Re: [ferret_users] Publication quality image export question

["William S. Kessler" <william.s.kessler@xxxxxxxx>]

There is no way that gif output can be good enough for publication  
graphics. I think you are trying to do something that can't be done.  
Gif plots from Ferret are exactly what you see on the screen, pixel  
for pixel. You can drag the window to be larger (before giving the  
FRAME command), so if you have a 4000x4000-pixel screen then I  
suppose Ferret could make a 4000x4000-pixel gif.

The fundamental difference between plot metafiles and gif output is  
that the metafiles are vector graphics that *describe* the plot  
commands, whereas gif files simply save the pixels you see.

The reason that the metafile plots can be large is because they  
contain more information; information that is usually essential to  
make a fine-quality plot that can be scaled to any size. (And if you  
made a 4000x4000-pixel gif file it would be similarly large). But  
also note that gif file size scales as the number of pixels, some of  
which will be white space, so the metafile from a simple line plot  
will usually be *smaller* than the comparable gif from a large window.

You can make the final result of metafiles smaller by converting  
postscript to pdf (usually about a factor of 4 smaller, and also more  
portable).

If you really want a 300 dpi gif, several software packages can  
convert postscript or pdf to gif at whatever resolution you want.

If your metafile is really too large, typically if it has color-fills  
with very high resolution that will not be visible in a printed  
image, then perhaps you should regrid the field to lower resolution  
before doing FILL. For example, if you make a global map of a 1/10th  
degree field, the metafile will be huge and contain details that are  
useless in a printed publication. In that case regridding would be  
useful. Another simple way to reduce the metafile size in such a plot  
is to use SHADE instead of FILL: the blockiness of SHADE will not be  
visible and the file size will be smaller.

Billy K


On 10 Mar 10, at 7:26 AM, Ilias Koen wrote:

> Good morning,
>     I am a new ferret user and I am attempting to export a series  
> of publication quality graphics.
>
>     Do you know how if it's possible to output GIFs at 300dpi  
> resolution or at a pixel size that can pull publication for ex  
> 4000x4000 pixels? From our understanding the .GIF export is  
> connected to the screen resolution, or there is a maximum  
> resolution that ferret cannot export bitmap graphics above that  
> limit. We haven't found any other clear documentation on the .GIF  
> export function for ferret other than the following http:// 
> ferret.pmel.noaa.gov/Ferret/faq/controlling-the-size-of-gif-output  
> Any tips or hints on practices people have performed in the past  
> would be greatly appreciated especially for publication quality  
> graphics export.
>
> The other command option "set mode metafile" produces a PLT file  
> that is pretty large, we're wondering if there's good method to use  
> less space per image.
>
> Are there any other methods to export graphics via ferret other  
> than the two mentioned above ?
>
> Thanks Ilias Koen.