View Full Version : rasterizing to blow up?

Jul 13, 2006, 07:50 AM
i have this image i would like to blow up into a poster as a gift, but the resolution of it is very poor and i know if i blew it up it would be pixilated and ugly. is there a way to rasterize an image (i don't think this is the correct term) so that when i blow it up instead of it being all pixel-y it's all circle-y?

Jul 13, 2006, 08:54 AM
Not sure how much you want to enlarge your image, but you could try the rasterbator (http://homokaasu.org/rasterbator/) (great name). I don't have the site handy, but you could easily find it with a google search. It allows you to rasterize any image and enlarge it to any size from about 3 ft by 5 ft up to larger than any surface you could possibly have to display on. The image is sent back as a pdf that you print across multiple pages. The quality is remarkable if you stand far enough away.

edit : found website, I think it's also available as a download.

Jul 13, 2006, 09:31 AM
Another thread: http://forums.macrumors.com/showthread.php?t=216272 :p

Jul 13, 2006, 02:24 PM
ah that's what it's called: rasterbation. thanks. that forum link isn't valid, but i'll do a search. i also hope there's a mac app that can do this.

Jul 13, 2006, 02:31 PM
yeah the online app is too restricting. I want one large page and i want smaller dots. does that GIMP app or photoshop have similar capabilities. I don't really want the whole rasterbated effect just the not pixel-y blow up.

Jul 13, 2006, 03:45 PM

Raster graphics cannot be scaled to a higher resolution without loss of apparent quality. This is in contrast to vector graphics, which easily scale to the quality of the device on which they are rendered. Raster graphics are more practical than vector graphics for photographs and photo-realistic images, while vector graphics are often more practical for typesetting or graphic design. Modern computer monitors typically display about 72 to 130 pixels per inch (PPI), and some modern consumer printers can resolve 2400 dots per inch (DPI) or more; determining the most appropriate image resolution for a given printer resolution can be difficult, since printed output may have a greater level of detail than can be discerned on a monitor.

Jul 13, 2006, 05:48 PM

Jul 13, 2006, 08:46 PM

Thanks for saying it so I didn't have to.

Did anybody try using it yet? I simply don't believe that it works well. This part in particular sounds bogus to me:

After you have set the options and the rasterbation begins, you may end up in a queue. Rasterbation uses a lot of memory, hence this conserves server resources and actually reduces the average time users have to wait. When your turn begins, the server examines the original image (preview image is not used here to ensure maximum quality). The image is divided into squares. Each square maps to a dot in the output. The average brightness and color values of the origin square determine the size (and color if desired) of the output dot - bright area produces a small dot. Vector representations of the dots are written into a pdf document. When the entire image is processed, your browser is sent to a different page, which will instruct it to download the pdf file.

Maybe I'll send something in and see what I get back. It just sounds like their algorithm is way too simplistic to blow something up thousands of times its original size...vectorization involves complex calculus and/or fractal geometry, not some goofus making a grainy mural of the pope.

Jul 13, 2006, 09:16 PM
It's certainly not a high quality product that you get back from the rasterbator site. Nothing even approaching photo quality - more like what you would see in a black and white photo in a newspaper, only much larger. I've made images that measured about 5 by 7 feet, and were easily recognizable from about 40 feet away. People's faces could be identified, as well as major features of the original image, but not any fine details.

Be aware that printing these files takes huge amounts of ink/toner. You're basically printing 25 or more pages that probably average 50% coverage or so. I usually did them at work on a laser printer, and had to print in 7 or 8 page chunks so the printer didn't overheat and leave streaks.

Mac Kiwi
Jul 15, 2006, 05:20 AM
Photoshop CS2 has upsample abilities which are not to bad.Open your image in CS2 and instead of using bicubic change it to bicubic smoother for upsample and sharper for downsample.It might come out ok depending on how much you want to upsample.There are also smart objects in CS2,mind you the result will be the same with a smart object is my guess.