Well, I paste the code in image.php and then enable options of Artist and Image Credit on hte backend (options > image.
But everything is still same...

By the way, what I want to do is that If is it possible to show the name of USER, who upload image. That's all!

Have you enabled the filter-new-objects plugin? Otherwise this information is not known. If you have enabled the plugin the name is added to the description.

@sbillard:
Hi, well I have enabled the filter-new-objects plugin and then then enable options of Artist and Image Credit on hte backend (options > image. but nothing happens.

Even I try to use the echo $_zp_current_image->get("EXIFartist"); on image.php. But still nothing!

Well, if that EXIF field is not used on your image it is of course empty...

1. Obviously my image has author name in the image.
2. as sbillard say enabling filter-new-objects plugin will show uploader name but nothing working. perhaps this plugin have nothing to do with EXIF..

1. Then you did something wrong. Look at the database if the field has an entry.
2. That was for adding the USER who uploaded the image to the image info data. This of course happens only for newly uploaded images.

2. I just uploaded an image now , plugin is enables but no user information in descrption of image or in exif data.

Even I tried refreshing metadata

So, lets be clear. If you want the name of the person who uploaded the image you use the plugin. That is NOT the EXIFartist field. The name is appended to the description (like I said in my original post!)

If you want some other filed, like the EXIFArtist or IPTCByLine (they are different, by the way, but some software does not show you the distinction) the field from the metadata, then that field MUST exist in the image metadata and Zenphoto MUST have supported the field when you last imported the image metadata.

So, if you have refreshed your metadata and do not see that field, it is not present in your images metadata.