Display image thumbnails

[Antonio Cuni]

Hi,

I am developing an app which, among the other things, needs to display the pictures taken from the camera.

Currently I am using AsyncImage to load and display the images in a specific folder; something like this:

import sys

import glob

import os.path

from kivy.app import App

from kivy.factory import Factory

from kivy.lang import Builder

Builder.load_string('''

<Thumbnail@AsyncImage>:

   canvas.before:

       Color:

           rgb: 0.1, 0.1, 0.1

       Rectangle:

           pos: self.pos

           size: self.size

    size_hint: 0.25, None

   height: self.width

<PictureGrid@StackLayout>:

   spacing: "2dp"

''')

class PicShowApp(App):

    def build(self):

       root = Factory.PictureGrid()

       dirpath = sys.argv[1]

       files = glob.glob(os.path.join(dirpath, '*.jpg'))

       for f in files:

           root.add_widget(Factory.Thumbnail(source=f))

       return root

if __name__ == "__main__":

   app = PicShowApp()

   app.run()

However, I noticed that the process consumes an incredible amount of memory (I measured ~1GB to display 8 3840x2160 images).

I investigated and I saw that even if the AsyncImage widget are tiny, they keep a reference to the whole, full-resolution, uncompressed texture.

One thing I tried was to create the thumbnail whenever we change the texture of AsyncImage:

class MyAsyncImage(AsyncImage):

    def on_texture(self, obj, texture):

       if texture.size > tuple(self.size):

           buf = BytesIO()

           texture.save(buf)

           buf.seek(0)

           img = PILImage.open(buf)

           img.thumbnail(self.size)

           newtex = texture.create(size=self.size)

           newtex.blit_buffer(img.tostring(), colorfmt=img.mode.lower())

           self.texture = newtex

           self._coreimage = None

However, it doesn't work because I get garbled images. I suppose that I do something wrong to create the texture from the PIL image.

I know that I could simply save the thumbnails on disk and display those (and I might go for this solution after all), but now I would like to know if there is a solution which does not require to save data to disk.

So, basically I have two questions:

1) What is the best way to achieve my goal?

2) What is wrong in the MyAsyncImage example? How do I convert a PIL image to a texture?

thank you,

Antonio

[ZenCODE]

You definitely want to set the 'asyn_image.nocache=True' to prevent a cache buildup. But not sure if that will solve your issues. I did something similar below, but used the CLock to do background disk image creation that you are trying to avoid. Here it is anyway...

https://groups.google.com/forum/#!searchin/kivy-users/thumbnails/kivy-users/tMxkr6_0dB0/kzH8E5RrBQAJ

Good luck

[Antonio Cuni]

Thank you,

at the end I choose exactly this strategy. I found that opening the image with PIL+create/save the thumbnail+load the thumbnail is much faster than loading the big image directly. And it's even faster the second time, because the thumbnail has already been created :)

ciao,

Anto

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