Image manipulation in a console program

mdp · Post by **mdp** » Tue Sep 16, 2008 9:11 pm

I am coding a PB cgi that works on a x-less webserver, but internally uses image manipulation functions. It's a small GIS, to give the idea.

Having

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UseJPEGImageDecoder() : LoadImage(#myImage,"myEarthImage.jpg")

inside, produces:

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Gtk-WARNING **: cannot open display

The program stops there.

The GTK libraries are in place, only thing I'm not running is a X server.
I supposed image operation in a console only environment should be possible...

Can you help?

Trond · Post by **Trond** » Wed Sep 17, 2008 8:18 pm

It is only a warning, it shouldn't create further problems.

mdp · Post by **mdp** » Wed Sep 17, 2008 9:53 pm

Trond, try some

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OpenConsole()
UseJPEGImageDecoder()
PrintN("Will you see this?")

Sorry I'm not testing the above code right now (I just finished the GIS via javascript only - a language I love so much I just restarted smoking), but the concept is akin to the one tested yesterday. The program "stopped".
You will not see the output... Do you confirm?

mdp · Post by **mdp** » Thu Sep 18, 2008 1:31 pm

...I tried now.
The above code will actually work (sorry), but:

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OpenConsole()
UseJPEGImageDecoder()
CreateImage(0,100,100)
PrintN("Will you see this?")

Will not work, CreateImage() will cause the CannotOpenDisplay error.
On an abstract (non technical) evaluation that should be legitimate (I can operate on images for saving them, output them through MIME etc.). Is there anything I am missing?

El_Choni · Post by **El_Choni** » Wed Apr 15, 2009 5:39 pm

I have the same problem with LoadImage (PB Linux 4.30, Linux executable, CentOS 5.0 AMD 64): "Gtk-WARNING **: cannot open display"

Post by **freak** » Wed Apr 15, 2009 5:48 pm

There is no way around this in PB 4.30. PB Images are GdkPixmap objects which are actually managed by the X server, so without one you cannot create an image. 4.40 will use GdkPixbuf which is actually a client-side memory buffer. I am not sure though wether you can do without an X server then or not.

El_Choni · Post by **El_Choni** » Wed Apr 15, 2009 5:57 pm

Thanks, Freak.

(Now I'll try to find what an X server is and wether I have it or not; I'm new to Linux)

walker · Post by **walker** » Wed Apr 15, 2009 7:15 pm

El_Choni wrote:Thanks, Freak.

(Now I'll try to find what an X server is and wether I have it or not; I'm new to Linux)

if you have a graphical environment (gnome, kde etc) you have an X-Server running ...

El_Choni · Post by **El_Choni** » Thu Apr 16, 2009 9:52 am

Ok, no X server. Apparently my server is running in a virtual box called Virtuozzo which won't even show me the name of a virtual graphic card.

My app needs to do mainly these tasks:

1. Download images from a remote web site.
2. Load those images.
3. Manipulate those images.
4. Upload manipulated images to a client.

My app doesn't actually need to render or show the images. So now I'll try to use libjpeg and libpng in order to be able to load images, manipulate them directly in memory and save them after.

Thanks for your help.

DarkDragon · Post by **DarkDragon** » Thu Apr 16, 2009 10:53 am

Try using Xvnc. I do so for some wine applications. But on servers you'd better have a firewall and block the port whenever you don't use it (You maybe also use it through vpn). And always use a password!

El_Choni · Post by **El_Choni** » Thu Apr 16, 2009 11:13 am

Thanks, but I'm afraid my host provider won't give me that option.

bembulak · Post by **bembulak** » Fri Apr 17, 2009 8:24 am

Optionally you could try to call "ImageMagick" via RunProgram, if it's installed, or any other external libs.

El_Choni · Post by **El_Choni** » Fri Apr 17, 2009 1:44 pm

Thank you, I'll try -I had given up libjpeg and was trying using Gdk directly.