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changing resolution in gimp

Nov 6, 2011, 01:07
Post: #1
changing resolution in gimp
I'm trying to use some pictures to design a calendar online and the pictures have to be high resolution to look right. I had no problem changing the resolution on paint shop pro until it decided it crash and never reopen. Now I'm trying to figure out how on earth to do that with gimp. On PSP I just went to image/resize and all I had to do was change the 72 to 300. I'm at loss on how to do it with any other paint or photo program.
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Nov 6, 2011, 01:57
Post: #2
RE: changing resolution in gimp
When you change the resolution from 72 to 300 you get a higher resolution, but a smaller image display... because what really counts is the size in pixels. A 10"x10" image at 300PPI requires 3000x3000 pixels. At 72PPI the same image is only 720x720 pixels. If you want to increase the resolution and keep the same physical size, then someone has to "invent" pixels (in the case above, you go from 720 to 3000, each pixel in the original image has to be replaced by 16 pixels). Image upscaling will only interpolate the existing pixels to create the new pixels but that won't add detail. This will just create an image that looks a bit blurry (if you keep it the same physical size). Usually, when people talk about "high resolution", they really mean "high pixel count", because the resolution is a bit virtual.

You note that I haven't even mentioned Gimp yet because this is true for all bitmap images and the bitmap image editors (Gimp, Photoshop, PSP, Paint.net...)

In Gimp you can set a resolution, but this is only indicative, and is used to display measurements in physical units instead of pixels, and to print output by default. You'll find it in "Image/Print resolution". You'll notice that you can set either the resolution or the print size, but changing one changes the other because they are related though the image size in pixels. If you want to increase the image size in pixels, use "Image/Scale image". If you image is a photo, you can't to much more (but you may find software with improved upscale algorithms that may give slightly better results than Gimp, but don't expect magic...). If your image is more geometric (logo, letters, there are other methods that can give excellent results. See for instance http://gimpforums.com/thread-unpaid-need...ng-3d-text

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