Writing images of a specific size?

Submitted by chuckheron on 2008-10-23

Fraqtive is a great fractal generator! I love it!

I recently upgraded to 0.4.4 and I don't see feature that used to exist in a previous version
(I don't remember which version..)
The earlier version had a place where you could specify the size of the output image.
Does this feature still exist?
I used it to generate a full sized desktop background, and now it appears that you can only
write out an image the size of the viewing window.

I really like all the new capabilities you've added!
If this feature slipped away somehow... I'd like to request it again..

Thanks for a great program!

I was wondering this myself.

I did find a way around this. Go into full screen mode and then use ctrl+s to initiate a save. This will generate a full sized save based on your screen resolution.

Having the ability to save the fractals in a different resolution would be helpful.

Yes, this feature was present in previous versions (0.2.x and 0.3.x) and I'm planning to re-add it one day to version 0.4.x (see the roadmap). I can't tell exactly when because right now I'm more involved in WebIssues, but I'd say next year.

Also it's a very good workaround to save images in full screen mode; I've been using it as well.


I just got wise to that too. I was loading into Photofiltre and resizing the image. Not the same aspect ratio. To nearly square. I just hit the print screen key. Didn't think of Control-S :)
"How come we don't know the I.Q. of the guy who invented the test?"

That should be mentioned in the tutorial. I'll fix it in the next version (and I'll also add the possibility to generate images of arbitrary size) which will be released in a few months.



is there a way to specify a really high resolution? In the moment, the maximum seems to be 4000 pixel. I would need something like 30000 pixel for a high-resolution poster.



That's correct, the maximum size is 4000 pixel. Greater images could easily take a few gigs of memory, so the process would have to be redesigned to calculate only a part at a time. I'm so busy with my other projects at the moment, that I can't really tell if and when I will be able to return to Fraqtive.


Hey, I just changed the limits in the code, and I can easily generage 20,000 x 20,000 images.

As far as I can see, there is no reason to put such a small limit (4000) on the dimensions. At 20,000 by 20,000, I only needed about 1.6GB of memory.

I tried a 40,000 x 40,000 and it failed in creating a QImage because apparently QT images have a 4GB limit (i.e. they are limited to 32 bits I guess.). Hopefully this limit will go away in more recent version of QT.

40,000 px x 40,000 px * 4 bytes/px / 1024/1024/1024 = 5.6GB. <--- fail
20,000 px x 20,000 px * 4 bytes/px / 1024/1024/1024 = 1.5GB. <--- okay

Shoot, for some reason my code patch is causing this post to be caught by the spam filter. To fix it, simply go into the source and modify src/generateimagedialog.ui and change '4000' to '100000' or whatever you like., then recompile.

[EDIT: I just found the relavent limitation, and it's that the max Qimage dimension is 32767, so the limits should be 32767 x 32767, rather than 4000, 4000: http://stackoverflow.com/questions/7080052/qimage-qpixmap-size-limitations]

Thanks for the info. Just keep in mind that this will only work in the 64-bit version of the program. Also, in addition to the 1.5GB for the bitmap, another 3GB is needed for the temporary buffer.


Ah, interesting. I didn't see the 3GB spike when I was watching the memory usage. In any case, it's not a problem on a modern 64-bit computer with 8 GB of ram. It only takes a few minutes to compute on my 4 year old Macbook pro with a core-2 duo at 2GHZ with 8GB ram and I can get fantastic high resolution images.


Would it be possible to make this very simple change to the Windows x64 Windows Installer version to allow 32767 width and height? Perhaps a minor point revision ( to the project? Rendering at a higher resolution and downsizing the resultant images can give a higher resolution result (greater detail) than directly rendering in the desired resolution. I can provide a tutorial on how to make a very high quality video, but the default maximum 4000 pixel width and heights limiting the quality possible. You can see this by rendering at 4000x4000 and resizing to 500x500. Compare this to rendering at 2000x2000 and resizing to 500x500, 1000x1000 and resizing, and rendering at 500x500. I have been using paint.net using the default fant downsizing and the quality difference is highest from starting a 8x larger image and resizing. I tried resizing to 250x250 to test if there was a quality difference comparing 8x to 16x, but the difference was nearly imperceptible. It appears the highest quality is by rendering 8x larger and resizing using WIC fant for resizing.