[visionegg] Re: mysterious image borders

Gary Lupyan wrote:
> Hey all.  I have this odd problem w/ image artifacts.  For some image
> file-monitor combinations a row of black pixels appears along one or
> several of the image edges. This makes it impossible to have the image
> appear seamlessly on a background (that is, when the background of the
> image and the background of the screen is matched, the row of pixels
> showing up screws up the seamless presentation of the image on the
> background.
>
> Image format (bmp, png) doesn't matter.  Image placement on the screen
> doesn't matter (the artifacts still appear).
> Image size DOES matter.  Slight changes in size can make the borders
> go away, but it's a trial and error procedure.
Hi Gary,

This is mostly likely a graphics card dependent scaling issue. The best
thing to do will be to attempt to get rid of all graphics-card scaling
-- set your image sizes to powers of 2 (e.g. 1024 by 512 pixel images).
Other than that, if you can send some sample code that demonstrates the
issue, I can attempt to take a look at it.

Also, try playing with the texture_mag_filter, texture_min_filter,
texture_wrap_s, and texture_wrap_t parameters of the TextureStimulus class.
>
>
> Couple other questions:
> 1. is there a way to display palettized images using texture stimulus?
Yes, I think if you simply pass a PIL Image instance of a .gif or other
palletized instance, the VE should automatically convert it to RGB. Or
are you suggesting pass the acutal palletized data to the graphics card
and have it do the color lookup? There's no support for that.
> 2. Is there a way to resize images using texture stimulus? (I know
> there are other ways of resizing)
Yes. Simply change the "size" parameter of the TextureStimulus. This
will change the display size without changing the internal storage,
which is determined by the texel data out of which the Texture was created.

-Andrew

-- 
Andrew D. Straw, Ph.D.
California Institute of Technology
http://www.its.caltech.edu/~astraw/

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