Export as JPEG can produce a format unaccepted by other photo tools - cause detected?

[Wilhelm Sanke]

On Tue Apr 17, 2007, Chipp Walters chipp at chipp.com wrote:

> Hmmm.
> Never tried that Wilhelm. I've always used the 'export img x to file y as
> JPEG' form. Though there is another issue with JPEG export. Setting the
> JPEGquality to 100 doesn't create a very good JPEG image. Try this, 
> create a
> picture of a red box inside a blue box in Photoshop. Save it as JPG 
> maximum
> (100), then save it as PNG as well. Then import the PNG version into 
> Rev and
> export is with JPEGquality at 100. You'll see the JPEG exported from
> Photoshop is much nicer than the export from Rev.
>
> best,
> Chipp



I repeated your steps above and see that the "border" between blue and 
red is somewhat blurred and also the hue is somewhat different. This 
seems to me to be another problem of image processing in Rev, but maybe 
not necessarily connected to the format issue I reported.-

I did some further testing and found out that up to version 2.5 of 
Metacard (cannot remember the corresponding Rev version at the moment, 
but it was in 2003) the two forms of syntax

export JPEG to URL "binfile:next.jpg"

 and

export jpeg to file tFilename

produced JPEG files that could also be read by PainShopPro etc., but 
after that - since Metacard version 2.5.1 - these files could only be 
used and processed inside Rev/Metacard itself.

The same problems hold for PNG files and the "export PNG..." syntax.

The related cause does not seem to be the "Endian issue", i.e. the 
change of the order of colorchars in the imagedata that occurred between 
Metacard versions 2.4 and 2.5, because the "export JPEG..." syntax works 
both for Metacard 2.4 and 2.5. So something else was changed in version 
2.5.1.

I thinks the docs both for Rev and Metacard should be updated and the 
faulty commands abandoned as we have the working  'export img x to file 
y as JPEG' form' and "export snapshot".--

Another observation not directly related to the above issue:

While the speed for numerical computations has evidently been improved 
from Rev engine 2.6.1 to Rev 2.8.1-dp2, imagedata processing on the 
other hand has slowed down. Some of my scripts that process imagedata 
run up to 40% slower with engine 2.8.1.-dp2 (as similarly also in the 
other engines since Rev 2.7).-

Thanks for the response.

Best,
Wilhelm

<http://www.sanke.org/MetaMedia>