AW: AW: How to test if an image is empty?

[Tiemo Hollmann TB]

Great explanation, I wasn't aware of that.
thank you Ken
Tiemo

> -----Ursprüngliche Nachricht-----
> Von: use-livecode-bounces at lists.runrev.com [mailto:use-livecode-
> bounces at lists.runrev.com] Im Auftrag von Ken Ray
> Gesendet: Montag, 11. Juli 2011 15:29
> An: How to use LiveCode
> Betreff: Re: AW: How to test if an image is empty?
> 
> > Thanks Mark and Scott,
> > "the text" ... hmm, not the first to think about with an image :)
> 
> If it helps, Tiemo, you can use this:
> 
>   put "" into image 1
> 
> and
> 
>   if image 1 is empty then...
> 
> The "text" property is implied in the same was as for fields ("put field 1
> into.." vs. "put the text of field 1 into...").
> 
> Here's a good way to think about images: there's a distinction between the
> actual image binary data and what is used to show the user what the image
> currently looks like (including scaling, rotation, rendering in various
> quality levels, the "paintCompression", etc.). The binary data is the
image's
> *contents* (the 'text' of the image in this case), and what is shown to
the
> user is the 'imageData'+'maskData'+'alphaData' (which I'll just call
"image
> data"). If you empty out the image data, the binary data still exists -
all
> you've done is to say (in effect) "don't show this image to the user", or
more
> accurately: "show blank to the user".
> 
> You can have binary data without image data but not the other way around;
once
> you set the image data of an image, the binary data is *created* to
support
> the image data you set. This can be very useful in keeping a scaled
version of
> an image in a stack without holding on to all the extra "weight" of the
> original image.
> 
> So for example, if you imported a 100K image that was 1000 x 1000 pixels
and
> then scaled it down to 100 x 100 (and set the lockLoc to true so it
doesn't
> "pop" back to its original size), the user would see 100 x 100 pixels of
image
> data, but the image would be storing 1000 x 1000 pixels of binary data.
> However, if you created a new blank 100 x 100 image an then executed:
> 
>    set the imageData of img 2 to the imageData of img 1
>    set the alphaData of img 2 to the alphaData of img 1
>    set the maskData of img 2 to the maskData of img 1
> 
> the binary data for img 2 would only be what is necessary to support what
the
> user sees (100 x 100 pixels). It would look exactly like image 1, but
would be
> only 1% of the original number of pixels and would only take up 1K instead
of
> 100K. You could then delete image 1 and you'd have exactly what you
started
> with but storing a bunch less space.
> 
> This is great for working with thumbnails of full-resolution images; of
course
> if you *need* to keep the full-res image around because the image might
scale
> *up* from 100x100 to 1000x1000 (or any size in between) then you want to
work
> with the full-res image and not make a "cheap copy", but you get the idea.
> 
> I have a very old (but still mostly accurate) primer on imageData,
alphaData,
> and maskData here:
> 
> http://www.sonsothunder.com/devres/revolution/tips/imag003.htm
> 
> Hope this helps,
> 
> Ken Ray
> Sons of Thunder Software, Inc.
> Email: kray at sonsothunder.com
> Web Site: http://www.sonsothunder.com/
> 
> 
> 
> > Thanks for your quick response
> > Tiemo
> >
> >> -----Ursprüngliche Nachricht-----
> >> Von: use-livecode-bounces at lists.runrev.com [mailto:use-livecode-
> >> bounces at lists.runrev.com] Im Auftrag von Scott Rossi
> >> Gesendet: Montag, 11. Juli 2011 11:48
> >> An: LiveCode Mail List
> >> Betreff: Re: How to test if an image is empty?
> >>
> >> Recently, Tiemo Hollmann TB wrote:
> >>
> >>> when I put empty into img "foo" the imagedata of img "foo" is still
not
> >>> empty, there are still any binary data in the image.
> >>>
> >>> I can't test if the imagedata of img "foo" is empty" nor can I test if
> > the
> >>> img "foo" is empty. How can I test if I have put empty into an image?
> > Can I
> >>> test it binary?
> >>
> >> To "truly" empty an image, I set the text property of the image to
empty,
> >> and also check that property to make sure it's empty.
> >>
> >>  return (the text of img 1 is empty)
> >>
> >> Regards,
> >>
> >> Scott Rossi
> >> Creative Director
> >> Tactile Media, UX Design
> >>
> >>
> >>
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