How to avoid requesting images of all resolutions

[tianzhich]

I found an option removeAlternativeImages that could be used to remove images for alternative screen resolutions. However, even after enabling this option, images for all resolutions are still requested. I noticed in the code that it handles the srcset attribute of the images, but there is no option to disable this behavior.

[tianzhich]

This will help to improve the speed of saving with singlefile, avoid downloading images in all resolutions on websites where resource downloads are slow.

[tianzhich]

Hi @gildas-lormeau what do you think?

[gildas-lormeau]

Indeed, I agree with you that it's something to be desired. Unfortunately, from a technical point of view, when SingleFile processes srcset attributes, it doesn't know for sure whether it will be able to load the displayed image. That's why this issue exists. To get around it, I've added a hidden option blockAlternativeImages, which you can activate by following this procedure: https://github.com/gildas-lormeau/SingleFile/wiki/Hidden-options. This new option will be available in the next version.

[tianzhich]

when SingleFile processes srcset attributes, it doesn't know for sure whether it will be able to load the displayed image.

Why doesn't it know? Are you referring that some image tags only have the srcset attribute set but not the src attribute as a fallback? In that case, not requesting the image resources defined on srcset would cause issues, right?

If that's the case, can we check like this: similar to the removeAlternativeImages option, when blockAlternativeImages is enabled, only block the request to the resources defined in srcset if the src attribute exists. If src does not exist, the resources in srcset will still be requested.

[gildas-lormeau]

I'm referring to the case where for some reasons the server would refuse to serve the image defined in the src attribute. The case you mentioned should work even with blockAlternativeImages set to true.