wp-includes/media.php

Retrieves the current attachment object from the $post global.

This implements the functionality of the Gallery Shortcode for displaying WordPress images on a post.

The filter 'get_image_tag_class' allows for changing the class name for the image without having to use regular expressions on the HTML content. The parameters are: what WordPress will use for the class, the Attachment ID, image align value, and the size the image should be.

The second filter 'get_image_tag' has the HTML content, which can then be further manipulated by a plugin to change all attribute values and even HTML content.

This is so that the image is a better fit for the editor and theme.

The $size parameter accepts either an array or a string. The supported string values are 'thumb' or 'thumbnail' for the given thumbnail size or defaults at 128 width and 96 height in pixels. Also supported for the string value is 'medium' and 'full'. The 'full' isn't actually supported, but any value other than the supported will result in the content_width size or 500 if that is not set.

Finally, there is a filter named, 'editor_max_image_size' that will be called on the calculated array for width and height, respectively. The second parameter will be the value that was in the $size parameter. The returned type for the hook is an array with the width as the first element and the height as the second element.

Array with image url, width, height, and whether is intermediate size, in that order is returned on success is returned. $is_intermediate is true if $url is a resized image, false if it is the original.

The URL might be the original image, or it might be a resized version. This function won't create a new resized copy, it will just return an already resized one if it exists.

A plugin may use the 'image_downsize' filter to hook into and offer image resizing services for images. The hook must return an array with the same elements that are returned in the function. The first element being the URL to the new image that was resized.

The $size parameter can be an array with the width and height respectively. If the size matches the 'sizes' metadata array for width and height, then it will be used. If there is no direct match, then the nearest image size larger than the specified size will be used. If nothing is found, then the function will break out and return false.

The metadata 'sizes' is used for compatible sizes that can be used for the parameter $size value.

The url path will be given, when the $size parameter is a string.

If you are passing an array for the $size, you should consider using add_image_size() so that a cropped version is generated. It's much more efficient than having to find the closest-sized image and then having the browser scale down the image.

Both attributes are required in the sense that both parameters must have a value, but are optional in that if you set them to false or null, then they will not be added to the returned string.

You can set the value using a string, but it will only take numeric values. If you wish to put 'px' after the numbers, then it will be stripped out of the return.

The returned array has the file size, the image width, and image height. The filter 'image_make_intermediate_size' can be used to hook in and change the values of the returned array. The only parameter is the resized file path.

The PNG transparency will be preserved using the function, as well as the image type. If the file going in is PNG, then the resized image is going to be PNG. The only supported image types are PNG, GIF, and JPEG.

Some functionality requires API to exist, so some PHP version may lose out support. This is not the fault of WordPress (where functionality is downgraded, not actual defects), but of your PHP version.

Calculate dimensions and coordinates for a resized image that fits within a specified width and height. If $crop is true, the largest matching central portion of the image will be cropped out and resized to the required size.

Allows a plugin to replace the content that would otherwise be returned. The filter is 'img_caption_shortcode' and passes an empty string, the attr parameter and the content parameter values.

The supported attributes for the shortcode are 'id', 'align', 'width', and 'caption'.

If either width or height are empty, no constraint is applied on that dimension.

While $size will accept an array, it is better to register a size with add_image_size() so that a cropped version is generated. It's much more efficient than having to find the closest-sized image and then having the browser scale down the image.

A mime icon for files, thumbnail or intermediate size for images.

Checks to make sure that the embeds library hasn't already been loaded. If it hasn't, then it will load the embeds library.