atom feed14 messages in at.iem.pd-listRe: [PD] GEM - alpha blending of imag...
FromSent OnAttachments
Item StateFeb 16, 2007 9:44 am.pd, .pd
Item StateFeb 16, 2007 10:29 am.pd
Oli44Feb 16, 2007 10:47 am 
chris clepperFeb 16, 2007 10:51 am 
cyrille henryFeb 16, 2007 11:12 am 
Item StateFeb 16, 2007 11:18 am.pd
Kyle KlipowiczFeb 16, 2007 11:22 am 
Item StateFeb 16, 2007 11:32 am 
Item StateFeb 16, 2007 11:49 am 
cyrille henryFeb 16, 2007 12:03 pm 
Roman HaefeliFeb 16, 2007 12:52 pm 
Item StateFeb 16, 2007 1:10 pm 
Roman HaefeliFeb 16, 2007 1:33 pm 
chris clepperFeb 16, 2007 1:38 pm 
Subject:Re: [PD] GEM - alpha blending of images over movies
From:Item State (item@yahoo.de)
Date:Feb 16, 2007 11:18:45 am
List:at.iem.pd-list
Attachments:
gemTest2F.pd - 7k

hi,

i'm on osx 10.4 intel with pd-0.39.2-extended-test7, gem says "GEM: ver: 0.91-cvs", "GEM: compiled: Jan 5 2007".

the wrong colours appear equally when using TIFF images. to which object should i send the colorspace message? if i put it into [pix_movie], i get:

"error: pix_movieDarwin: no method for 'colorspace'".

interestingly, if i remove all the [pix_texture] objects and use [pix_draw] instead, the colours are displayed correctly (only i'm worried since the help says pix_draw is very slow compared to pix_texture, and i need to draw lots of CPU for audio later on).

also, if i use [pix_draw] instead of [pix_texture], i am able to use [pix_mix] (doesn't work with pix_texture?), so i can crossfade to a totally transparent picture, which does almost the fade-in/out i want. however, the pixel mixing is strange: the image becomes white before it's faded out. that is, pix_mix seems to to be assuming something like "alpha premultiplied", like stolidly multiplying each channel separately and not using alpha information for R/G/B multiplication:

http://sciss.de/test/Bild%203.png (you see the background of the text in the second screen from the left has gotten white instead of staying black ; this is the patch "gemTest2G.pd", using this transparent image : http://sciss.de/test/transp.png)

last not least, the images appear 180 degrees rotated when using pix_draw instead of pix_texture (see also Bild 3.png)

ciao, -sciss-

--- chris clepper <cgcl@gmail.com> wrote:

What OS and GEM version?

On OSX the pix_film/movie object defaults to YUV. Send a 'colorspace RGBA' message to the object before loading the clip if you need the alpha from the clip. pix_image uses RGBA by default. If you have problems with PNG the try uncompressed or TIFF.

Also, put the alpha object after the pix_objects.

On 2/16/07, Item State <item@yahoo.de> wrote:

hi,

i'm trying to port a former jitter patch to pd/gem

(http://lists.puredata.info/pipermail/pd-list/2006-11/043853.html).

i have problems getting overlayed images to display properly. i have four rectangles fed by pix_movie, then i need to fade in and out a rendered text image. i tried using pix_image -> pix_texture and [alpha 1]. the images are .png with transparent portions. i once got it to display correctly, but now if i open the patch, the videos all show up with wrong colours:

http://sciss.de/test/Bild%201.png (see attached patch gemTest2.pd)

once i remove the pix_image and pix_texture, save the patch and re-open it, the videos show up correctly again:

http://sciss.de/test/Bild%205.png (see attached patch gemTest2B.pd)

... also, i don't know how to fade in the text (the "action" string). is there an alpha-channel multiplier for pix_image? thanks for hints!

is it possible to stretch the video so that the rectangle stays the same, but only the top part of the video is shown (vertically zoomed without interpolation, so that you can see the pixels)?

ciao, -sciss-

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