问题
My site is a clothing store, and my partner has complained about the following issue.
The pictures of clothing with more complex patterns (checkerboard for example) displays like this:
instead of this:
I assume the other pictures are also displaying weirdly, but it's just less noticeable. As far as I can tell, it happens most often on Macs.
If anyone has any information about this phenomenon it would be much appreciated.
回答1:
This is called the Moiré effect. From a Wikipedia article:
In physics, mathematics, and art, a moiré pattern (/mwɑrˈeɪ/; French: [mwaˈʁe]) is a secondary and visually evident superimposed pattern created, for example, when two identical (usually transparent) patterns on a flat or curved surface (such as closely spaced straight lines drawn radiating from a point or taking the form of a grid) are overlaid while displaced or rotated a small amount from one another.
In context of images the overlaying comes from anti-aliased (in case of upsampling) or averaged pixels (for downsampling).
To resize them properly use high-quality resizing such as bi-cubic interpolation based resampling. Most browser has built-in support for this but certain conditions are affecting which stratgey is selected (bi-cubic or bi-linear), for example for performance reason. The latter is more prone to this effect.
It can be reduced using a canvas to scale down the image. I have an article here on this topic and an SO answer here showing a concrete example on how to.
回答2:
It's called a Moire Pattern: http://en.wikipedia.org/wiki/Moir%C3%A9_pattern
The best solution is to not resize images, to ensure they're displayed at 1:1 scaling. If not, make differently-sized images using a tool like Photoshop that has better image-resize algorithms that avoid this problem and then use HTML5's srcset attribute so the right image is loaded for the right DPI, see here: http://www.w3.org/html/wg/drafts/srcset/w3c-srcset/
来源：https://stackoverflow.com/questions/22123036/pictures-with-patterns-sometimes-display-strangely