Frequently Asked Questions

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  • Tutorials

    Here are some external tutorials and instructions on how to use Rasterbator.

  • The output is nothing but dots!

    Yes, that is the idea. Rasterbator generates posters, even giant ones, from relatively low-resolution images, by converting them to dots. There is probably some kind of illusion at play here, as when you look the posters from far away, they look surprisingly sharp and detailed. Maybe the brain fills in missing information to the visual perception, or something like that.

    If you just want to blow up (and pixelate) your image without any of that sorcery messing up your perception, you can select a less wild output mode in Phase 4 when creating your poster.

  • Isn't it actually half-toning instead of rasterizing?

    Yes, the technical process is called half-toning (widely used, but almost always with much smaller dot size), but Halftonizer would have been just non-imaginative. And, well, rasters are at least somewhat related.

  • I want to suggest a feature!

    Great! Please use the feature forum. You can also upvote ideas other people have sent.

  • It doesn't work.

    Please use a browser that is relatively new (no more than 2 years old). You actually should use the latest version anyway just for security reasons. It works best with Chrome.

    Sorry for not supporting old browsers. From the viewpoint of web development, it is quite a luxury to not have the commercial imperatives to do that.

  • Uploading takes a long time!

    Upload time depends on the file size and your network connection and in worst cases the upload may take tens of minutes. If you use the drag and drop feature, Rasterbator will display the process in percentage. If it takes intolerably long, try to make a smaller version of the image with some image editing application.

    If for some reason the upload just doesn't work (even with small files), this can be worked around by uploading the image to some hosting service such as and then using the URL to load the image for rasterbation.

  • What about the privacy of my images?

    The images that are uploaded and created (rasterbation pdf and preview images) are saved to a temporary storage for about 4 hours. A cleanup process that runs every 15 minutes deletes them automatically after that time.

    Some information is saved to log files: unique identifier that is basically a random code (embedded to the PDF metadata also, that is useful for tracking bugs), the original image size, file size and parameters such as colors and file size etc. The image content, original filename or any non-technical image metadata are not saved.

    And despite of all the good intentions, Rasterbator runs in Microsoft Azure and it is quite likely that NSA has access to all the data anyway. So don't rasterbate any state secrets.

  • Is there an app available?

    Unfortunately no. And there are no plans to make a Rasterbator app at the moment. But the web site should work pretty well with most common tablets and phones.

    For Apple devices, a good alternative is the Raster app. (No connection to this site except friendly correspondence between developers.)

  • What print settings to use?

    Use the paper size you selected for rasterbating. For sizing options, use Actual size or similar option. This is how to do it in Acrobat Reader X for Windows.

    If you didn't use margin and want to use as much paper area as your printer can print to, use Fit to page instead.

  • The assembled poster is a bit smaller than expected.

    This may happen due to printer margins. Different printers have non-printable areas that are of different size. Rasterbator is not aware of what are the margins of the printer that will be used to print the output. It generates the output always onto full pages and the PDF reader does the scaling down to printable area. For example, if the page is A4, with width of 210mm and printer cannot print to a 2mm stripe on each side, this will create an error of 1,9%.

    If you know the exact printable area of your printer (it can be found out using Word ) please select Custom paper size in Rasterbator phase 2 and use the printable area as the paper size. The result will be more accurately sized posters.

  • How do the page position markers work?

    They are the coordinates of each page in the poster. The notation is similar to which is used to refer to cells in everyone's favorite software, Microsoft Excel! Letters mark the column so that they go from A to Z, which is followed by AA and AB. After AZ comes BA, BB and BC and so on. Numbers mark the rows. For example, the paper marked with D7 goes to the fourth column and seventh row.

    Assemble the poster like this:

    A1B1C1...D to X here...Z1AA1AB1...

    Position marker may overlap rasterbated area depending on dot and page size. It is about 2mm high.

  • Is Rasterbator free to use for commercial purposes?


    I'd appreciate if you tweeted or sent a message about how you used it and included credits if applicable, but they are absolutely not necessary. Note that the peppy "Yes!" applies only to the image processing that Rasterbator does. Especially commercial use may require a license from the source image copyright holder. This depends on a huge amount of different variables (country of origin, country of use, time of publication of the original, does the original meet threshold of originality etc.) and can be a very messy subject, so if you are unsure and use the poster commercially, I suggest lawyering up.

  • The standalone version came with adware or other crap!

    The standalone version is available from many freeware sites. Unfortunately, some of these try to coax you to download the application using their own installer program that also installs browser toolbars, adware or something else you didn't actually want.

    Rasterbator Standalone by itself does nothing but rasterbates. Download it here.

  • What do margin and overlap mean?

    Most printers cannot print to the entire page area and hence margins are needed. If you know the margins for your printer, enter their width. The default, 10mm, is a safe bet and should work with practically all printers.

    Overlap (or bleed) makes it easier to cut away the margins. The image overlaps at the edges of adjoining sheets. This means the cut does not need to be very precise, it will be sufficient if the path of the cut just goes along the overlap area (though straight cuts may look better). Note that the overlap is placed in the margin area, in other words, adding overlap does not effect the poster size.

  • What are crop marks?

    Crop marks are lines in the corners of the papers that show how to cut away the margins.

    If you do not add a margin, the crop marks cannot be displayed (as there just is not any room for them).

    Note that if you select the Overlap option, the crop marks are positioned at the non-overlapped part of the image, and cutting by them will actually seem like you are cutting away part of the image (but it is duplicate of the part of the next page inside the crop marks).

  • How can utilize the entire page so there are no partially printed pages at right column or bottom row?

    To utilize full pages, the aspect ratio (width divided by height) must be the same in the source image than in the output.

    For example, if you intend to print to A4, the paper size is 210x297 mm. With 10 mm margin at each side, the printable area is 190x277 mm. Hence, the aspect ratio is 190/277=0.686.

    If you have an image that is 1200 pixels wide, you can calculate the height that utilizes entire page by dividing it with the aspect ratio. 1200/0.686=1749.2, so you should crop the image to 1200x1749. Round down to avoid pages with only a narrow line of image content.

    You can also calculate the image size based on height.

  • What does the Raster size option do?

    It allows you to set the minimum and maximum dot size and this way control the "tone" of the output. The raster size is set relative to grid size (how far apart the dots are from each other, measured in millimeters).

    A raster size range of 0-100% means that completely white areas in source image yield no dots to the output. Completely black areas produce dots so large they fill the entire area with the output color.

    If you want to have blank space between all the dots, select maximum value of around 70%. If you want the original image to barely appear, select something like 40-60%.

    Source image
    Raster size 0-100%
    Raster size 0-70%
    Raster size 30-70%

    Note that in halftone rasterbation raster size is calculated diagonally, since circles are being placed inside squares and they must overlap to fill areas completely. So with max 100% raster size the max raster diameter is √(Grid size2 + Grid size2) ≈ 1.41 * Grid size .