Re: Replacing the animal photos in the ‘erase’ activities

[Karl Ove Hufthammer]

Timothée Giet skreiv 20.02.2022 15:43:
> Le 20/02/2022 à 15:21, Karl Ove Hufthammer a écrit :
>> I have some comments and questions about the animal photos in the
>> ‘erase’ activity.
>>
>> […]
>>
>> Would you mind if I replaced them with some new/better ones?
> Hi Karl,
>
> The issue with changing those photos, or why I didn't do it already, is
> that replacing those photos with high resolution ones will take much
> more storage space for sure. And as we are already close to the size
> limit for apks on the play store, we need to be careful with adding more
> big files.

I see. I‘ve done some experimenting, and I think we can achieve a 
compromise regarding file size and image quality. For high resolutions, 
even quite heavy JPEG compression (e.g., 60%–70%) doesn’t give *too* 
much quality loss – and certainly much better quality than having low 
resolution images and scaling them up.

And rescaling medium-resolution images also gives acceptable results. So 
if we use either full resolution (1920 × 1080) with very high 
compression *or* medium resolution (1600 × 1900 or 1440 ­× 810) with 
medium compression, I think we should be able to replace the existing 
images (at least the larger ones) without increasing the overall file 
size. I’m not sure exactly where the sweet spot regarding resolution and 
level of compression is, so this needs a bit more experimenting.

Things that help are images with not too much detail, so photos with 
blurry backgrounds should work well.


> Else, one thing that could be done for now is to replace the images with
> fewer ones of in 1920*1080, taking care that the total size doesn't
> increase much compared to current ones (that is around 5.4Mio).

Reducing the number of images but increasing their quality (both image 
quality and content quality) sounds like a good solution. :)

I can create some scripts to automatically resize and recompress the 
images to a given resolution and compression level. And if we keep the 
original files, we can increase the file size / quality when the becomes 
possible.

I guess the first step is for us to agree on a new, smaller set of very 
high-quality images.


> About licenses, the best would be photos in Creative Commons CC-BY or
> CC-0, or else CC-BY-SA 4.0.
Good. I see that Wikimedia Commons have some nice animal images with 
these licenses:
https://commons.wikimedia.org/wiki/Commons:Featured_pictures/Animals

And there are also (almost too) many CC-licensed images at Flickr.


-- 
Karl Ove Hufthammer