GIMP Version: 2.8
Operating System: Windows
OS Version: 7
GIMP Experience: Intermediate Level

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Hai...

Well I'm curious on how do I resize full images in GIMP?
I have to use my photo-viewer to resize images and I don't think when I resize it keeps transparency.
So I'm really curious how I would go about that in GIMP w/o using the scale tool which can make things more blurry than needed.

Thanks in advance!

~ God Bless ~

~ Moko

I use the scale tool to resize them down but to make them larger, they are going to be blurry.

To resize a full image use "Image/Scale image". Make sure the interpolation algorithm is set to "Sinc/Lanczos". Scaling up is always going to make them blurry. When scaling down:
- You can have artifacts due do "spatial frequency folding": moire patterns, jagged lines... this can be avoided by blurring the image by the scale factor before scaling down (ie, of you scale down 4x (or 25%), apply a Gaussian blur of 4px radius).
- After scaling down (with or without pre-blur), you can apply a bit of sharpening (Unsharp mask).

Will that crop the image?
I don't want it to be cut off just smaller. :3

That won't crop it Moko. It'll just reduce the size.

ofnuts - Thanks for the tip on blurring prior to scaling.

I do not trust Sinc/Lanczos as it results in a corrupted alpha channel*, and this makes me skeptical of its handling of the other channels.

* To see this corruption in action, perform the following.

• Start with any image and flatten it to a single layer.
• Add an alpha channel.
• Examine the histogram of the alpha channel to verify that all pixels have a value of "255".
• Perform an image scale using Sinc/Lanczos (scaling up or down doesn't matter).
• Examine the histogram of the alpha channel and note that somewhere between 30% and 50% of the pixels now have a value of "254".
• If you transfer the alpha channel to a layermask and perform an auto normalize, you can see the pattern of pure white (255) versus off white (254) pixels that is produced.
  
  Attachment:
  
  sinc-alpha-anomaly.png [ 917 Bytes | Viewed 3904 times ]
  

While this is not a lot of error (<0.4%), it is disconcerting.

Actually it's the same problem if you scale a plain white image. The result is not plain white, but has the same pattern. But this show up only in very uniform areas.

Thank you for the help everyone! :3