Optimising a web site with an SEO perspective means respecting coding standard to make sure search engine understand the information you are providing them. Let study into more details rules for images /pictures indexing. Photos’ meta information and other parameters help search engines to index pictures. This work can be important to appear indexed in google or bing images and is a practice rewarded by search engines because it is considered useful for the user experience.
First of all, to optimise photos, you need to follow the same principle as the text link. When you scroll over a photo with your mouse, a text can appear. This text helps search engine to identify what the photo is about.
To images optimisation, you just need to implement alt parameters to img tag for every photo/image:
img src=”/imagedirecotry/imagename.png” width=?width? height=?height? alt=?description?
It’s also important to name images using keywords describing a photo and if possible including keyword(s) you want a page to show up on search engines. The correct way to name is using same rules as url rewriting: max 5 words, separated by “-“, lowercase letters, without accents and avoiding special characters.
Format and quality of images is another important variable. Search engines consider GIF (at 256 colors) or PNG 8 the format for graphic images and JPG or PNG 24 the format for pictures with millions of colors. Moreover they look at size and so, the optimisation of these format to show a good image not so heavy to load is key. Indeed, average time to load a page is included in Google algorithm. Therefore, pictures included on a website should be resized to respect, space and number of pixels available in the content to include the image.
To conclude this process, do not forget to share images in various online tools to index images (like Flickr, Webshots, …) and in generalist social networks (like Facebook, Twitter, ….). Sharing a selection of images with appropriate comments and tags will help position them on the search engines.