image_get_intermediate_size() may return wrong thumbnail size

[chipbennett]

See ​this WPSE question for a more detailed explanation of the problem.

Essentially, if get_the_post_thumbnail() is passed an array for the $size argument, and if two images have one dimension exactly the same, the image with the smaller opposing dimension will be returned, even if the dimensions for the other image are declared explicitly.

The issue appears to be due to the way that image_get_intermediate_size() determines if an image exists that is cropped to dimensions similar to the specified $size array. As soon as it finds one, it uses it.

I've attached a patch that first attempts to find an image cropped exactly on both dimensions, before looking for images cropped exactly only on one dimension. There will still be edge cases where the wrong image might be returned, but I'm not sure of the most efficient way to handle such cases.

(Note: props to Rarst for finding the underlying issue.)

slight modification to image_get_intermediate_size()

I've ran into this issue myself.

I'm trying to work out the best way to cover the remaining edge case. For example, two image sizes have the same width, but different heights. In this case, the image size with the smaller height will return, even if the image size with the larger height has a height that is smaller than the height specified in the $size array.

My thinking is that, if $imagedata['sizes'] can be sorted from high to low on the variable dimension, before looping through the sizes, then the largest, rather than smallest, image would be returned.

Would a function like this work, prior to looping through the images?

// sort $imagemeta['sizes'] descending by width, height
function compare_sizes( $a, $b ) {
	$sorted = strnatcmp( $a['width'], $b['width'] );
	if( ! $sorted ) return strnatcmp( $a['height'], $b['height'] );
	array_reverse( $sorted );
	return $sorted;
}
usort( $imagedata['sizes'], 'compare_sizes' );

(I'm a bit out of my depth on this one, with sorting associative arrays. If there's a better way to do this, I'm all ears.)

You can use ​uasort().

@scribu should I update the patch to use uasort() instead of usort()?

Replaced usort() with uasort(), per @scribu's recommendation

Note that, even if you define the compare_sizes() function inside the if, it's still created globally.

Better to define it outside of image_get_intermediate_size(), as a private helper function - that is to say with a leading underscore: _compare_sizes(), or something even more obscure, to prevent collisions.

Replying to scribu:

Better to define it outside of image_get_intermediate_size(), as a private helper function - that is to say with a leading underscore: _compare_sizes(), or something even more obscure, to prevent collisions.

Done in 17626.patch​.

Related: #18532

Related: #18799

Hey scribu, any chance we can move on this one?

One question: in _compare_imagedata_sizes(), why is strnatcmp() used to compare the dimensions (which are just numbers)?

Replying to scribu:

One question: in _compare_imagedata_sizes(), why is strnatcmp() used to compare the dimensions (which are just numbers)?

Not sure? Probably because it worked, and I wasn't aware of a better method? :) I can change it though. Suggestions?

Just use plain comparison operators: <, >, =, as in the uasort example: ​http://php.net/uasort#example-4584

Noticed an inconsistency in the comments: $imagemeta['sizes'] should be $imagedata['sizes'].

In [20696]:

Have the $fields argument for XML-RPC's wp.getPostType, getPostTypes, wp.getTaxonomy and wp.getTaxonomies take the names of the post type or taxonomy object keys that will be returned.

• capabilities becomes cap
• object_types becomes object_type

fixes #17626.

[20696] was meant for #20566.

Re-opening, and also punting.

Related: #21004

I'm running into this bug, and it's driving me crazy.

• Client uploads a 208*60px image for use in the Image Widget plugin
• Thumbnail size is set to 120*120px
• WP creates a 120*60px version of the image
• image_get_intermediate_size returns the 120*60px one, even though $size is array(208,60)
• Wrong image show in widget

I'm forced to use WP 3.4.2 (which means the plugin uses legacy media lib code) for now, but can reproduce the problem with trunk by calling wp_get_attachment_image directly.

@nacin Any suggestions? I think image_get_intermediate_size should either work with cropped images, or filter them out completely. In the first case, "area" is no longer a valid metric (a 400*100px and a 100*400px crop of the same 400*400px image have the same area).