transparency on jpegs

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transparency on jpegs

Postby ttrw » Wed Mar 19, 2008 1:20 am

When importing a jpeg to draw around, or place in the background, it would be really useful if QCad could do this!! Guys?
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Postby andrew » Wed Mar 19, 2008 9:45 am

Please note that the JPEG format does not support transparency.

You might want to use PNG instead. PNG supports transparency and QCad takes that into account when importing a PNG. Please refer also to the example swiss_map.dxf which comes with every QCad package.
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Postby ttrw » Wed Mar 19, 2008 10:10 am

andrew wrote:Please note that the JPEG format does not support transparency.


Maybe not with Windows (?), but jpeg's most certainly do support transparency in Mac OS X!

Anyway, thanks for the advice. I'll try a PNG- FWIW I'm using PNG files more and more these days- as opposed to jpegs- maybe that is another 'windows thing'? :roll:
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Postby andrew » Wed Mar 19, 2008 10:21 am

JPEG as a file format does not support transparency. That means the format is specified that way. This has nothing to do with the operating system. However, some applications might choose to fake a transparency effect by using a certain color(-range) for the transparent part.

PNG is certainly the way to go and by no means a Windows thing.

See http://en.wikipedia.org/wiki/Portable_Network_Graphics for some interesting details about PNG. There's also a comparison to JPEG.
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Postby ttrw » Wed Mar 19, 2008 10:34 am

:lol:

Sorry Andrew, you're absolutely right! :lol:

Too much coffee and not enough breakfast! :D

Is it possible then to request a png transparency 'slider' at some point in the not too distant future?
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Postby andrew » Wed Mar 19, 2008 10:51 am

ttrw wrote:Is it possible then to request a png transparency 'slider' at some point in the not too distant future?


The transparency of PNGs is handled inside the PNG file. So you would have to adjust the transparency of the PNG directly with an image manipulation program such as the GIMP (free) or PhotoShop. QCad itself cannot do any bitmap manipulations or effects. This will probably not change anytime soon since bitmap manipulation programs are of course much better at these things than QCad would ever be.
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Postby ttrw » Wed Mar 19, 2008 8:41 pm

Yes, I suppose that's one of the wonders of an application written in Cocoa rather than the Trolltech framework- ie you can apply transparency to a png via the Quartz graphics, like one can do in many cocoa native apps- but alas then not QCad? Shame.

Would Trolltech add this if you asked them nicely enough?
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Postby andrew » Wed Mar 19, 2008 10:28 pm

Of course that's also possible with Qt. The question is whether QCad should do that or if that is rather the task of a image manipulation program. How would you define in QCad which areas are transparent? There is no way to make pixel based selections, etc.
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Postby ttrw » Wed Mar 19, 2008 10:57 pm

Areas that are transparent? By setting a layer specifically for an imported image?

One thing I know is very much on the increase right now, and you guys should look into it IMVHO, is GIS (or Geographic Information Systems);

http://www.gis.com/whatisgis/index.html

http://en.wikipedia.org/wiki/Geographic ... ion_system

The ability to trace from maps and satellite images from say Google Earth, could easily be manipulated and traced within QCad and exported to say Google SketchUp to make a 3D representation. I put some stuff about importing from QCad into SketchUp here;

http://www.ribbonsoft.com/rsforum/viewtopic.php?t=321

GIS is used by architects and planners to map areas which are to be made ready for development. Currently GIS applications exist for Windows (ArchGIS springs to mind), but there are few available for Linux or Mac OS X. Most GIS systems works in a very similar manner to AutoCAD and they also export DXF's.
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Postby andrew » Thu Mar 20, 2008 11:20 am

Thanks for the input. I am aware of GIS (my dissertation was on a GIS related topic).

We might add transparency as an attribute (like color, layer, line width, ...) to all entities at one point.

How about putting the bitmap(s) in the background of your drawing for now? Please let me know if that does not solve the problem and why exactly.
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Postby ttrw » Thu Mar 20, 2008 11:42 am

andrew wrote:We might add transparency as an attribute (like color, layer, line width, ...) to all entities at one point.


Ahh sweet music to my ears! :D

andrew wrote:How about putting the bitmap(s) in the background of your drawing for now? Please let me know if that does not solve the problem and why exactly.


Yes, I'll let you know of course, how I get on. Right now, I too am doing my dissertation! But, fwiw, I did try to put a bitmap in the background- but it was fiddly. However, to be honest, it's about the only thing in QCad that IS fiddly- and that's a plus in my book 8)
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Postby stan.distortion » Fri Apr 04, 2008 1:23 pm

I'll throw in my 2c for transparent entities, especially fills. It would be very usefull here. Logged in with a couple of suggestions and another one kind of fits in here, configuring entities to be above or below others. That's kind of heading towards the big '3d' question though so I'll start another thread if one doesn't exist already.
Cheers.
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Re: I'm not a subject, I'm a free man....hahahah

Postby andrew » Fri Apr 04, 2008 1:27 pm

stan.distortion wrote:configuring entities to be above or below others


Please have a look at "Modify" - "Bring to Front" and "Modify" - "Send to Back"
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Postby stan.distortion » Fri Apr 04, 2008 1:37 pm

Cheers for the blindingly fast reply :) Feeling very stupid now, not reading the manual is one thing but not even checking whats in the menus is unforgivable.
Thanks
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