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  1. #1
    Super Moderator BATcher's Avatar
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    'Image size' simple rule-of-thumb

    I wish to resample/resize a large graphic image (logo, actually) so that when printed, or viewed on a screen, it is as close as possible to 5 cm wide (or, if it makes the maths easier, 2 inches wide!).

    To what number should I set the width of the image in pixels to get the above figures? I am getting conflicting results in the variety of graphics programs and viewers I've tried.

    Will one image size work for both printing and viewing?

    Thanks!
    BATcher

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    Plutonium Lounger Leif's Avatar
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    Re: 'Image size' simple rule-of-thumb

    I would guess that it would depend entirely on the DPI / resolution setting of your monitor...

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    Super Moderator BATcher's Avatar
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    Re: 'Image size' simple rule-of-thumb

    True indeed - some quick calculations for 15" (1024 x 768) screens to 20.1" (1600 x 1200) screens (not wide-screen) give horizontal pixel counts of between 76 and 100 per horizontal inch, assuming the natural resolution is chosen (for LCD screens).

    Is there a 'magic number' for printers, then, or does the same sort of variation apply? I always thought it used to come out at 300 DPI, which foolishly I equate with pixels per inch...
    BATcher

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    Plutonium Lounger Leif's Avatar
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    Re: 'Image size' simple rule-of-thumb

    Dunno, as they say, but using Microsoft Photo Editor, there does seem to be something to infer what size a picture will be.....

    (And yes, I did try printing it and it did come out that size <img src=/S/grin.gif border=0 alt=grin width=15 height=15> )
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    Super Moderator jscher2000's Avatar
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    Re: 'Image size' simple rule-of-thumb

    Browsers print at 96 pixels per inch. I think this also is a reasonable figure for the average monitor. It will be a little small on high density monitors, but so is everything else, so your image won't be disproportionately small. <img src=/S/smile.gif border=0 alt=smile width=15 height=15>


    (You might be able to stretch the image using a script when your page encounters a higher density monitor. I wrote a script for this once, but I don't have the code handy. The general concept was to use point measurements, since you know there are 72 points per inch. Actually, I don't remember whether it worked!!)

  6. #6
    Super Moderator BATcher's Avatar
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    Re: 'Image size' simple rule-of-thumb

    Thanks, Jefferson - I'm not really worried about it being the exact size - I was (originally) after a rule which would enable me to resize an image which would end up displaying and printing at (about) 3 cm wide.

    Having played with an image we were provided with which had "150 DPI" in its filename, I displayed it in MS PhotoEditor, examined the Properties, and printed it and found that, yes, it came out at 150 dots per inch!
    BATcher

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    [quote name='BATcher' post='751440' date='07-Jan-09 08:19']Thanks, Jefferson - I'm not really worried about it being the exact size - I was (originally) after a rule which would enable me to resize an image which would end up displaying and printing at (about) 3 cm wide.

    Having played with an image we were provided with which had "150 DPI" in its filename, I displayed it in MS PhotoEditor, examined the Properties, and printed it and found that, yes, it came out at 150 dots per inch![/quote]
    Hi Batcher,

    There is no single set of image dimensions you can use to achieve the same size output on screen and in print. Simply because there are too many variables involved. Screen resolutions typically run from 96-120 ppi, whilst printer densities are typically multiples of 300 or 360 dpi. Any image can be displayed at whatever ppi you choose for screen work and printed with a completely different dpi setting.

    It all comes down to how you set the display/print parameters. If you're going to print an image, work out what you need for that and downscale for screen display purposes. Doing the reverse typically results in pixelated prints.
    Cheers,

    Paul Edstein
    [MS MVP - Word]

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    Super Moderator jscher2000's Avatar
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    I've subsequently been shown that you can improve print output by specifying a higher resolution image but constraining it to smaller dimensions. For example, if you create an <img> tag that pulls in an image that is 600x600, but you set the height and width to 400, the print output will take advantage of the extra pixels (the screen cannot).

    This thread has the details: High-res images for print version @ mozillaZine Forums.

  9. #9
    Uranium Lounger
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    [quote name='BATcher' post='751211' date='05-Jan-09 16:07']True indeed - some quick calculations for 15" (1024 x 768) screens to 20.1" (1600 x 1200) screens (not wide-screen) give horizontal pixel counts of between 76 and 100 per horizontal inch, assuming the natural resolution is chosen (for LCD screens).

    Is there a 'magic number' for printers, then, or does the same sort of variation apply? I always thought it used to come out at 300 DPI, which foolishly I equate with pixels per inch...[/quote]

    According to Canon, you are not so foolish.
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