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dpi for print.

Bea Heard
2011-10-15
2013-04-15
  • Bea Heard
    Bea Heard
    2011-10-15

    first thanks so much for a great contribution…Very impressed all round.  The one thing I need and wonder if you could provide direction or possbily price to complete.
    Printing.  it is not so much the size of the file or output we need to print but the dpi which on the version I downloaded outputs to 75 dpi - in hard print world, this will never reproduce no matter what size the output file is.It is perfect for screen.
    For printing we need 300dpi output - Hoping you can assist.
    thanks again.

     
  • Paul Gentieu
    Paul Gentieu
    2011-10-18

    Hi, I'm not sure I totally understand your question, but there isn't a concept of dpi in Quickman. It just creates pixels. So if you have, say, a 10x10" image on your screen, and the screen is 75dpi, then the image dimensions are 750 x 750 (the actual dimensions are shown on the Size line at the top right of the window). To create the same image at 300dpi, you would multiply each dimension by 4, save the image, then print it at the same 10x10" size.

    To do that, enter 3000 x 3000 (or whatever the current x and y dimensions are, multiplied by 4) in the size box above the Save Image button, and click the button. That creates the same image you see on the screen but with more pixels. If you now print this file at 10x10" on the printer, it will be 300dpi.

    If you're actually looking to make a smoother picture, that's tricky with Mandelbrot images as they don't get any less detailed no matter how much resolution you use. One way is to save the image at an even larger size (say another 4x over the 300dpi dimensions), then downscale it in an image editor to the print dimensions. That  will average out the fine detail and make the image look smoother.

    Hope this helps…

     
  • Paul Gentieu
    Paul Gentieu
    2011-10-18

    I noticed there seems to be a dpi field in the PNG images Quickman saves. On my system it shows up as 96 dpi. That's just a default though. If your image editor is using this value, just override it with 300 dpi, or tell the editor to print at the desired size. It's really the image dimensions and selected print size that determine the actual dpi.

     
  • Bea Heard
    Bea Heard
    2011-12-02

    Apologies  was  expecting response andmust have missed it altogether.  Thanks so much for the followup. I had trialled all those options and do get larger files (70000x70000) however is increases the size but not in relation to  pixels per inch.  So becasue it does not constrain the area it is generating larger pictures but with the same DotPerInch ratio..   Wish I could show you what I mean with an attachment.

     
  • Paul Gentieu
    Paul Gentieu
    2011-12-10

    You could upload your images to a website like flickr, then post a link to them here…

     
  • Bea Heard
    Bea Heard
    2011-12-10

    Thansk for that - we use for large format printing -  our prints are  anywhere from 1mt or 3 foot square.  Screen graphics is not a concern to us.  Thanks anyways was just hoping someone could do something with the output for this purpose.

    Kind regards
    Bea

     
  • Paul Gentieu
    Paul Gentieu
    2011-12-10

    A 3 x 3 foot image at 300 dpi would be 10800 x 10800. You could try generating the image at 4x resolution (43200 x 43200), then load it into Photoshop and use some of its tools to smooth it. The noise reduction, dust and scratch, and/or blur filters would probably work well since the fine details (which you don't want) are basically noise.

    After smoothing, resize the image back to 10800 x 10800 and print it.

     
  • Paul Gentieu
    Paul Gentieu
    2011-12-10

    One other tip: it's best to stay at low zoom levels when making very large images, to avoid precision loss. Maybe this is what you're seeing. When precision loss happens the "pixels" get larger and become oddly shaped, and the image gets generally mangled. One day I might try to add arbitrary precision support to Quickman, but that's a big project…

     
  • Bea Heard
    Bea Heard
    2011-12-10

    Yes that is what we see the jagged pixels when we want a large print -  If ever you do embark on that project please let us know… Very apreciated all round - thanks again

     
  • Paul Gentieu
    Paul Gentieu
    2011-12-10

    Ok, so it's precision loss. If you can find some good images at low zoom (magnification) levels, they should look much better. The "Mag" number in the upper right corner of the window shows the magnification. The second image in the Quickman.log file has a low Mag of 2835, which should be fine at almost any size.

    The threshold for quality loss will vary (depends on the output size, and where the image is), but anything above a few million or so might start to have issues. (I just tried one with a Mag of 12 million at 10,000 x 10000, and it looked fine).