Tiff raster pictures
steve.lime at dnr.state.mn.us
Tue Mar 7 21:27:08 EST 2000
The limitation is not due to libtiff. It can handle just about any friggin tiff you give it. The limitation is purely one of GD. It can only produce 8-bit output. It's a big move to 24-bit graphics so I'm not surprised they have't done it yet although it is in the works. MapServer is poised to take advantage of it when it does happen (notice all the colors are rgb etc.).
There are some practical reasons why not to use 24-bit output. Number one is there really isn't a decent format yet. Yes, png is promising but many browsers don't support it. File sizes are another.
MapServer 8-bit output compresses well. Triple the file size (at least) and users won't be that happy. Lastly there are performance issues. Antialiased graphics, update 3+ image planes all takes time. Imagemagick supports some of the GD functionality in 24-bits but is 6 to 8 times slower. A high price to pay. JPEG simply is not well suited to line art applications.
BTW JPEG support is limited to 8-bit greyscale input. JPEG was not built to support random (ie. windowed) access so should be avoided at all cost. Use TIFF instead.
<<< <imap at chesapeake.net> 3/ 7 6:46p >>>
I think the jpeg support is currently limited to input only, but it would
be great to render 24-bit TIFFs. By the time you whack a 24-bit image
to 8-bits... It doesnt look so great anymore.
Adobe Illustrator has the ablility to zoom into a 24-bit TIFF
without pixelization or distortion of any kind. The output is
really nice.... I was hoping to see a similar functionality
is some other free graphic package like ImageMagick or GIMP.
Is it libtiff's limitation to do < 8-bit images, or what?
PNG is a output option, but JPEG would be nice too. While on the topic
of wants... Does anyone know of a public b-spline routine for multipoint
labelling? Or perhaps another algorithm that might work?
"Peter H.M. Jacobs" wrote:
> Hi all,
> does anyone know if it is poosible to render 24-bit TIF files instead of the
> 8-bit raster files?
> Is it perhaps possible with the jpeg library?
> People then have the possibility to choose between a very sharp but slow
> picture or a less sharp but faster picture.
> Peter Jacobs
Chris Stuber (mapsurfer)
Silicon Mapping Solutions, Inc.
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