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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="Author" content="Mark Danks">
<meta name="Author" content="IOhannes m zmölnig">
<title>Images</title>
</head>
<body>
<center>
<h2>
<u>Dealing with Images</u></h2></center>
Images are files which are loaded into GEM. The images can be manipulated,
applied to objects, and used in any number of different ways. In
this section, you will load in an image and display it on the screen.
This section will not apply the images to a <i>geo</i>; that occurs in
the next part of the manual.
<p>The pix objects are GEM objects which deal with <i>pix</i>els.
They do everything from loading in images to applying filters to the data.
The objects in this section of the manual only load in pix data from outside
sources. How you actually display the image is up to you. The
most common usages are with <i>[pix_draw]</i> and <i>[pix_texture]</i>.
<p><b>Warning</b>: <i>[pix_draw]</i> is almost always slower than <i>[pix_texture]</i>.
Because <i>[pix_draw]</i> is easier to use than <i>[pix_texture]</i>, it is
used in these examples. However, in any real usage or piece, <i>[pix_texture]</i>
should always be used instead. <i>[pix_draw]</i> is slow because PC
graphics accelerators do not provide hardware acceleration for that functionality.
<i>[pix_texture]</i> does have hardware acceleration and will be much faster.
<p><a href="#pix_image">[pix_image]</a> - load in an image
<br><a href="#pix_multiimage">[pix_multiimage]</a> - load in multiple images
<br><a href="#pix_movie">[pix_movie]</a> - load in a movie file
<br><a href="#pix_video">[pix_video]</a> - use a real time video source
<p><img SRC="tribar.gif" height=13 width=561>
<h3>
<a NAME="pix_image"></a>[pix_image]</h3>
<i>[pix_image]</i> is used to load in images. Images can be in a variety
of different formats, including TIFF, JPEG, and SGI formats. The
patch gem_pix/gemImage.pd is the simplest use of the <i>[pix_image]</i> object.
In this patch, the <i>[pix_image]</i> object loads in the file dancer.JPG.
<center>
<p><img SRC="pixImage.jpg" BORDER=1 height=180 width=151></center>
<p>As is the case with every GEM chain, this patch starts with the <i>[gemhead]</i>
object. The next object is <i>[pix_image]</i>, which actually loads
the image. <i>[pix_image]</i> makes the file dancer.JPG the current
pixel data, which will be used in all subsequent operations in the chain.
The <i>[translateXYZ]</i> object is used to move the image around.
Finally, the <i>[pix_draw]</i> object renders the pixel data to the screen.
<p>The patch mentions that changing the Z in <i>[translateXYZ]</i> does not
change the size of the image, as would occur with a <i>geo</i> object like
<i>[square]</i>.
This is because <i>[pix_draw]</i> simply draws the pixel at the current raster
position, without any transformation. If you want to change the size
on the fly and rotate the image, you need to texture map the pix, which
is described in the next section.
<p><img SRC="tribar.gif" height=13 width=561>
<h3>
<a NAME="pix_multiimage"></a>[pix_multiimage]</h3>
The <i>[pix_image]</i> object only loads in one image at time. If you
try to change the image rapidly while the patch is running, you will notice
a lag every time it has to load in a new file. To avoid this lag,
there is another object called <i>[pix_multiimage]</i>. If you look
at patch gem_pix/gemMultiImage.pd, you will see this object in action.
<p>Basically, the * in the file name is replaced by the number that you
pass in. This allows you to play sequences of images with random
access. The one downside is that every image is loaded into memory
when the object is created, so you need to have a lot of RAM to use it.
<p><img SRC="tribar.gif" height=13 width=561>
<h3><a NAME="pix_movie"></a>[pix_movie]/[pix_film]</h3>
These objects are used to read movie-files from disk (or if supported from the internet).
The movie is streamed off of disk,
using whatever decompression libraries are installed on your computer.
On Windows AVI movies seem to work fine,
but there is also a prelaminary support for quicktimes (and mpeg).
On macOS-X all formats supported by the system (basically: quicktime) should work ok.
On linux the support is highly depending on what libraries are installed during compile time.
There is support for MPEG (with libmpeg1 or (preferred:) libmpeg3),
quicktime (either libquicktime or quicktime4linux;
most likely you will not be able to decode quicktimes with proprietary codecs)
and AVI (with libavifile which is able to utilize windows-dlls for (proprietary) codecs).
There is also some rudimentary support for FFMPEG.
The right inlet of <i>[pix_movie]</i>
accepts a number to specify the frame to display. Look at 04.pix/04.movie.pd
for an image.
<p>A key fact of <i>[pix_movie]</i> is that it immediately sends the movie
data to OpenGL as a texture map. This means that you do not need
the <i>[pix_texture]</i> object in your chain. This also means that
you cannot process the movie data with pix objects. The main reason
for this is that it removes the need for a copy of all of the movie data.
If you want to apply some image-processing, you will have to use <i>[pix_film]</i>
(and <i>[pix_texture]</i> for texture-mapping).
<p>Some of the geos will not texture map the <i>[pix_movie]</i> data correctly.
Cone and sphere do not use texture coordinates when they are provided,
so when you display a movie on one of these objects, you will have a black
region (unless your movie size is a power of two...however, most movies
are 320x160 pixels or something). This will be fixed in a future
release.
<p><img SRC="tribar.gif" height=13 width=561>
<h3>
<a NAME="pix_video"></a>pix_video</h3>
The "image" can come from the <i>[pix_video]</i> object.
This means that you can use a real-time video source and display it on the screen.
<p>You can play with <i>[pix_video]</i> with the patches in 04.video/.
The patches are explained in more depth in the advanced section of the GEM manual.
<p><img SRC="tribar.gif" height=13 width=561>
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