[visionegg] Re: Paletted BMP files of different sizes
- From: Andrew Straw <astraw@xxxxxxxxxxx>
- To: visionegg@xxxxxxxxxxxxx
- Date: Thu, 09 Oct 2008 11:41:53 -0700
Tim Blanche wrote:
> Hello,
>
> I need to present a series of 100 or so images, not a movie, but briefly
> flashed images separated by 1~3 seconds.
>
> The "image_sequence_fast.py" demo almost does the job, with the
> following two issues:
>
> i) The BMP images I have are paletted, but Textures.py raises a error
> "Paletted images are not supported". Quick work-around was to convert
> the image into 24 bit RGB colour, but I was wondering if there's a
> better way?
>
Not in the current VE version. I've just updated the svn version (r1508)
of VE to support paletted images, but if your own code already does the
conversion, this is hardly a reason to upgrade.
> ii) the images do not have all the same pixel dimensions, so the
> single-texture-with-a-fixed-size approach used by the demo code isn't
> suitable. A not-so-quick work around would be to re-size all the images
> to have the same dimensions as the largest image in the set, with border
> padding the same as the background colour, but again, there must be a
> better way.
>
Yes. Make a texture big enough for your biggest image and then use
put_sub_image() to place your images in it. Then, the tricky bit is that
this is a little beyond the scope of the abstractions in
VisionEgg.Texture. Basically, a TextureStimulus (the thing Vision Egg
draws) hold a Texture (abstracting the image data) which holds a
TextureObject (abstracting the image data on the video card). You have
to make sure they play nicely together. This means, since the
put_sub_image() call short-circuits all but the TextureObject, you have
to manually update the relevant part of the other stuff. In this case,
this is the size parameter of the TextureStimulus and the buf_rf and
buf_tf (buffer right fraction and top fraction) of the Texture. I'm
attaching a modified image_sequence_fast.py demo to show this.
-Andrew
--
Dr. Andrew D. Straw
California Institute of Technology
http://www.its.caltech.edu/~astraw/
#!/usr/bin/env python
"""Display a sequence of images using a pseudo-blit routine.
This is a fast way to switch images because the OpenGL texture object
is already created and the image data is already in system RAM.
Switching the image merely consists of putting the new data into
OpenGL.
Currently, there is no support for ensuring image sizes remain
constant, so if you get strange behavior, please ensure that all your
images are the same size.
"""
from VisionEgg import *
start_default_logging(); watch_exceptions()
from VisionEgg.Core import *
from VisionEgg.FlowControl import Presentation, FunctionController
from VisionEgg.Textures import *
import Image, ImageDraw
import OpenGL.GL as gl
num_images = 3
duration_per_image = .2
image_size = (256,256)
# Generate some images
image_list = []
for i in range(num_images):
image = Image.new("RGB",image_size,(0,0,255)) # Blue background
draw = ImageDraw.Draw(image)
line_x = image_size[0]/float(num_images) * i
draw.line((line_x, 0, line_x, image_size[1]), fill=(255,255,255))
image_list.append(image)
image_list.append(Image.open('/home/astraw/src/motmot/fview/motmot/fview/fview.gif'))
num_images = len(image_list)
screen = get_default_screen()
# create a TextureStimulus to allocate memory in OpenGL
stimulus = TextureStimulus(mipmaps_enabled=0,
texture=Texture(image_list[0]),
size=image_size,
texture_min_filter=gl.GL_LINEAR,
position=(screen.size[0]/2.0,screen.size[1]/2.0),
anchor='center')
viewport = Viewport(screen=screen,
stimuli=[stimulus])
p =
Presentation(go_duration=(num_images*duration_per_image,'seconds'),viewports=[viewport])
# Use a controller to hook into go loop, but control texture buffer
# through direct manipulation.
texture_object = stimulus.parameters.texture.get_texture_object()
def put_image(t):
i = int(t/duration_per_image) # choose image
im = image_list[i]
texture_object.put_sub_image( im )
w,h = im.size
stimulus.parameters.size = (w,h)
tex = stimulus.parameters.texture
tex.buf_rf = float(w)/tex.size[0]
tex.buf_tf = float(h)/tex.size[1]
p.add_controller(None,None,FunctionController(during_go_func=put_image))
p.go()
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