jpegs are not exported cleanly

[Jason Karney]

Hi,

I am trying to export a very basic Draw image as a jpeg. The image is 25 small
squares, fill/no outline, rotated, and arranged in a diamond shape on a white
background. (A diamond of diamonds, so to speak.)

I have tried all the options, and cannot get it to export cleanly. The squares
either look slightly deformed with wiggly outlines, or I end up with odd little
lines, like pixels extending from the squares. In contrast, I was able to
recreate and export this image without error in Freehand.

Looking back through this newsgroup, I have the impression that this problem is
one that may have been fixed in version 9. Does anyone know if that's the case?
Most of my illustration work will be used online, so Corel Draw's export
capabilities are of concern to me before I upgrade.

Thanks.

Jason

[Marko Jotic]

Jason,

This is a known problem in 8 that was fixed in 9. In version 8 the best
solution is to export oversampled (I am not sure to what level you have
to) as a cpt file (photopaint), open that, and resmaple it down.

Marko

[Serge Fateeff [C_Tech]]

Jason,

This is bug in CorelDRAW8's RIP. Fixed in 9.

Workaround: Since it affects only vector objects, you can
- save your file
- scale entire drawing to 200% (look for outlines)
- convert entire drawing to single bitmap
- scale this bitmap to 50%
- export to TIFF or any other desired bitmap format.

Ugly, but workable.

--

Serge

[Jason Karney]

Thanks all for your responses.

I had tried Serge's technique already, and played with different export options,
but the results were still the same. A GIF export produces the same kind of result.
I haven't tried Marko's solution using the PhotoPaint format; I have read that
PhotoPaint can handle imports a little cleaner, although importing my drawing into
there seems to produce the same "dirty" results.

Jason

[Mark Alger]

Jason;

Here's something that may be contributing to your problem.

The JPEG algorithm tokenizes each color in the file according to its RGB
values. The more different values there are, the more likely there will
be artifacts. Additionally, a high level of compression will tend to
posterize a compressed image, rendering it in fewer steps of gray than
the original.

When a vector image is converted to bitmaps, any lines are smoothed by a
process known as anti-aliasing. This trick uses intermediate colors
between to areas of different colors to "smooth" the edge. Can you see
where I'm heading?

If the edge between two colors in a rectangular grid is not EXACTLY on a
pixel boundary, then the edge will be anti-aliased, (unless you turn aa
off in the export, which you may not want to do). This means that, in the
export process, more tones are introduced into the image than were
intended, and, depending on the optimization method and the compression
ratio used, the intermediate-toned edge pixels will tend to be pressed
toward one of the pre-defined "steps" in the allowable palette.

The trick? Make sure that your edges fall EXACTLY on a pixel boundary.
How? Make the image in a bitmap editor. <eg>

If that sounds like too much work, then you need to decide exactly how
finicky you want to be.

--
Egads,
Wiz
Mark Alger
C_Tech

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