

With v2.7 Mark Waddingham did a massive overhaul to the way objects are 
rendered in order to better accommodate modern OS buffering schemes 
along with antialiasing and more, and thankfully implemented it in a way 
that exposes those buffers to us with this new option for "export snapshot".

The engine still supports the grab from the general display buffer by 
specifying a rect, which will then grab it from the OSes master display 
which includes all windows.

But if you need to render just a specific object, you can trigger Rev's 
internal buffering routines to create a buffer into which it will render 
that for you and hand you the resulting image data, using the "...from 
<object>" option.

Which is better will of course depend on what you want to do.  But it 
can be handy for Paul to know both forms to pick the one that works best 
for what's needed.  His original attempt at using "this window" was very 
close; just changing that to "this cd of this stack" should do what he 
was looking for.

--
  Richard Gaskin
  Fourth World
  Revolution training and consulting: http://www.fourthworld.com
  Webzine for Rev developers: http://www.revjournal.com