Filename truncated when f=jpeg

[oo12]

Using the phpThumb option f=jpeg when phpthumbof.hash_thumbnail_names is set to No (default) causes 5 characters to be stripped off the end of the filename in an attempt to remove the extension. For images with a 4-character extension (i.e. .png or .jpg) this results in the final character of the base filename being removed. In some cases this causes problems: 1.png becomes .jpeg (won't display) or image-1.png and image-2.png both become image-.jpeg.

While f=jpg works and doesn't trigger the bug, according to the phpThumb documentation, jpeg is the correct value for the output image format parameter.

The problem is caused by these lines.