PS - How to resize a PNG without distorting?

Discussion in 'Design and Graphics' started by bluetooth, May 21, 2007.

  1. bluetooth macrumors 6502a

    bluetooth

    Joined:
    May 1, 2007
    Location:
    Toronto
    #1
    Ok, so I took a snap of my MAC desktop. The image is automatically converted to a PNG file.

    I open this file in photoshop, looks great (resolution and all).

    I try to resize to a smaller size and I loose clarity and resolution and yes, I am trying to scale down, not up.

    I have tried a few things, flattening image as .eps - adding a vector mask. Nothing has worked.

    It is probably obvious, but what am I doing or not doing here? How can you take a desktop image PNG file and scale it down without altering/sacrificing the quality/clarity etc.?

    thanks!
     
  2. TheAnswer macrumors 68030

    TheAnswer

    Joined:
    Jan 25, 2002
    Location:
    Orange County, CA
    #2
    You know that Preview has a built in scale tool right? (You might have to go to View>Customize Toolbar to reveal it, though).
     
  3. iBookG4user macrumors 604

    iBookG4user

    Joined:
    Jun 27, 2006
    Location:
    Seattle, WA
    #3
    I'm not an expert on this by any means, but I've heard that if you reduce the image's resolution by half each time, it will maintain a higher quality. an example being if the image is 1440 x 900, then resize it to 720 x 450 and so on and so forth. You could try that to see if that works better.
     
  4. Super Macho Man macrumors 6502a

    Super Macho Man

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    Jul 24, 2006
    Location:
    Hollywood, CA
    #4
    It loses clarity and resolution because it loses clarity and resolution... that's what resizing to a lower resolution does, it reduces resolution, by throwing out large numbers of pixels and representing the image with fewer numbers of pixels. Resize a 1440x900 image to 320xwhatever and zoom in so that the 320 file is the same size (screen area) as the 1440 was, and you'll see clearly what just happened...
     
  5. Nermal Moderator

    Nermal

    Staff Member

    Joined:
    Dec 7, 2002
    Location:
    New Zealand
    #5
    I'm certainly not a "graphics guy" but I've found that Fireworks performs much better resizing than Photoshop. It therefore follows that Photoshop isn't the best, so try out Preview and see how well it does it.

    Edit: I don't see how to resize using Preview. I'm pretty sure I remember doing it in Jaguar, but Tiger's version only appears to "zoom" and doesn't seem to save the changes.
     
  6. ATD macrumors 6502a

    Joined:
    Sep 25, 2005
    #6
    It's easy, any transformation you do to a raster file will bring down the quality. Sizing up or down, rotating, skew, distort, wrap, perspective. The only exceptions are rotations at 90, -90 & 180 degrees and flips. Also clean math will hold up better than odd numbers (as iBookG4user suggested). For example a file reduced to exactly 50% might be shaper than one reduced to 63.5429%. The reason is the pixel divisions, when a pixel divided in half the edges don't shift, it's just split in 2. In the case of 50%, exactly 2 pixels become one (it's actually 4 becoming 1). If you do an odd size like 63.5429% each pixel is divided by .635429, all the edges shift causing the detail to shift. The result is the file gets softer. If you do transformation after transformation it just gets softer and softer.
     
  7. TheAnswer macrumors 68030

    TheAnswer

    Joined:
    Jan 25, 2002
    Location:
    Orange County, CA
    #7
    Looks like you are right...strange that the Automator action to scale using Preview works and saves the changes perfectly, but I can't seem to use the scale tool in Preview (from View > Customize Toolbar) and get Preview to save it...even if I choose Save As. I can't see why the Automator action would work and not the app itself...strange!
     
  8. decksnap macrumors 68040

    decksnap

    Joined:
    Apr 11, 2003
    #8
    What are you trying to do with it? You could change the 'dimensions' and keep the clarity by upping the dpi and keeping the pixel count the same. This changes the dimensions in inches for print use, but does nothing for on-screen applciations.
     
  9. Stratification macrumors regular

    Joined:
    Jan 17, 2005
    Location:
    Spokane, WA
    #9
    Make sure you're using Bicubic Sharper to resize. I usually then (if I'm in a hurry) just do an Unsharp Mask filter on it somewhere from 30% to 50% depending on what looks good.
     
  10. The Past macrumors 6502

    Joined:
    Aug 17, 2004
    #10
  11. bluetooth thread starter macrumors 6502a

    bluetooth

    Joined:
    May 1, 2007
    Location:
    Toronto
    #11
    Ok greatm I will give some of the above a try - thanks guys.
     

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