Expert: Ran - 6/30/2009

Question
Hello!
I've been struggling with this for weeks! I am drawing a graphic novel in Manga Studio EX 3.0.  The pics are black and white (filled with gray tones).  When I export them to JPEG format they print out with square lines over top of the filled areas.  The pages look like plaid shirts!  I guess if I can import the JPEGs into CorelDraw to fill them I shouldn't have this problem.  
HERE'S MY QUESTION: How do I fill an imported JPEG in CorelDraw 12 without retracing my lines? (The files are just plain lines like a coloring book but too complex and time consuming to retrace.)
Can you PLEASE help me???!!  I gotta get help!  THANK YOU SO MUCH FOR YOUR TIME!!!

Answer
Hello Wyatt

CorelDraw is a vector drawing program. To do what you want you need to use a painting program (such as Photoshop). As far as I know, what you want to do is not possible in CorelDraw without retracing the lines (although the Trace tool is very good and might help you do what you want - in X4 click Bitmaps/Outline Trace/Line Art).

However I feel your 'plaid' issue is the actual problem here which wants fixing. The effect you mention is almost certainly a moire pattern, which is caused by interference between incompatible resolutions, e.g. 200dpi and 300dpi. So, I would make sure the image being exported from Manga Studio is 300dpi, which is CorelDraw's native resolution (although it can be changed in the Options dialog).

I'll also mention that sometimes I've seen moire effects onscreen which aren't present when the image is printed. Usually you can spot these because the moire pattern changes its appearance when you use a different screen magnification.

Please let everyone know how you get on and if any of this helps.

* * FOLLOWUP * *

Thanks indeed for your kind words! Last night as I was thinking about this, another thing struck me. I think your Manga program is "rasterising" its output file, i.e. instead of a plain fill of, say, 50% grey it is producing a .JPG containing a halftone pattern of dots, to simulate a 50% fill. This is far from ideal because the rasterising should happen in the printer. See if you can change this setting in the Manga preferences, or try another output file type. For more info, see the description of Resolution on my company website here:

http://www.newhorizons.co.uk/press/jargon.htm

The Resolution part is at the bottom but if you do the maths you can work out a resolution to use which will avoid the plaid effect (hopefully!)

All the best

Randal