Added img basename explainer

README.md

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-# web-proposals
+# Web Proposals
+
+This is a grab-bag of various web proposals, both HTML and CSS.
+
+## IMG `basename` attribute
+
+The IMG `basename` attribute is an attribute specified on the IMG element,
+which allows the developer to assist the User Agent in specifying the name of
+this image. This is used when the User Agent allows the user to download the
+image, either via "Save Image" dialog option or drag-and-dropping it into a
+directory on the machine.
+
+[initial proposal](https://github.com/whatwg/html/issues/2722)
+[explainer](https://github.com/vmpstr/web-proposals/blob/main/explainers/img-basename.md)
+
+## Display Locking
+
+[dedicated repo](https://github.com/WICG/display-locking)
+
+## Shared Element Transitions
+
+[dedicated repo](https://github.com/WICG/shared-element-transitions)

explainers/img-basename.md

@@ -0,0 +1,31 @@
+# IMG `basename`
+
+## Summary
+
+The IMG `basename` attribute is an attribute specified on the IMG element. It
+indicates the basename of the filename to use when the user saves the image,
+either via "Save Image" dialog option or by drag-and-dropping the image to the
+system directory.
+
+## Details
+
+* [Initial proposal and discussion]([initial proposal](https://github.com/whatwg/html/issues/2722)
+
+It is common for images to be served from servers that obfuscate filenames to
+optimize storage. In this case, the User Agent uses the obfuscated filename as
+the suggested filename to use when saving the file.
+
+It is also possible that images come from a `data:` url, meaning that they
+don't have a filename associated with them. In this case, the User Agent
+selects a filename arbitrarily, with `download` and `unknown` being common
+choices.
+
+In either case, a better user experience would be to have developers specify
+the basename to use, since developers have contextual information for the type
+of image being downloaded. This is the proposal for the `basename` attribute.
+
+Note that since the extension of the filename can be determined automatically
+by the User Agent, we feel that the choice should not be in the developer's
+options to avoid security problems (e.g. developer picking `.exe` as an
+extension for the image which can cause inadvertent code execution by the
+user).