How to tell if wallpaper resolution scales up/down to another resolution?

How do you calculate whether or not a wallpaper of a certain resolution is also compatible (it scales up/down well) to another resolution?

A scenario might be that you find a wallpaper that you like, but does not have the exact fit size to your monitor's resolution. Naturally you will try to pick a larger resolution wallpaper that is available, but don't know if it will scale down well to the resolution you do have. And by scaling, I mean natural scaling-- where you do not lose out vertically or horizontally.

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If

Hi ÷ Wi = Hm ÷ Wm

then they are the same aspect ratio.

Where H = height, W = width, subscript i is image and subscript m is monitor.

For example: 1920/1080 = 1280/720

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Just beat me by seconds. – SgtOJ Nov 28 '10 at 19:17

Answer: Mathematically. Hight / Width = Hight-to-Width ratio. The wallpaper and your resolution is the same then you are good. Chance are you might not be able to find an exact match. So the closer to your ratio of you screen, the less you will lose from the wallpaper.

Example Math: If resolution is 1920 x 1200 then this is the math: 1920 / 1200 = 1.6. The 1.6 is the hight-to-width ratio. Now just do the same thing with wallpaper.

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That's ridiculous, OF COURSE if the image is the same size as your resolution/monitor/whatever else you want to call it, then you'll be OK.

No one asked if 1 + 1 = 1 + 1.

Scaling up is a no no, it simply does not work with non-vector graphics as Pixelation or stretching will occur which degrades the quality of the image. Vector graphics will scale as they use mathmatical equations to represent the image, which scale. The ratio must remain the same, however.

As @sunpech rightly suggests, it would be best to pick a larger image to scale down, but this will only work if the image aspect is the same (such as 4:3 (standard) or 16:9 (widescreen) which are more commonly known than Brian's suggestion)).

Example scaling:

• 800 x 600 resolution (4:3 aspect) will scale down perfectly well to 640 x 480 (4:3)
• 1920 x 1080 resolution (16:9 aspect) will scale down perfectly well to 1280 x 720 (16:9)
• 2560 x 1600 resolution (16:10 aspect) will scale down perfectly well to 1920 x 1200 (16:10)

a 16:10 won't scale down to a 16:9, while you may get away with it looking OK in some circumstances (1920x1200 to 1920x1080) for example, it is not a true scale down and will most likely have noticeable squashing of the image.

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No one said "1 + 1 = 1 + 1". Both Brian and I suggested ways to calculate whether the ratio of height to width (the aspect ratio - which is what "16:9", for example, means) of an image is the same as that of a monitor. Most people won't know that "1920 x 1080" and "1280 x 720" are both 16:9 just by looking at them. By doing a simple calculation, you can check whether the ratios match for any pixel dimensions even ones that don't match "well-known" dimensions. (Those are division signs in my answer, by the way, not plus signs.) – Dennis Williamson Nov 28 '10 at 20:05
I'm well aware of the difference between a plus and division sign. The equation is identical regardless of the operator. In your example, of which the answer is 1.7 either side of the equation, 1.7 = 1.7, well it's obvious 1.7 equals 1.7, just as 1+1=1+1 (2=2). You didn't explain why you were doing what you were doing which is why I explained further regarding scaling "well". – WoodE Nov 28 '10 at 21:19