If you are using image thumbnails and the popup enlargement feature then there is a need for Simple:Press to know the dimensions of the image – particularly the width. If the image in question has been uploaded to your server and is, as such, an ‘attachment’, then the dimensions will be known. But there can be issues surrounding the use of a remote image, embedded into a forum post using the editor toolbar ‘image’ tool.
When such a remote image is included into a post, the editor dialog attempts to read from the remote server to ascertain the dimensions of the target image. If all goes well the system itself will fill in these details. However, success is dependant upon your servers ability to grab this sort of data from remote servers. This requires a php setting named ‘allow_url_fopen’ to be turned on which allows this activity to take place.
If this setting is turned off – and some hosts do prefer to have it set to off – then Simple:Press can not ascertain missing image dimensions. This means that the popup enlargement feature will be turned off for that image. This explains why the feature does not work with some remote images. It will be because the dimension attributes are missing from the image tag in the forum post.
If you see, instead of the image, a message saying that the ‘Image can not be found’, this does mean that (a) ‘allow_url_fopen’ is turned on and (b) after interrogating the target server the image file seems to be genuinely not there.
If, on the there hand, you see nothing where the image should be then the same applies except it means that ‘allow_url_fopen’ is turned off but the normal http request to the remote server failed to locate the image file.