We start with our scanned lineart. I ink my lineart prior to scanning to make sure the lines are crisp and clear so photoshop has no problem selecting them. Make sure the mode is set to RGB color.
Click on the icon indicated by the red arrow and make the layers you need and name one "Lienart" Or something similar.
Click the channels tab then click and drag the blue channel to the indicated icon, which will make a "Blue copy" channel. Then click the layers tab.
Make sure the "Lineart" layer is selected then click Select> load selection. In the channel box click and select "Blue Copy" And make sure the check box called "Invert" below is filled. Click "OK" and now you should see all your lines selected with the moving dotted lines.
Select the lasso tool or the magic wand tool (What ever they are called :P I'd wager any selection tools would do for this ^^) Then right click on the pic and in the menu you should see an option called "Make Work Path" Click it and make sure the setting in the box is 2.0 then click "OK". Now, click the paths tab and right click on the work path. Select "Fill Path". Use = black, mode = normal, and opacity = 100%. Click "OK" Once thats done right click on the path again and click "Delete Path" then click on the layers tab.
Now select the "Background" layer and then select your eraser tool. Make it's size as large as it can get and make sure you click the small icon the arrow is pointing at to make sure the fore and background colors are black and white. White needs the be the background color in the swatches. Just the way it is in the pic above.
Then you simply erase everything on the background layer leaving everything in the lineart layer untouched. The result is smooth and slender lines.
Here's a close up. As you can see, there are a few gaps in the lines that will make filling and selecting difficult. This can be fixed easily by selecting the brush tool with black color on the lineart layer with the brush size at one pixel. Just trace along the gaps to close them and make your traced lines as smooth as possible.
There you have it. Smooth closed lineart ^^ I hope this tutorial helps ^^ If you have any tutorials, just send them my way at FurroticDreams@yahoo.com