How to avoid this?

[f55user]

Notice the stairs.... when the pic was resized all the moire or whatever it is comes out... it happens whether i sharpen the picture or not. How to avoid this effect?

 

[Del_CtrlnoAlt]

abit of beginner talk.. take a bigger pic, to capture the durian den cut away the stairs to become a panorama shot?

 

[Zerstorer]

Stick to 1/2,1/4,1/8 (50%, 25%, 12.5%) resizing ratios and see if it helps.

 

[f55user]

yes the "even" ratios help but then the pic either ends up too small or too big.. the source only 2.1MP.. thanks for suggestions anyway

 

[Ng Pei Sin]

try resizing with Photoshop.

 

[fruitybix]

This is something that i doubt you could make it go way. It is called "moire effect". it is the CCD's ability to resolve lines, whether it be close to each other, or curves, where you may see "jaggies" on the curves. Some CCDs can resolve this very well, as to keep the lines clear, sharp and distinct. But if you blow up this picture, you will see less of this effect.

 

[f55user]

1) already used photoshop.
2) the moire is not there in the original....

anyway the "even" resizing ratios have the most effect..

 

[Zerstorer]

Originally posted by fruitybix
This is something that i doubt you could make it go way. It is called "moire effect". it is the CCD's ability to resolve lines, whether it be close to each other, or curves, where you may see "jaggies" on the curves. Some CCDs can resolve this very well, as to keep the lines clear, sharp and distinct. But if you blow up this picture, you will see less of this effect.

Actually what he is trying to resolve is aliasing and not moire.

Moire are interference patterns occuring in high frequency picture elements(high resolution).

What he has is aliasing or stair-stepping which is caused by insufficient pixel resolution to represent a angled line properly. Odd or fractional resizing ratios will exaggerate the problem, while even ratios will keep it to a bare minimum.

The only way to reduce it is to use some resampling algorithm which applies some for of filtering or smoothening algorithm(bicubic is one, perhaps you can try Genuine Fractals or B-spline), perhaps at the expense of some details.

Think of Anti-aliasing for 3D games and you should get the idea.

 

[mylau]

try resizing in many small steps instead of one big step

 

[Zerstorer]

Originally posted by mylau
try resizing in many small steps instead of one big step

Worth a try.

Record an action in Photoshop and set image size to 5% increment/decrement as many times until u reach the size you need.(Free Stair Interpolation action)

Or you can try the Lanzcos algorithm in Irfranview.

 

[fruitybix]

thanks for the info :thumbsup:

 

[Bedpan]

Agree, Try Irfanview! Free Free Free

Originally posted by Zerstorer
Worth a try.

Record an action in Photoshop and set image size to 5% increment/decrement as many times until u reach the size you need.(Free Stair Interpolation action)

Or you can try the Lanzcos algorithm in Irfranview.