Sorry for the empty posting, my mail system ran a glitch.
This is what should have been sent:
> Scott England wrote:
>
> I have a map window, that I have set through code to be 8 x 7 inches.
> Why, when I save the map window to a JPEG using the same proportions
> and then open it in a 3rd party graphics package, does it say that it
> is actually 26.48 x 23.17 inches at 29 pixels per inch??
This seems strange indeed. I believe it has something to do with how
your screen resolution is translated into the jpeg engine.
Remember that you will get no more than screen resolution (typically 96
dpi) when you save a window in this way. Printing, or viewing this image
any bigger will reduce apparent resolution.
But you can increase resolution by opting to save the window as a custom
larger size. You increase width, height will follow for same ratio.
This will produce a larger file, but used in the original size, the
image will appear to have a resolution of 4x96=384 dpi, sufficient for
most printers.
MapInfo can save windows in a variety of formats, and I do not believe
that jpeg is the most suitable. This compression technique is best fit
for photograps.
When used on images with evenly colored areas, with sharp borders such
as maps, a 'rippling' effect occurs where areas adjoin. Some color
information spills across the border.
This effect increases with compression - a parameter you cannot control.
MI version 4.5 seems to have used a larger factor than present 5.5 where
the effect is not noticeable. But jpegs get bigger.
I just tested this:
MI version 5.5 eng.
Input: Standard World map, displayed full screen on a 14" monitor.
Output: Saved window to 100 cm (�40") width.
File formats and size: tif 26542 kB took a LONG time to save
jpg 2553 kB
psd 1035 kB
wmf 305 kB saving almost instantaneous
png 148 kB !!
OK - so what about quality?
Well I brought them all up in PaintShop, in 1.1 viewing scale.
No differences can be seen at all! I find this astonishing!
Bear in mind that this test was performed on a simple map with few
colors.
But the example goes to show that file sizes can vary considerably
depending on format, without any notiecable difference in image quality.
Regards, Mats.E
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