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How-To: Scale Photos and Images with GIMP

Discussion in 'FAQ and Suggestions' started by GPS, Mar 30, 2013.

  1. GPS

    GPS Registered

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    I've been wanting to make a post about photo sizing and re-sizing for a while...let's do this.

    I am going to be using GIMP (GNU Image Manipulation Program) for this how-to.

    Why GIMP?
    GIMP is free open source software and is available for all the popular operating systems: Linux, Apple OS X and Microsoft Windows.  You can download GIMP for your operating system from the GIMP website here: http://www.gimp.org/
    GIMP is almost as powerful as Adobe Photoshop, but like I mentioned it is free, not $600 so that's a big win.  Like Photoshop, GIMP can be a little intimidating if you've never used a professional photo manipulation program before.  We'll focus on resizing a sample photo for it's dimensions and storage space requirements.

    Overview:
    Although we will break this how-to down to the details there are only three steps to scale a photo and reduce it's volume in GIMP.
    They are:

    - Open the photo you want to scale.
    - Scale it.
    - Export the photo setting the quality to reduce the hard disk volume.

    That's all.

    Step by Step
    Now let's do it in step by step detail.

    1.  Get GIMP and install it on your computer from here:  http://www.gimp.org/downloads/

    2.  Start GIMP
    On my computer I see the GIMP icon in my dock like this:

    [​IMG]

    3.  When GIMP is open you should see a screen similar to this:

    [​IMG]

    4.  Open a photo to manipulate like this: File menu | Open - then find the photo you want to manipulate.

    [​IMG]

    I've chosen a photo of my Axial AX10 with Novak brushless system.  This is what is on my screen now:

    [​IMG]

    The photo I have selected is 2560 pixels wide by 1920 pixels high (2560x1920) and is therefore way too big for the website.  Uploading a photo this big will force people viewing it to have to scroll left and right so they won't be able to see the whole photo at once.
    A good size that fits all at once on most peoples PC, and many mobile devices, is 800 pixels wide by 600 high (800x600) so that's the size we will change this photo to.

    5.  Scale the photo to 800x600.  This is very easy with GIMP by clicking the "Scale Tool" here:

    [​IMG]

    6.  Now click anywhere on your photo.  The Scale Tool dialog box opens:

    [​IMG]

    7.  We want to maintain the aspect ratio of the photo so it doesn't get tall and thin or short and fat.  To have GIMP do that automatically we want to click the "Chain" which locks the aspect ratios like this:

    [​IMG]

    8.  Now let's set the width to 800.  Enter 800 in the width box then press the TAB key on your keyboard or click the mouse in the Height box.  The height changes automatically.  In my case 600, your size may differ if you started with a photo with a different size than my 2560x1920 sample.

    [​IMG]

    9.  Clicking the "Scale" button closes the dialog box and changes the photo's size.  Now you should see something like this:

    [​IMG]

    What we have now is a scaled photo but the "Canvas" is still the original size (2560x1920).  If you stop here you will have a reduced photo on a huge background.  We need to reduce the overall canvas now and GIMP has a super easy way to do this.

    10.  From the Image menu select "Fit Canvas to Layers".

    [​IMG]

    Bam!  Now you see this:

    [​IMG]

    We are almost there.  We have reduced the photo and the canvas dimensions so the only step is to reduce the storage size, the Kilobytes or Megabytes which is the space on the hard drive that the photo occupies.  We do this by exporting the photo to a compressible format like JPEG (JPG).  Let's go.

    11.  Click the File menu, then "Export".

    [​IMG]

    You will get this:

    [​IMG]

    Click on "Select File Type (by extension)" to open a additional area at the bottom of the dialog box.  And we will choose JPEG like in this photo:

    [​IMG]

    Now you get another dialog box called "Export Image as JPEG" that looks like this:

    [​IMG]

    This Export Image as JPEG dialog box allows up to reduce the size that the photo occupies on the hard drive by reducing the quality slightly.  I've found that setting the quality to 80% gets a good reduction in the size yet maintains a great looking photo.  Feel free to experiment with this setting on your photos and see what you find.

    [​IMG]

    After setting the quality click the "Export" button.

    Here are the results:

    [​IMG]

    This photo was reduced from 2560 pixels wide and 1920 pixels high to 800 pixels wide and 600 high.  The space requirements for the original file were a little over 1 Megabyte and the exported JPEG file is now 106 Kilobytes, almost one tenth the size of the original.

    I hope you find this how-to useful.  It may look like a lot of steps, but they are very simple and you will be able to fly through them after you do it a couple times.  If you have any questions on this let me know.
  2. w00d

    w00d Registered

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    Excuse my ignorance Yoda, but the image you are working from is that yours?
    ... Only reason I ask, if indeed your image I must say it's marked improvement (and to say less kindly) over some of your other grab and post shots.
    ... haha, maybe you was paying attention in class ...

    Seems to me you but some extra effort into this shot that worked well in your favor  [​IMG] [​IMG] [​IMG]
  3. GPS

    GPS Registered

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    I don't understand.  Are you referring to the Axial AX10 crawler photo or the screen grabs of Gimp?  I haven't done anything different than with any other photos I've posted.
  4. w00d

    w00d Registered

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    LOL, I'm saying I like the photo of the Axial AX10 [​IMG]
  5. Nexus

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    For what it's worth - you can save yourselves a couple of steps if you aren't interested in keeping the original, full-resolution image.

    When you're ready to save the image, instead of choosing File > Export you can instead pick File > Overwrite yourfilename.jpg and it'll just automatically resize and resave, but you lose the "original" file in the process.

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