[PD] pix_dump and average?

[Thomas Ouellet Fredericks]

You can use pix_blob.

[pix_video] //Or whatever
|
[pix_blob 1] //The size outlet will give the amount of red
|
[pix_blob 2] //The size outlet will give the amount of green
|
[pix_blob 3] //The size outlet will give the amount of blue

As an added bonus, you get centers of gravity.

Tom


On 4/10/06, Tina Shah <surreal8 at hotmail.com> wrote:
> thanks IOhannes!  yea, the average is just wrong with the current patch and
> you're right, i do not want to include the alpha values.  i am using gem
> .90, and pix_mean_color will be very helpful in the future since that's
> exactly what i want to do!  i will look at frank's list-average abstraction
> and see if it helps.  i tried to use pix_resize and set it to 1 1, but it
> didn't work, and it also didn't really work regularly... btw, i thought it
> was weird that i was getting two floats, glad i could help in finding a bug
> :-).
>
> tina
>
> ----Original Message Follows----
>
> hi
>
> Tina Shah wrote:
>  > Hi List, I'm trying to get the average color data from an image.  I'm
>  > using pix_dump and then trying to use 'average' to get the average of
>  > the dump, but the numbers are not matching.  i tested just a 1 pixel
>  > image, got 4 values - 0.341176 0.360784 0.345098 1 - but the average is
>  > wrong - average: 0.35098.
>
> hmm: what exactly is wrong? is "0.35098" the output of the [average]
> object? or is it what you expect (because you know the image)?
>
> i cannot reproduce the former: on my machine, [average 4] outputs
> 0.511765 when i send it [0.341176, 0.360784, 0.345098, 1(
> i cannot reproduce the latter (since i don't have the image)
>
>  > anybody know what i'm doing wrong or know of
>
> well:
> [pix_dump] outputs a list(!) of values (r,g,b,a,r,g,b,a,...) AND
> you cannot send a list to [average], it needs single numbers. so you
> need to convert the list into a stream of numbers.
> using a numberbox ([ \) does NOT convert a list into a stream of
> numbers, it will just take the first number of that list and pass it on [1].
>
> [average] is a moving average filter, and while you can use it to
> calculate the total average of a list (with some tricks!), i would not
> naturally use it.
>
> the output of [pix_dump] also holds the alpha-value (the "1"), which you
> most likely will not want to include in your averaging.
>
>  > an easier way?  I'm on windows (pd .39-2) and just using gem...  BTW,
>
> what is "just using gem"? version?
> in gem-0.91 (still not released) there is [pix_mean_color] which
> calculates the average color of an image. (separate values for r, g, b
> and a)
>
> i don't know exactly what you want to get: separate values for r,g,b,a
> or 1 "grey" value?
> in the former case you will have to sort the output of [pix_dump] to
> give you separate lists (or streams of floats) for the 4 channels.
> since 0.39, you can do that with native pd objects (see frank's
> list-abstractions, which most likely also has a [list-average] which
> will output the total average of a list)
>
>  > does pix_resize work?
>
> i thought so.
> however, in older versions of gem you could not set the dimensions: it
> would just resize the image to the next power-of-2 size. (see the
> help-patch of the object whether in your version it is already able to
> resize to an arbitrary size).
> of course, if [pix_resize] does work for you, you could just use it to
> resize the image to 1x1 and then do a dump.
>
>  > thanks!
>
> i hope i gave you some clues....
>
> mfg.asdr.
> IOhannes
>
>
> [1]: hey! you have discovered a bug!! sending a list of floats to a
> numberbox will output 2 values (the 2nd and the 1st)!!! this should be
> fixed in 0.40
>
>
>
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