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- - Image perspective effect in python (https://talk.maemo.org/showthread.php?t=9867)

Khertan

2007-09-19 09:08

Image perspective effect in python

Hi,

I'm trying to do a Apple's Coverflow like display, and so i'm trying to make perspective on an image.

I've successfully found how to do it, but it's really slow. For this i use pygame to display and load image and PIL to make perspective.

It's take at least one minute to calc 5 covers. I think most of the time is taken by the conversion of a pygame image to an pil image :

Code:

    def perspectiv(self,z,w):

      pil_string_image = pygame.image.tostring(self.origineimage, "RGBA",False)

      #pil_string_image = self.image.tostring()

      pil_image = Image.fromstring("RGBA",(250,250),pil_string_image)      

      pil_image = pil_image.transform((250,250),Image.QUAD,(0-w,-w,0-w,250+w,250+z,250+z,250+z,-z) ,Image.BICUBIC)

      mode = pil_image.mode

      size = pil_image.size

      data = pil_image.tostring()

      #assert mode in "RGB", "RGBA"

      self.image = pygame.image.fromstring(data, size, mode)

Do you know an other way to do fast perspectiv image effect in python ?

pipeline

2007-09-19 11:47

Re: Image perspective effect in python

For what's its worth, here's how i would -try- to optimize (never used these python functions).

Just from looking at the documentation at :
http://www.pygame.org/docs/ref/image.html and
http://www.pythonware.com/library/pi...book/image.htm

I would probably keep the original image strings in global array so i didnt need to frombuffer() before every frame. I would do this using the pygame.image.frombuffer() during intial setup only... subsequent accesses just write directly to the string buffer (i guess this is how it would work)

Additionally I would probably -try- to do the same thing with the destination image strings... keeping in global array and just use a third/temp string for transformation. Not sure if regular assignment to the buffers would keep links to image using them though.

So your render function might look like
TmpImageString = OriginalImageStrings[x]
TmpImage = pil_image.transform(...)
#Try uncommented first... if just setting the buffer string doesnt work, revert to original way.
#self.image = pygame.image.fromstring()
DestinationImageStrings[x] = pil_image.tostring()

Also not too sure about the 2d transformation function other than whats the performance difference using NEAREST or BILINEAR instead of BICUBIC? BICUBIC is the nicest/slowest and nearest is fastest.

Khertan

2007-09-19 11:55

Re: Image perspective effect in python

Thanks.

Since my post i've make some tests, deleted the conversion with StringIO and optimized use of image, use smallest cover 125x125 instead of 250x250, use NEAREST instead of BICUBIC.

But it's still too slow on the device to be usefull.

In fact, the most slower thing is PIL transformation.

zeez	2007-09-19 14:25

Re: Image perspective effect in python

Can you maybe post the whole source so i can take a look at it ?

Khertan

2007-09-19 14:47

Re: Image perspective effect in python

1 Attachment(s)

yes of course ... but it 's just a test a this time of 5 covers movig on the screen. It s really sadly coded !

Here the source (Sorry can't upload a complete zip as this forum only accept 96Kb max files):

Just get the cover i ve upload and duplicate it to "cover1.jpg" "cover2.jpg" "cover3.jpg" "cover4.jpg" "cover5.jpg" in a "covers" folder, located in the flow.py source code folder.

Code:

#!/usr/bin/env python



import os, pygame

from pygame.locals import *

import Image

import StringIO

import time



class Cover:

    def __init__(self, pos):

        self.image = pygame.Surface((125,125))

        #self.origineimage = image

        self.cover_url = os.path.join('covers/cover'+str(pos)+'.jpg')

        #print self.cover_url

        self.pil_image = Image.open(self.cover_url)

        #print self.pil_image

        self.speed = 5

        self.pos = self.image.get_rect().move((800 / 6) * (pos - 1 ), 50)

        #self.oldpos = self.pos

        #self.oldpos.left = self.pos.left - 999

        #print self.pos

        self.perspectiv(00,00)

        

    def move(self):

        self.pos = self.pos.move(self.speed, 0)

        if (self.pos.right > 800):

            self.pos.left = 0

            

        #if (abs(self.pos.left-self.oldpos.left)) > 25:

        #  self.oldpos = self.pos

        if (self.pos.left + 77)<400:

          leftangle = 0

          rightangle = (400 - (self.pos.left + 77)) / 2

        else:

          leftangle = ((self.pos.left+77) - 400 ) / 2

          rightangle = 0

        self.perspectiv(rightangle,leftangle)

        

                

    def perspectiv(self,z,w):

      #pil_string_image = pygame.image.tostring(self.origineimage, "RGBA",False)

      #pil_string_image = self.image.tostring()

      #pil_image = Image.fromstring("RGBA",(250,250),pil_string_image)      

      #pil_image = Image.open(self.cover_url)

      perspectiv_pil_image = self.pil_image.transform((125,125),Image.QUAD,(0-w,-w,0-w,125+w,125+z,125+z,125+z,-z))

      #mode = pil_image.mode

      #size = pil_image.size

      #data = pil_image.tostring()



      #assert mode in "RGB", "RGBA"

      #self.image = pygame.image.fromstring(data, size, mode)



      f = StringIO.StringIO()

      perspectiv_pil_image.save(f, "bmp")

      f.seek(0)

      self.image = pygame.image.load(f)

      f.close()

      

#quick function to load an image

def load_image(name):

    path = os.path.join('covers', name)

    return pygame.image.load(path).convert()





#here's the full code

def main():

    pygame.init()

    screen = pygame.display.set_mode((800, 480))



    #coverimg1 = load_image('cover1.jpg')

    #coverimg2 = load_image('cover2.jpg')

    #coverimg3 = load_image('cover3.jpg')

    #coverimg4 = load_image('cover4.jpg')

    #coverimg5 = load_image('cover5.jpg')

    

    #background = load_image('background.png')

    background = pygame.Surface((800,480))

    #Display Background

    screen.blit(background, (0, 0))



        #Define covers

    objects = []

    o = Cover(1)

    objects.append(o)

    o = Cover(2)

    objects.append(o)

    o = Cover(3)

    objects.append(o)

    o = Cover(4)

    objects.append(o)

    o = Cover(5)

    objects.append(o)

    

    while 1:

        for event in pygame.event.get():

            if event.type in (QUIT, KEYDOWN):

                return



        for o in objects:

            screen.blit(background, o.pos, o.pos)

        for o in objects:

            o.move()

            screen.blit(o.image, o.pos)



        pygame.display.update()







if __name__ == '__main__': main()

zeez	2007-09-19 15:59

Re: Image perspective effect in python

Hmm i'm afraid the transformation ist just too slow. I don't think it is possible to optimize it *heavily* without openGl. You could of course precache the transformations but for a common music collection on a 8GB card i don't think thats reasonable..

Khertan

2007-09-19 16:11

Re: Image perspective effect in python

I don't think too.

I ve tested raytracing algo too ... but really too slow ;)

Hum i'll think of a manual transformation by matrix on the image.

zeez	2007-09-19 16:22

Re: Image perspective effect in python

I'm pretty sure that's what the pil transform function does. And it is *a lot* of computation. We need openGL on the IT :)

muki	2007-10-16 16:03

Re: Image perspective effect in python

Me a novice to maemo dev but can't the DSP be used to do the transform?

konttori

2007-10-16 17:02

Re: Image perspective effect in python

hey, don't use PIL to do anything if at all possible. It's freaking slow. If possible by any means, just use pygame / add your own transformer function.

Or, consider this: Take the image to pygame. Make a copy of it. Scale the copy inside pygame to 40x40. Move that to PIL. Make the transformation in PIL. Take the image from PIL. Transfer it to pygame. Scale it to 250x250 in pygame. Phew. Relax. Should have taken much less time that way.

Also, consider doing less frames for the transformation and make it quicker. As it's quick, user might not notice the blurriness of the image because of the 40x40 base image.

konttori

2007-10-16 17:02

Re: Image perspective effect in python

Ahh, you might also consider evas. They should be good way to do the coverflow.

Darius2006

2007-10-18 10:54

Re: Image perspective effect in python

Hi,

would you like to join my py-navigator project.
car navigation made in python 2D/3D perspective
intelligent POI database managment and more.

Please contact me if you are interested.
Mayby Python is slow as a script language but give a chance to have more developers to work on the project.

Darius

Khertan

2007-10-19 11:27

Re: Image perspective effect in python

Hi,

Quote:

you might also consider evas.

Hum i ll try :)

Quote:

would you like to join my py-navigator project.

I'm sorry but i have too many project i must finish before. But Thanks.
And if you have some questions don't hesitate, i ll help you (if i can :) ).

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